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                                  THE

                            WONDERS OF LIFE

                            A POPULAR STUDY
                       OF BIOLOGICAL PHILOSOPHY

                                  BY

                             ERNST HAECKEL
           (Ph.D., M.D., LL.D., Sc.D., and Professor at the
                          University of Jena)

                               AUTHOR OF
                     "THE RIDDLE OP THE UNIVERSE"
                       "THE HISTORY OF CREATION"
                        "THE EVOLUTION OF MAN"
                                 ETC.

                             TRANSLATED BY
                             JOSEPH McCABE

                        SUPPLEMENTARY VOLUME TO
                     "THE RIDDLE OF THE UNIVERSE"

  [Illustration: LOGO]

                     HARPER & BROTHERS PUBLISHERS

                          NEW YORK AND LONDON

                                 1905




                Copyright, 1904, by HARPER & BROTHERS.

                        _All rights reserved._

                       Published January, 1905.




                               CONTENTS


                   PART I.--METHODOLOGICAL SECTION:
                           KNOWLEDGE OF LIFE

                                         PAGE

  PREFACE                                   v

  CHAPTER I

  TRUTH                                     1


  CHAPTER II

  LIFE                                     27


  CHAPTER III

  MIRACLES                                 54


  CHAPTER IV

  THE SCIENCE OF LIFE                      77


  CHAPTER V

  DEATH                                    97


                   PART II.--MORPHOLOGICAL SECTION:
                            NATURE OF LIFE


  CHAPTER VI

  PLASM                                   121


  CHAPTER VII

  UNITIES OF LIFE                         147


  CHAPTER VIII

  FORMS OF LIFE                           170


  CHAPTER IX

  MONERA                                  190


                   PART III.--PHYSIOLOGICAL SECTION:
                           FUNCTIONS OF LIFE


  CHAPTER X

  NUTRITION                               210


  CHAPTER XI

  REPRODUCTION                            239


  CHAPTER XII

  MOVEMENT                                258


  CHAPTER XIII

  SENSATION                               287


  CHAPTER XIV

  MENTAL LIFE                             315


                    PART IV.--GENEALOGICAL SECTION:
                            HISTORY OF LIFE


  CHAPTER XV

  THE ORIGIN OF LIFE                      336


  CHAPTER XVI

  THE EVOLUTION OF LIFE                   359


  CHAPTER XVII

  THE VALUE OF LIFE                       386


  CHAPTER XVIII

  MORALITY                                411


  CHAPTER XIX

  DUALISM                                 433


  CHAPTER XX

  MONISM                                  452


  INDEX                                   475




PREFACE


The publication of the present work on _The Wonders of Life_ has been
occasioned by the success of _The Riddle of the Universe_, which I
wrote five years ago. Within a few months of the issue of this study
of the monistic philosophy, in the autumn of 1899, ten thousand copies
were sold. Moreover, the publisher having been solicited on many sides
to issue a popular edition of the work, more than a hundred thousand
copies of this were sold within a year.[1] This extraordinary and--as
far as I was concerned--unexpected success of a philosophical work
which was by no means light reading, and which had no particular charm
of presentation, affords ample proof of the intense interest taken by
even the general reader in the object of the work--the construction of
a rational and solid philosophy of life.

Naturally, the clear opposition of my monistic philosophy, based
as it was on the most advanced and sound scientific knowledge, to
the conventional ideas and to an outworn "revelation," led to the
publication of a vast number of criticisms and attacks. During the
first twelve months more than a hundred reviews and a dozen large
pamphlets appeared, full of the most contradictory strictures and the
most curious observations. One of the ablest of my pupils, Heinrich
Schmidt, gave a summary and criticism of them in his _Der Kampf
um die Welträthsel_, in the autumn of 1900. However, the literary
struggle went on to assume gigantic proportions when twelve different
translations of the _Riddle_ appeared, and led to an ever-increasing
agitation in every educated country of the Old and the New World.

I gave a brief reply to the chief of these attacks in April, 1903,
in the appendix to the popular edition of the _Riddle_. It would be
useless to go further into this controversy and meet the many attacks
that have since been made. It is a question here of that profound
and irreconcilable opposition between knowledge and faith, between
a real knowledge of nature and an alleged "revelation," which has
occupied the thoughtful and inquiring mind for thousands of years.
I base my monistic philosophy exclusively on the convictions which
I have gained during fifty years' close and indefatigable study of
nature and its harmonious working. My dualistic opponents grant only a
restricted value to these experiences; they would subordinate them to
the fantastic ideas which they have reached by faith in a supernatural
world of spirits. An honest and impartial consideration of this
palpable contradiction discovers it to be irreconcilable--_either_
science and experience, or faith and revelation!

For this reason I do not propose to make any further reply to the
opponents of _The Riddle of the Universe_, and I am still less disposed
to take up the personal attacks which some of my critics have thought
fit to make on me. In the course of this controversy I have grown
painfully familiar with the means with which it is sought to silence
the detested free-thinker--misrepresentation, sophistry, calumny, and
denunciation. "Critical" philosophers of the modern Kantist school
vie in this with orthodox theologians. What I have said in this
connection of the theologian Loofs, of Halle, the philologist Dennert,
of Godesberg, and the metaphysician Paulsen, of Berlin, in the appendix
to the cheap German edition of the _Riddle_, applies equally to many
other opponents of the same type. These heated partisans may continue
to attack and calumniate my person as they will; they will not hurt the
sacred cause of truth in which I labor.

Much more interesting to me than these attacks were the innumerable
letters which I have received from thoughtful readers of the _Riddle_
during the last five years, and particularly since the appearance
of a popular edition. Of these I have already received more than
five thousand. At first I conscientiously replied to each of these
correspondents, but I had at length to content myself with sending
a printed slip with the intimation that my time and strength did
not permit me to make an adequate reply. However, though this
correspondence was very exacting, it afforded a very welcome proof of
the lively sympathy of a large number of readers with the aim of the
monistic philosophy, and a very interesting insight into the mental
attitude of the most varied classes of readers. I especially noticed
that the same remarks and questions occurred in many of these five
thousand letters, very often expressed in the same terms. Most of the
inquiries related to biological questions, which I had cursorily and
inadequately touched both in _The Riddle of the Universe_ and _The
History of Creation_. The natural desire to remedy these deficiencies
of my earlier writings and give a general reply to my interrogators was
the immediate cause of the writing of the present work on _The Wonders
of Life_.

I was confirmed in this design by the circumstance that another
scientist, the botanist Johannes Reinke, of Kiel, had published
two works in which he had treated the general problems of natural
philosophy, especially of biology, from a purely dualistic and
teleological point of view; these works were his _Die Welt als That_
(1899) and _Einleitung in die theoretische Biologie_ (1902). As both
these works are well written and present the principles of dualism and
teleology with admirable consistency--as far as this is possible--it
seemed to me that it was desirable to give a thorough exposition of my
own monistic and causative system.

Hence the present work on the wonders of life is, as the title
indicates, a supplementary volume to _The Riddle of the Universe_.
While the latter undertook to make a comprehensive survey of the
general questions of science--as cosmological problems--in the light
of the monistic philosophy, the present volume is confined to the
realm of organic science, or the science of life. It seeks to deal
connectedly with the general problems of biology, in strict accord with
the monistic and mechanical principles which I laid down in 1866 in my
_General Morphology_. In this I laid special stress on the universality
of the law of substance and the substantial unity of nature, which I
have further treated in the second and fourteenth chapters of _The
Riddle of the Universe_.

The arrangement of the vast material for this study of the wonders
of life has been modelled on that of the _Riddle_. I have retained
the division into larger and smaller sections and the synopses of
the various chapters. Thus the whole biological content falls into
four sections and twenty chapters. I should much have liked to add
illustrations in many parts of the text to make the subject plainer,
especially as regards chapters vii., viii., xi., and xvi.; but this
would have led to a considerable increase in the size and price of
the book. Moreover, there are now many illustrated works which will
help the reader to go more fully into the various sections of the
study. Among others, my _History of Creation_ (English translation) and
_Evolution of Man_ (English translation now in course of preparation)
will be found helpful in this way. The German reader will also find
many illustrations to elucidate the text of this book in my recently
completed work, _Kunstformen der Natur_ (10 parts, with 100 tables,
1899-1904).

I had said, in the preface to _The Riddle of the Universe_ in 1899,
that I proposed to close my study of the monistic system with that
work, and that "I am wholly a child of the nineteenth century, and
with its close I draw the line under my life's work." If I now seem
to run counter to this observation, I beg the reader to consider that
this work on the wonders of life is a _necessary_ supplement to the
widely circulated _Riddle of the Universe_, and that I felt bound to
write it in response to the inquiries of so many of my readers. In this
second work, as in the earlier one, I make no pretension to give the
reader a comprehensive statement of my monistic philosophy in the full
maturity it has reached--for me personally, at least--at the close of
the nineteenth century. A subjective theory of the world such as this
can, naturally, never hope to have a complete objective validity. My
knowledge is incomplete, like that of all other men. Hence, even in
this "biological sketch-book," I can only offer studies of unequal
value and incomplete workmanship. There still remains the great design
of embracing all the exuberant phenomena of organic life in one general
scheme and explaining all the wonders of life from the monistic point
of view, as forms of one great harmoniously working universe--whether
you call this Nature or Cosmos, World or God.

The twenty chapters of _The Wonders of Life_ were written
uninterruptedly in the course of four months which I spent at Rapallo,
on the shore of the blue Mediterranean. The quiet life in this tiny
coast-town of the Italian Riviera gave me leisure to weigh again all
the views on organic life which I had formed by many-sided experience
of life and learning since the beginning of my academic studies (1852)
and my teaching at Jena (1861). To this I was stimulated by the
constant sight of the blue Mediterranean, the countless inhabitants
of which had, for fifty years, afforded such ample material for my
biological studies; and my solitary walks in the wild gorges of the
Ligurian Apennines, and the moving spectacle of its forest-crowned
mountain altars, inspired me with a feeling of the unity of living
nature--a feeling that only too easily fades away in the study of
detail in the laboratory. On the other hand, such a situation did not
allow a comprehensive survey of the boundless literature which has been
evoked by the immense advances in every branch of biology. However,
the present work is not intended to be a systematic manual of general
biology. In the revision of the text, on which I was engaged during
the summer at Jena, I had to restrict myself to occasional additions
and improvements. In this I had the assistance of my worthy pupil, Dr.
Heinrich Schmidt, to whom also I am indebted for the careful revision
of the proofs.

When I completed my seventieth year at Rapallo, on February 16th, I
was overwhelmed with a mass of congratulations, letters, telegrams,
flowers, and other gifts, most of which came from unknown readers of
_The Riddle of the Universe_ in all parts of the world. If my thanks
have not yet reached any of them, I beg to tender them in these lines.
But I should be especially gratified if they would regard this work on
the wonders of life as an expression of my thanks, and as a literary
gift in return. May my readers be moved by it to penetrate deeper and
deeper into the glorious work of Nature, and to reach the insight of
our greatest German natural philosopher, Goethe:

  "What greater thing in life can man achieve
  Than that God-Nature be revealed to him?"

  ERNST HAECKEL.

  JENA, _June 17, 1904_.




THE WONDERS OF LIFE




THE WONDERS OF LIFE




I

TRUTH

 Truth and the riddle of the universe--Experience
 and thought--Empiricism and speculation--Natural
 philosophy--Science--Empirical science--Descriptive
 science--Observation and experiment--History and
 tradition--Philosophic science--Theory of knowledge--Knowledge
 and the brain--Æstheta and phroneta--Seat of the soul, or
 organ of thought: phronema--Anatomy, physiology, ontogeny, and
 phylogeny of the phronema--Psychological metamorphoses--Evolution
 of consciousness--Monistic and dualistic theories of
 knowledge--Divergence of the two ways of attaining the truth.


What is truth? This great question has occupied the more thoughtful of
men for thousands of years, and elicited myriads of attempts to answer
it, myriads of truths and untruths. Every history of philosophy gives a
longer or shorter account of these countless efforts of the advancing
mind of man to attain a clear knowledge of the world and of itself.
Nay, even "world-wisdom" itself, or philosophy in the proper sense
of the word, is nothing but a connected effort to unite the general
results of man's investigation, observation, reflection, and thought,
and bring them to a common focus. Without prejudice and without fear,
philosophy would tear the mantle from "the veiled statue of Sais," and
attain a full vision of the truth. True philosophy, taken in this
sense, may proudly and justly style itself "the queen of the sciences."

When philosophy, as a search for truth in the highest sense, thus
unites our isolated discoveries and seeks to weld them into one unified
system of the world, it comes at length to state certain fundamental
problems, the answer to which varies according to the degree of culture
and the point of view of the inquirer. These final and highest objects
of scientific inquiry have been of late comprehended under the title
of _The Riddle of the Universe_, and I gave this name to the work I
published in 1899, which dealt with them, in order to make its aim
perfectly clear. In the first chapter I dealt briefly with what have
been called "the seven great cosmic problems," and in the twelfth
chapter I endeavored to show that they may all be reduced to one
final "problem of substance," or one great "riddle of the universe."
The general formulation of this problem is effected by blending the
two chief cosmic laws--the chemical law of the constancy of matter
(Lavoisier, 1789), and the physical law of the constancy of force
(Robert Mayer, 1842). This monistic association of the two fundamental
laws, and establishment of the unified law of substance, has met with
a good deal of agreement, but also with some opposition; but the most
violent attacks were directed against my monistic theory of knowledge,
or against the method I followed in seeking to solve the riddle of
the universe. The only paths which I had recognized as profitable
were those of experience and thought--or empirical knowledge and
speculation. I had insisted that these two methods supplemented each
other, and that they alone, under the direction of reason, lead to the
attainment of truth. At the same time I had rejected as false two other
much-frequented paths which purported to lead directly to a profounder
knowledge, the ways of emotion and revelation; both of these are in
opposition to reason, since they demand a belief in miracles.

"All natural science is philosophy, and all true philosophy is natural
science. All true science is natural philosophy." I expressed in
these words the general result of my monistic studies in 1866 (in the
twenty-seventh chapter of my _Generelle Morphologie_). I then laid it
down as the fundamental principle of the monistic system that the unity
of nature and the unity of science follow absolutely from any connected
study of modern philosophic science, and I expressed my conviction
in these terms: "All human science is knowledge based on experience,
or empirical philosophy; or, if the title be preferred, philosophic
empiricism. Thoughtful experience, or thought based on experience, is
the only way and method to be followed in the search for truth." I
endeavored to establish these theses conclusively in the first book
of the _Generelle Morphologie_, which contains (p. 108) a critical
and methodological introduction to this science. Not only are those
methods considered "which must necessarily supplement each other" (I.
Empiricism and Philosophy; II. Analysis and Synthesis; III. Induction
and Deduction), but also those "which necessarily exclude each other"
(IV. Dogmatism and Criticism; V. Teleology and Causality, or Vitalism
and Mechanicism; VI. Dualism and Monism). The monistic principles which
I developed there thirty-eight years ago have only been confirmed by
my subsequent labors, and so I may refer the interested reader to
that work. _The Riddle of the Universe_ is in the main an attempt to
introduce to the general reader in a convenient form the chief points
of the monistic system I established. However, the opposition which has
been aroused by the general philosophic observations of the _Riddle_
compels me to give a further explanation of the chief features of my
theory of knowledge.

All true science that deserves the name is based on a collection of
experiences, and consists of conclusions that have been reached by
a rational connection of these experiences. "Only in experience is
there truth," says Kant. The external world is the object that acts
on man's organs of sense, and in the internal sense-centres of the
cortex of the brain these impressions are subjectively transformed into
presentations. The thought-centres, or association centres, of the
cortex (whether or no one distinguishes them from the sense-centres)
are the real organs of the mind that unite these presentations into
conclusions. The two methods of forming these conclusions--induction
and deduction, the formation of arguments and concepts, thought and
consciousness--make up together the cerebral function we call reason.
These long familiar and fundamental truths, the recognition of which
I have described for thirty-eight years as the first condition for
solving the riddle of life, are still far from being generally
appreciated. On the contrary, we find them combated by the extreme
representatives of both tendencies of science. On the one side, the
empirical and descriptive school would reduce the whole task to
experience, without calling in the aid of philosophy; while philosophic
speculation, on the other side, would dispense with experience and
endeavor to construct the world by pure thought.

Starting from the correct principle that all science originally has its
source in experience, the representatives of "experimental science"
affirm that their task consists solely in the exact observation of
"facts" and the classification and description of them, and that
philosophic speculation is nothing more than an idle play of ideas.
Hence this one-sided sensualism, as Condillac and Hume especially
maintained it, affirmed that the whole action of the mind consists in
a manipulation of sense-impressions. This narrow empirical conception
spread very widely during the nineteenth century, particularly in the
second half, among the rapidly advancing sciences; it was favored by
the specialism which grew up in the necessary division of labor. The
majority of scientists are still of opinion that their task is confined
to the exact observation and description of facts. All that goes beyond
this, and especially all far-reaching philosophic conclusions from
their accumulated observations, are regarded by them with suspicion.
Rudolph Virchow strongly emphasized this narrow empirical tendency ten
years ago. In his speech on the foundation of the Berlin University
he explained the "transition from the philosophic to the scientific
age"; he said that the sole aim of science is "the knowledge of
facts, the objective investigation of natural phenomena in detail."
The former politician seemed to forget that he had maintained a
precisely opposite view forty years before (at Würtzburg), and that
his own great achievement, the creation of cellular pathology, was a
philosophic construction--the formation of a new and comprehensive
theory of disease by the combination of countless observations and the
conclusions deduced therefrom.

No science of any kind whatever consists solely in the description of
observed facts. Hence we can only regard it as a pitiful contradiction
in terms when we find biology classed in official documents to-day as
a "descriptive science," and physics opposed to it as an "explanatory
science." As if in both cases we had not, after describing the observed
phenomena, to pass on to trace them to their causes--that is, to
_explain_ them--by means of rational inferences! But it is even more
regrettable to find that one of the ablest scientists of Germany,
Gustav Kirchhoff, has claimed that description is the final and the
highest task of science. The famous discoverer of spectrum analysis
says in his _Lectures on Mathematical Physics and Mechanics_
(1877): "It is the work of science to describe the movements perceived
in Nature, in the most complete and simplest fashion." There is no
meaning in this statement unless we take the word "description" in a
quite unusual sense--unless "complete description" is meant to include
explanation. For thousands of years true science has been, not merely
a simple description of individual facts, but an explanation of them
by tracing them to their causes. It is true that our knowledge of them
is always imperfect, or even hypothetical; but this is equally true
of the description of facts. Kirchhoff's statement is in flagrant
contradiction to his own great achievement, the founding of spectrum
analysis; for the extraordinary significance of this does not lie in
the discovery of the wonderful facts of spectroscopic optics and the
"complete description" of individual spectra, but in the rational
grouping and interpretation of them. The far-reaching conclusions that
he has drawn from them have opened out entirely new paths to physics
and chemistry. Hence Kirchhoff is in as sad a plight as Virchow when
he formulates so precarious a principle. However, these statements of
the two great scientists have done a great deal of harm, as they have
widened still more the deep gulf between science and philosophy. It
may be of some service if a few thousand of the thoughtless followers
of "descriptive science" are persuaded to refrain from attempts at
explanation of facts. But the master-builders of science cannot be
content with the collection of dead material; they must press on to the
knowledge of causes by a rational manipulation of their facts.

The accurate and discriminating observation of facts, supported by
careful experiment, is certainly a great advantage that modern science
has over all earlier efforts to attain the truth. The distinguished
thinkers of classic antiquity were far superior to most modern
scientists and philosophers in regard to judgment and reasoning, or
all the subtler processes of thought; but they were superficial and
unpractised observers, and were barely acquainted with experiment.
In the Middle Ages scientific work degenerated in both its aspects,
as the dominant creed demanded only faith and the recognition of
its supernatural revelation, and depreciated observation. The great
importance of this as a foundation of real knowledge was first
appreciated by Bacon of Verulam, whose _Novum Organon_ (1620) laid down
the principles of scientific knowledge, in opposition to the current
scholasticism derived from Aristotle and his _Organon_. Bacon became
the founder of modern empirical investigation, not only by making
careful and exact observation of phenomena the basis of all philosophy,
but also in demanding the supplementing of this by experiment; by
this experiment he understood the putting of a question to Nature, as
it were, which she must herself answer--a kind of observation under
definite and deliberate conditions.

This more rigorous method of "exact observation," which is hardly
three hundred years old, was very strongly aided by the inventions
which enable the human eye to penetrate into the farthest abysses of
space and the profoundest depths of smaller bodies--the telescope and
microscope. The great improvement in these instruments during the
nineteenth century, and the support given by other recent inventions,
have led to triumphs of observation in this "century of science"
that surpassed all anticipation. However, this very refinement of
the technique of observation has its drawbacks, and has led to many
an error. The effort to obtain the utmost accuracy in _objective_
observation has often led to a neglect of the part which is played by
the _subjective_ mental action of the observer; his judgment and reason
have been depreciated in comparison with the acuteness and clearness
of his vision. Frequently the means has been turned into the end of
knowledge. In the reproduction of the thing observed the objective
photograph, presenting all parts of the object with equal plainness,
has been more valued than the subjective design that reproduces only
what is essential and leaves out what is superfluous; yet the latter
is in many cases (for instance, in histological observation) much more
important and correct than the former. But the greatest fault has been
that many of these "exact" observers have refrained altogether from
reflection and judgment on the phenomena observed, and have neglected
subjective criticism; hence it is that so often a number of observers
of the same phenomenon contradict each other, while each one boasts of
the "exactness" of his observations.

Like observation, experimentation has been wonderfully improved
of late years. The experimental sciences which make most use of
it--experimental physics, chemistry, physiology, pathology, etc.--have
made astounding progress. But it is just as important in the case of
experiment--or observation under artificial conditions--as of simple
observation that it be undertaken and carried out with a sound and
clear judgment. Nature can only give a correct and unambiguous answer
to the question you put it when it is clearly and distinctly proposed.
This is very often not the case, and the experimenter loses himself in
meaningless efforts, with the foolish hope that "something may come
of it." The modern province of experimental or mechanical embryology
is especially marred by these useless and perverse experiments.
Equally foolish is the conduct of those biologists who would transfer
the experiment that is valuable in physiology to the field of
anatomy, where it is rarely profitable. In the modern controversy
about evolution the attempt is frequently made to prove or refute
experimentally the origin of species. It is quite forgotten that the
idea of species is only relative, and that no man of science can give
an absolute definition of it. Nor is it less perverse to attempt to
apply experimentation to historical problems where all the conditions
for a successful application are lacking.

The knowledge which we obtain directly by observation and experiment is
only sound when it refers to present events. We have to turn to other
methods for the investigation of the past--to history and traditions;
and these are less easily accessible. This branch of science has been
investigated for thousands of years, as far as the history of man
and civilization, of peoples and states, and their customs, laws,
languages, and migrations, is concerned. In this, the oral and written
tradition from generation to generation, the ancient monuments, and
documents, and weapons, etc., furnish an abounding empirical material
from which critical judgment can draw a host of conclusions. However,
the door to error lies wide open here, as the documents are usually
imperfect, and the subjective interpretation of them is often no
clearer than their objective validity.

Natural history, properly so called, or the study of the origin and
past history of the universe, the earth, and its organic population,
is much more recent than the history of mankind. Immanuel Kant was
the first to lay the foundations of a mechanical cosmogony in his
remarkable _Natural History of the Heavens_ (1755), and Laplace gave
mathematical shape to his ideas in 1796. Geology, also, or the story of
the evolution of the earth, was not founded until the beginning of the
eighteenth century, and did not assume a definite shape until the time
of Hoff and Lyell (1830). Later still (1866) were laid the foundations
of the science of organic evolution, when Darwin provided a sound
foundation, in his theory of selection, for the theory of descent
which Lamarck had proposed fifty years before.

In sharp contrast to this purely empirical method, which is favored
by most men of science in our day, we have the purely speculative
tendency which is current among our academic philosophers. The great
regard which the critical philosophy of Immanuel Kant obtained during
the nineteenth century has recently been increased in the various
schools of philosophy. As is known, Kant affirmed that only a part of
our knowledge is empirical, or _a posteriori_--that is, derived from
experience; and that the rest of our knowledge (as, for instance,
mathematical axioms) is _a priori_--that is to say, reached by the
deductions of pure reason, independently of experience. This error
led to the further statement that the foundations of science are
metaphysical, and that, though man can attain a certain knowledge
of phenomena by the innate forms of space and time, he cannot grasp
the "thing in itself" that lies behind them. The purely speculative
metaphysics which was built up on Kant's apriorism, and which found its
extreme representative in Hegel, came at length to reject the empirical
method altogether, and insisted that all knowledge is obtained by pure
reason, independently of experience.

Kant's chief error, which proved so injurious to the whole of
subsequent philosophy, lay in the absence of any physiological and
phylogenetic base to his theory of knowledge; this was only provided
sixty years after his death by Darwin's reform of the science of
evolution, and by the discoveries of cerebral physiologists. He
regarded the human mind, with its innate quality of reason, as a
completely formed entity from the first, and made no inquiry into
its historical development. Hence, he defended its immortality as a
practical postulate, incapable of proof; he had no suspicion of the
evolution of man's soul from that of the nearest related mammals.
The curious predisposition to _a priori_ knowledge is really the
effect of the inheritance of certain structures of the brain, which
have been formed in man's vertebrate ancestors slowly and gradually,
by adaptation to an association of experiences, and therefore of
_a posteriori_ knowledge. Even the absolutely certain truths of
mathematics and physics, which Kant described as synthetic judgments _a
priori_, were originally attained by the phyletic development of the
judgment, and may be reduced to constantly repeated experiences and
_a priori_ conclusions derived therefrom. The "necessity" which Kant
considered to be a special feature of these _a priori_ propositions
would be found in all other judgments if we were fully acquainted with
the phenomena and their conditions.

Among the censures which the academic metaphysicians, especially in
Germany, have passed on my _Riddle of the Universe_, the heaviest
is perhaps the charge that I know nothing whatever about the theory
of knowledge. The charge is correct to this extent, that I do _not_
understand the current dualistic theory of knowledge which is based
on Kant's metaphysics; I cannot understand how their introspective
psychological methods--disdaining all physiological, histological, or
phylogenetic foundations--can satisfy the demands of "pure reason." My
monistic theory of knowledge is assuredly very different from this.
It is firmly and thoroughly based on the splendid advances of modern
physiology, histology, and phytogeny--on the remarkable results of
these empirical sciences in the last forty years, which are entirely
ignored by the prevailing system of metaphysics. It is on the ground of
these experiences that I have adopted the views on the nature of the
human mind which are expounded in the second part of _The Riddle of the
Universe_ (chapters vi.-xi.). The following are the chief points:

1. The soul of man is--objectively considered--essentially similar
to that of all other vertebrates; it is the physiological action or
function of the brain.

2. Like the functions of all other organs, those of the brain are
effected by the cells, which make up the organ.

3. These brain-cells, which are also known as soul-cells, ganglionic
cells, or neurona, are real nucleated cells of a very elaborate
structure.

4. The arrangement and grouping of these psychic cells, the number of
which runs into millions in the brain of man and the other mammals, is
strictly regulated by law, and is distinguished within this highest
class of the vertebrates by several characteristics, which can only be
explained by the common origin of the mammals from one primitive mammal
(or pro-mammal of the Triassic period).

5. Those groups of psychic cells which we must regard as the agents of
the higher mental functions have their origin in the fore-brain, the
earliest and foremost of the five embryonic brain-vesicles; they are
confined to that part of the surface of the fore-brain which anatomists
call the cortex, or gray bed, of the brain.

6. Within the cortex we have localized a number of different mental
activities, or traced them to certain regions; if the latter are
destroyed, their functions are extinguished.

7. These regions are so distributed in the cortex that one part of
them is directly connected with the organs of sense, and receives
and elaborates the impressions from these: these are the inner
sense-centres, or sensoria.

8. Between these central organs of sense lie the intellectual
or thought-organs, the instruments of presentation and thought,
judgment and consciousness, intellect and reason; they are called
the thought-centres, or association-centres, because the various
impressions received from the sense-centres are associated, combined,
and united in harmonious thought by them.[2]

The anatomic distinction between the two regions of the cortex
which we oppose to each other as the internal sense-centres and the
thought or association-centres seems to me of the highest importance.
Certain physiological considerations had for some time suggested
this distinction, but the sound anatomic proof of it has only been
furnished during the last ten years. In 1894 Flechsig showed that
there are four central sense-regions ("internal sense-spheres," or
æstheta) in the gray cortex of the brain, and four thought-centres
("association-centres" or phroneta) between these: the most important
of the latter, from the psychological point of view, is the "principal
brain," or the "great occipito-temporal association-centre." The
anatomic determination of the two "psychic regions" which Flechsig
first introduced was afterwards modified by himself and substantially
altered by others. The distinguished works of Edinger, Weigert,
Hitzig, and others, lead to somewhat discrepant conclusions. But
for the general conception of psychic action, and especially of
the cognitive functions, which interests us at present, it is not
necessary to have this delimitation of the regions. The chief point
holds, that we can to-day anatomically distinguish between the two
most important organs of mental life; that the neurona, which compose
both, differ histologically (or in finer structure) and ontogenetically
(or in origin); and that even chemical differences (or a different
relation to certain coloring matters) may be perceived. We may
conclude from this that the neurona or psychic cells which compose
both organs also differ in their finer structure; there is probably a
difference in the complicated fibrils which extend in the cytoplasm
of both organs, although our coarse means of investigation have not
yet succeeded in detecting this difference. In order to distinguish
properly between the two sets of neurona, I propose to call the
sensory-cells or sense-centres _æsthetal cells_, and the thought-cells
or thought-centres _phronetal cells_. The former are, anatomically and
physiologically, the intermediaries between the external sense-organs
and the internal thought-organs.

To this anatomic delimitation of the internal sense-centres and
thought-organs in the cortex corresponds their physiological
differentiation. The sensorium, or sense-centre, works up the external
sense-impressions that are conveyed by the peripheral sense-organs
and the specific energy of their sensory nerves; the _æstheta_, or
the central sense-instruments that make up the sensorium, and their
organic units, the _æsthetal cells_, prepare the sense-impressions for
thought and judgment in the proper sense. This work of "pure reason" is
accomplished by the _phronema_ of the thought-centres, the _phroneta_
(or the various thought-organs that compose it) and their histological
elements, the phronetal cells, bringing about an association or
combination of the prepared impressions. By this important distinction
we avoid the error of the older sensualism (of Hume, Condillac,
etc.)--namely, that all knowledge depends on sense-action alone. It
is true that the senses are the original source of all knowledge;
but, in order to have real knowledge and thought, the specific task
of reason, the impressions received from the external world by the
sense-organs, and their nerves and centres, must be combined in the
association-centres and elaborated in the conscious thought-centres.
Then there is the important, but frequently overlooked, circumstance
that there is in advance in the phronetal cells of the civilized man
a valuable quality in the shape of inherited potential nerve-energy,
which was originally engendered by the actual sense-action of the
æsthetal cells in the course of many generations.

An impartial and critical study of the action of the brain in
various scientific leaders shows that, as a rule, there is a certain
opposition, or an antagonistic correlation, between the two sections
of the highest mental power. The empirical representatives of science,
or those who are devoted to physical studies, have a preponderant
development of the sensorium, which means a greater disposition and
capacity for the observation of phenomena in detail. On the other hand,
the speculative representatives of what is called mental science and
philosophy, or of metaphysical studies, have the phronema more strongly
developed, which means a preponderant tendency to, and capacity for,
a comprehensive perception of the universal in particulars. Hence it
is that metaphysicians usually look with disdain on "materialistic"
scientists and observers; while the latter regard the play of ideas
of the former as an unscientific and speculative dissipation.
This physiological antagonism may be traced histologically to the
comparative development of the æsthetal and the phronetal cells in
the two cases. It is only in natural philosophers of the first rank,
such as Copernicus, Newton, Lamarck, Darwin, and Johannes Müller, that
both sections are harmoniously developed, and thus the individual is
equipped for the highest mental achievements.

If we take the ambiguous term "soul" (_psyche_ or _anima_) in the
narrower sense of the higher mental power, we may assign as its
"seat" (or, more correctly, its organ), in man and the other mammals,
that part of the cortex which contains the phroneta and is made up
of the phronetal cells; a short and convenient name for this is the
_phronema_. According to our monistic theory, the phronema is the
organ of thought in the same sense in which we consider the eye the
organ of vision, or the heart the central organ of circulation. With
the destruction of the organ its function disappears. In opposition
to this biological and empirically grounded theory, the current
metaphysical psychology regards the brain as the seat of the soul,
only in a very different sense. It has a strictly dualistic conception
of the human soul as a being apart, only dwelling in the brain (like
a snail in its shell) for a time. At the death of the brain it is
supposed to live on, and indeed for all eternity. The immortal soul,
on this theory (which we can trace to Plato), is an immaterial entity,
feeling, thinking, and acting independently, and only using the
material body as a temporary implement. The well-known "piano-theory"
compares the soul to a musician who plays an interesting piece (the
individual life) on the instrument of the body, and then deserts it, to
live forever on its own account. According to Descartes, who insured
the widest acceptance for Plato's dualistic mysticism, the proper
habitation of the soul in the brain--in the music-room--is the pineal
gland, a posterior section of the middle-brain (the second embryonic
cerebral vesicle). The famous pineal gland has lately been recognized
by comparative anatomists as the rudiment of a single organ of vision,
the pineal eye (which is still found in certain reptiles). Moreover,
not one of the innumerable psychologists who seek the seat of the
soul in some part of the body, after the fashion of Plato, has yet
formulated a plausible theory of the connection of mind and body and
the nature of their reciprocal action. On our monistic principles the
answer to this question is very simple, and consonant with experience.
In view of its extreme importance, it is advisable to devote at least a
few lines to the consideration of the phronema in the light of anatomy,
physiology, ontogeny, and phylogeny.

When we conceive the phronema as the real "organ of the soul" in the
strict sense--that is to say, as the central instrument of thought,
knowledge, reason, and consciousness--we may at once lay down the
principle that there is an anatomical unity of organ corresponding
to the physiological and generally admitted unity of thought and
consciousness. As we assign to this phronema a most elaborate
anatomical structure, we may call it the organic apparatus of the
soul, in the same sense in which we conceive the eye as a purposively
arranged apparatus of vision. It is true that we have as yet only made
a beginning of the finer anatomic analysis of the phronema, and are not
yet able to mark off its field decisively from the neighboring spheres
of sense and motion. With the most improved means of modern histology,
the most perfect microscopes and coloring methods, we are only just
beginning to penetrate into the marvellous structure of the phronetal
cells and their complicated grouping. Yet we have advanced far enough
to regard it as the most perfect piece of cell-machinery and the
highest product of organic evolution. Millions of highly differentiated
phronetal cells form the several stations of this telegraphic system,
and thousands of millions of the finest nerve-fibrils represent
the wires which connect the stations with one another and with the
sense-centres on the one hand, and with the motor-centres on the other.
Comparative anatomy, moreover, acquaints us with the long and gradual
development which the phronema has undergone within the higher class
of the vertebrates, from the amphibia and reptiles up to the birds and
mammals, and, within the last class, from the monotremes and marsupials
up to the apes and men. The human brain seems to us to-day to be the
greatest marvel that plasm, or the "living substance," has produced in
the course of millions of years.

The remarkable progress which has been made in the last few decades
in the anatomic and histological investigation of the brain does not
yet, it is true, enable us to make a clear delimitation of the region
of the phronema and its relations to the neighboring sensory and
motor spheres in the cortex. We must, in fact, assume that there is
no sharp distinction in the lower stages of the vertebrate soul; in
the older and phylogenetically more distant stages they were not yet
differentiated. Even now there are still intermediaries between the
æsthetal and phronetal cells. But we may expect with confidence that
further progress in the comparative anatomy of the brain will, with
the aid of embryology, throw more and more light on these complicated
structures. In any case, the fundamental fact is now empirically
established that the phronema (the real organ of the soul) forms a
definite part of the cortex of the brain, and that without it there can
be no reason, no mental life, no thought, and no knowledge.

Since we regard psychology as a branch of physiology, and examine
the whole of the phenomena of mental life from the same monistic
stand-point as all other vital functions, it follows that we can make
no exception for knowledge and reason. In this we are diametrically
opposed to the current systems of psychology, which regard psychology,
not as a natural science, but as a mental science. In the next chapter
we shall see that this position is wholly unjustified. Unfortunately,
this dualistic attitude is shared by a number of distinguished modern
physiologists, who otherwise adopt the monistic principles; they
take the soul to be, in the Cartesian sense, a supernatural entity.
Descartes--a pupil of the Jesuits--only applied his theory to man,
and regarded animals as soulless automata. But the theory is quite
absurd in modern physiologists, who know from innumerable observations
and experiments that the brain, or psychic organ, in man behaves
just as it does in the other mammals, and especially the primates.
This paradoxical dualism of some of our modern physiologists may be
partly explained by the perverse theory of knowledge which the great
authority of Kant, Hegel, etc., has imposed on them; and partly by
a concern for the current belief in immortality, and the dread of
being decried as "materialists" if they abandon it. As I do not share
this belief, I examine and appreciate the physiological work of the
phroneta just as impartially as I deal with the organs of sense or the
muscles. I find that the one is just as much subject as the other to
the law of substance. Hence we must regard the chemical processes in
the ganglionic cells of the cortex as the real factors of knowledge and
all other psychic action. The chemistry of the neuroplasm determines
the vital function of the phronema. The same must be said of its most
perfect and enigmatic function, consciousness. Although this greatest
wonder of life is only directly accessible by the introspective method,
or by the mirroring of knowledge in knowledge, nevertheless the use of
the comparative method in psychology leads us to believe confidently
that the lofty self-consciousness of man differs only in degree, and
not in kind, from that of the ape, dog, horse, and other higher mammals.

Our monistic conception of the nature and seat of the soul is strongly
confirmed by psychiatry, or the science of mental disease. As an
old medical maxim runs, _Pathologia physiologiam illustrat_--the
science of disease throws light on the sound organism. This maxim is
especially applicable to mental diseases, for they can all be traced to
modifications of parts of the brain which discharge definite functions
in the normal state. The localization of the disease in a definite part
of the phronema diminishes or extinguishes the normal mental function
which is discharged by this section. Thus disease of the speech-centre,
in the third frontal convolution, destroys the power of speech; the
destruction of the visual region (in the occipital convolutions) does
away with the power of sight; the lesion of the temporal convolutions
destroys hearing. Nature herself here conducts delicate experiments
which the physiologist could only accomplish very imperfectly or not at
all. And although we have in this way only succeeded as yet in showing
the functional dependence of a certain part of the mental functions on
the respective parts of the cerebrum, no unprejudiced physician doubts
to-day that it is equally true of the other parts. Each special mental
activity is determined by the normal constitution of the relevant part
of the brain, a section of the phronema. Very striking examples of this
are afforded in the case of idiots and microcephali, the unfortunate
beings whose cerebrum is more or less stunted, and who have accordingly
to remain throughout life at a low stage of mental capacity. These
poor creatures would be in a very pitiable condition if they had a
clear consciousness of it, but that is not the case. They are like
vertebrates from which the cerebrum has been partly or wholly removed
in the laboratory. These may live for a long time, be artificially
fed, and execute automatic or reflex (and in part purposive) motions,
without our perceiving a trace of consciousness, reason, or other
mental function in them.

The embryology of the child-soul has been known in a general way for
thousands of years, and has been an object of keen interest to all
observant parents and teachers; but it was not until about twenty years
ago that a strictly scientific study was made of this remarkable and
important phenomenon. In 1884 Kussmaul published his _Untersuchungen
über das Seelenleben des neugeborenen Menschen_, and in 1882 W. Preyer
published his _Mind of the Child_ [English translation; Dr. J. Sully
has several works on the same subject]. From the careful manuals which
these and other observers have published, it is clear that the new-born
infant not only has no reason or consciousness, but is also deaf, and
only gradually develops its sense and thought-centres. It is only by
gradual contact with the outer world that these functions successively
appear, such as speech, laughing, etc.; later still come the power of
association, the forming of concepts and words, etc. Recent anatomic
observations quite accord with these physiological facts. Taken
together, they convince us that the phronema is undeveloped in the
new-born infant; and so we can no more speak in this case of a "seat of
the soul" than of a "human spirit" as a centre of thought, knowledge,
and consciousness. Hence the destruction of abnormal new-born
infants--as the Spartans practised it, for instance, in selecting the
bravest--cannot rationally be classed as "murder," as is done in even
modern legal works. We ought rather to look upon it as a practice of
advantage both to the infants destroyed and to the community. As the
whole course of embryology is, according to our biogenetic law, an
abbreviated repetition of the history of the race, we must say the same
of psychogenesis, or the development of the "soul" and its organ--the
phronema.

Comparative psychology comes next in importance to embryology as a
means of studying the ancestral history of the soul. Within the ranks
of the vertebrates we find to-day a long series of evolutionary stages
which reach up from the lowest acrania and cyclostoma to the fishes
and dipneusta, from these to the amphibia, and from these again to the
amniota. Among the latter, moreover, the various orders of reptiles and
birds on the one hand, and of mammals on the other, show us how the
higher psychic powers have been developed step by step from the lower.
To this physiological scale corresponds exactly the morphological
gradation revealed by the comparative anatomy of the brain. The most
interesting and important part of this is that which relates to the
highest developed class--the mammals; within this class we find the
same ever-advancing gradation. At its summit are the primates (man, the
apes, and the half-apes), then the carnivora, a part of the ungulates,
and the other placentals. A wide interval seems to separate these
intelligent mammals from the lower placentals, the marsupials and
monotremes. We do not find in the latter the high quantitative and
qualitative development of the phronema which we have in the former;
yet we find every intermediate stage between the two. The gradual
development of the cerebrum and its chief part--the phronema--took
place during the Tertiary period, the duration of which is estimated by
many recent geologists at from twelve to fifteen (at the least three to
five) million years.

As I have gone somewhat fully, in chapters vi.-ix. of the _Riddle_,
into the chief results of the modern study of the brain and its
radical importance for psychology and the theory of knowledge, I
need only refer the reader thereto. There is just one point I may
touch here, as it has been attacked with particular vehemence by my
critics. I had made several allusions to the works of the distinguished
English zoologist, Romanes, who had made a careful comparative study
of mental development in the animal and man, and had continued the
work of Darwin. Romanes partly retracted his monistic convictions
shortly before his death, and adopted mystic religious views. As
this conversion was only known at first through one of his friends,
a zealous English theologian [Dr. Gore], it was natural to retain a
certain reserve. However, it turned out that there had really been
in this case (just as in the case of the aged Baer) one of those
interesting psychological metamorphoses which I have described in
chapter vi. of the _Riddle_. Romanes suffered a good deal from illness
and grief at the loss of friends in his last years. In this condition
of extreme depression and melancholy he fell under mystic influences
which promised him rest and hope by belief in the supernatural. It
is hardly necessary to point out to impartial readers that such a
conversion as this does not shake his earlier monistic views. As in
similar cases where deep emotional disturbance, painful experiences,
and exuberant hope have clouded the judgment, we must still hold that
it is the place of the latter, and not of the emotions or of any
supernatural revelation, to attain a knowledge of the truth. But for
such attainment it is necessary for the organ of mind, the phronema, to
be in a normal condition.[3]

Of all the wonders of life, consciousness may be said to be the
greatest and most astounding. It is true that to-day most physiologists
are agreed that man's consciousness, like all his other mental powers,
is a function of the brain, and may be reduced to physical and chemical
processes in the cells of the cortex. Nevertheless, some biologists
still cling to the metaphysical view that this "central mystery of
psychology" is an insoluble enigma, and not a natural phenomenon.
In face of this, I must refer the reader to the monistic theory of
consciousness which I have given in chapter x. of the _Riddle_, and
must insist that in this case again embryology is the best guide
to a comprehension of the subject. Sight is next to consciousness,
in many respects, as one of the wonders of life. The well-known
embryology of the eye teaches us how sight--the perception of images
from the external world--has been gradually evolved from the simple
sensitiveness to light of the lower animals, by the development of a
transparent lens. In the same way the conscious soul, the internal
mirror of the mind's own action, has been produced as a new wonder of
life out of the unconscious associations in the phronema of our earlier
vertebrate ancestors.

From this thorough and unprejudiced appreciation of the biology of
the phronema it follows that the knowledge of truth, the aim of all
science, is a natural physiological process, and that it must have
its organs like all other psychic functions. These organs have been
revealed to us so fully in the advance of biology during the last
half-century that we may be said to have a generally satisfactory idea
of the natural character of their organization and action, though we
are still far from enjoying a complete anatomical and physiological
insight into their details. The most important acquisition we have
made is the conviction that all knowledge was originally acquired _a
posteriori_ and from experience, and that its first sources are the
impressions made on our organs of sense. Both these--the peripheral
sense-organs--and the phronema, or central psychic organ, are subject
to the law of substance; and the action of the phronema is just as
reducible to chemical and physical processes as the action of the
organs of sense.

In diametrical opposition to our monistic and empirical theory of
knowledge, the prevailing dualistic metaphysics assumes that our
knowledge is only partly empirical and _a posteriori_, and is partly
quite independent of experience and _a priori_, or due to the original
constitution of our "immaterial" mind. The powerful authority of Kant
has lent enormous prestige to this mystic and supernatural view, and
the academic philosophers of our time are endeavoring to maintain it.
A "return to Kant" is held to be the only means of salvation for
philosophy; in my opinion it should be a return to nature. As a fact,
the return to Kant and his famous theory of knowledge is an unfortunate
"crab-walk" on the part of philosophy. Our modern metaphysicians
regard the brain, as Kant did one hundred and twenty years ago, as a
mysterious, whitish-gray, pulpy mass, the significance of which as an
instrument of the mind is very enigmatic and obscure. But for modern
biology the brain is the most wonderful structure in nature, a compound
of innumerable soul-cells or neurona. These have a most elaborate
finer structure, are combined in a vast psychic apparatus by thousands
of interlacing nerve-fibrils, and are thus fitted to accomplish the
highest mental functions.

FIRST TABLE

ANTITHESIS OF THE TWO WAYS OF ATTAINING THE TRUTH

  MONISTIC THEORY OF KNOWLEDGE      │  DUALISTIC THEORY OF KNOWLEDGE
                                    │
  1. Knowledge is a natural process,│  1. Knowledge is a supernatural
  not a miracle.                    │  process, a miracle.
                                    │
  2. Knowledge, as a natural        │  2. Knowledge, as a transcendental
  process, is subject to the        │  process, is not subject
  general law of substance.         │  to the law of substance.
                                    │
  3. Knowledge is a physiological   │  3. Knowledge is not a physiological,
  process, with the brain for       │  but a purely spiritual,
  its anatomic organ.               │  process.
                                    │
  4. The part of the human brain    │  4. The part of the human brain
  in which knowledge is             │  which seems to act as
  exclusively engendered            │  organ of knowledge is
  is a definite and limited         │  really only the instrument
  part of the cortex, the           │  that allows the spiritual
  phronema.                         │  process to appear.
                                    │
  5. The organ of knowledge, or     │  5. The organ of knowledge, or
  the phronema, consists of         │  the phronema (the sum of
  the association-centres,          │  the association-centres),
  and differs by its special        │  is merely a part of the
  histological structure from       │  instrument of mind, like
  the neighboring sensory           │  the neighboring and correlated
  and motor centres in the          │  sensory and motor-centres.
  cortex, and it is in close        │
  relation with these.              │
                                    │
  6. The innumerable cells which    │  6. The innumerable phronetal
  make up the phronema--the         │  cells, as the microscopic
  phronetal cells--are              │  elementary parts of the
  the elementary organs of          │  phronema, are, it is true,
  the cognitive process: the        │  indispensable instruments
  possibility of knowledge          │  of the cognitive process,
  depends on their normal           │  but not its real factors--merely
  physical texture and chemical     │  finer parts of its
  composition.                      │  instrument.
                                    │
  7. The physical process of        │  7. The metaphysical process of
  knowledge consists in the         │  knowledge consists in the
  combination or association        │  combination or association
  of presentations, the             │  of presentations, which are
  first sources of which are        │  only partly traceable to
  the impressions transmitted       │  sense-impressions, and are
  to the sense-centres.             │  partly supersensual, transcendental
                                    │  processes.
                                    │
  8. Hence all knowledge originally │  8. Hence knowledge is of two
  comes from experience,            │  kinds: empirical and _a
  by means of the                   │  posteriori_ knowledge, obtained
  organs of sense; partly           │  by experience, and
  directly (direct experience,      │  transcendental _a priori_
  observation, and experiment       │  knowledge, independent of
  of the present),                  │  experience. Mathematics
  partly indirectly (historical     │  especially belongs to the
  and indirectly transmitted        │  latter class, its axioms
  past experiences).                │  differing from empirical
  All knowledge (even mathematical) │  truths by their absolute
  is of empirical                   │  certainty.
  origin and _a posteriori_.        │




II

LIFE

 Definition of life--Comparison with a flame--Organism and
 organization--Machine theory of life--Organisms without organs:
 monera--Organization and life of the chromacea--Stages of
 organization--Complex organisms--Symbolic organisms--Organic
 compounds--Organisms and inorganic bodies compared in regard
 to matter, form, and function--Crystalloid and colloid
 substances--Life of crystals--Growth of crystals--Waves of
 growth--Metabolism--Catalysis--Fermentation--Biogenesis--Vital
 force--Old and new vitalism--Palavitalism--Antivitalism--Neovitalism.


As the object of this work is the critical study of the wonders of
life, and a knowledge of the truth concerning them, we must first
of all form a clear idea of the meaning of "life" and "wonder," or
miracle. For thousands of years men have appreciated the difference
between life and death, between living and lifeless bodies; the former
are called organisms, and the latter known as inorganic bodies.
Biology--in the widest sense--is the name of the science which treats
of organisms; we might call the science which deals with the inorganic
"abiology," abiotik, or anorgik. The chief difference between the two
provinces is that organisms accomplish peculiar, periodically repeated,
and apparently spontaneous movements, which we do not find in inorganic
matter. Hence life may be conceived as a special process of movement.
Recent study has shown that this is always connected with a particular
chemical substance, _plasm_, and consists essentially in a circulation
of matter, or _metabolism_. At the same time modern science has shown
that the sharp distinction formerly drawn between the organic and the
inorganic cannot be sustained, but that the two kingdoms are profoundly
and inseparably united.

Of all the phenomena of inorganic nature with which the life-process
may be compared, none is so much like it externally and internally as
the flame. This important comparison was made two thousand four hundred
years ago by one of the greatest philosophers of the Ionic school,
Heraclitus of Ephesus--the same thinker who first broached the idea of
evolution in the two words, _Panta rei_--all things are in a state of
flux. Heraclitus shrewdly conceived life as a fire, a real process of
combustion, and so compared the organism to a torch.

Max Verworn has lately employed this metaphor with great effect in his
admirable work on general physiology, and has especially dealt with
the comparison of the individual life-form with the familiar butterfly
shape of the gas-flame. He says:

 The comparison of life to a flame is particularly suitable for
 helping us to realize the relation between form and metabolism. The
 butterfly-shape of a gas-flame has a very characteristic outline.
 At the base, immediately above the burner, there is still complete
 darkness; over this is a blue and faintly luminous zone; and over
 this again the bright flame expands on either side like the wings of
 a butterfly. This peculiar form of the flame, with its characteristic
 features, which are permanent, as long as we do not interfere with
 the gas or the environment, is solely due to the fact that the
 grouping of the molecules of the gas and the oxygen at various parts
 of the flame is constant, though the molecules themselves change
 every moment. At the base of the flame the molecules of the gas are
 so thickly pressed that the oxygen necessary for their combustion
 cannot penetrate; hence the darkness we find here. In the bluish
 zone a few molecules of oxygen have combined with the molecules of
 the gas: we have a faint light as the result. But in the body of
 the flame the molecules of the gas are so freely combined with the
 oxygen of the atmosphere that we have a lively combustion. However,
 the exchange of matter (metabolism) between the outpouring gas and
 the surrounding air is so regulated that we always find the same
 molecules in the same quantity at the same spot. Thus we get the
 permanent flame, with all its characteristics. But if we alter the
 circulation by lessening the stream of gas, the shape of the flame
 changes, because now the disposition of the molecules on both sides
 is different. Thus the study of the gas-jet gives us, even in detail,
 the features we find in the structure of the cell.

The scientific soundness of this metaphor is all the more notable as
the phrase, "the flame of life," has long been familiar both in poetry
and popular parlance.

In the sense in which science usually employs the word "organism,"
and in which we employ it here, it is equivalent to "living thing" or
"living body." The opposite to it, in the broad sense, is the anorganic
or inorganic body. Hence the word "organism" belongs to physiology,
and connotes essentially the visible life-activity of the body, its
metabolism, nutrition, and reproduction.

However, in most organisms we find, when we examine their structure
closely, that this consists of various parts, and that these parts
are put together for the evident purpose of accomplishing the vital
functions. We call them _organs_, and the manner in which they are
combined, apparently on a definite plan, is their _organization_. In
this respect, we compare the organism to a machine in which some one
has similarly combined a number of (lifeless) parts for a definite
purpose, but according to a preconceived and rationally initiated
design.

The familiar comparison of an organism to a machine has given rise to
very serious errors in regard to the former, and has, of late, been
made the base of false dualistic principles. The modern "machine-theory
of life" which is raised thereon demands an intelligent design and
a deliberate constructing engineer for the origin of the organism,
just as we find in the case of the machine. The organism is then very
freely compared to a watch or a locomotive. In order to secure the
regular working of such a complicated mechanism, it is necessary to
arrange for a perfect co-operation of all its parts, and the slightest
accident to a single wheel suffices to throw it out of gear. This
figure was particularly employed by Louis Agassiz (1858), who saw
"an incarnate thought of the Creator" in every species of animal and
plant. Of late years it has been much used by Reinke in the support of
his theosophic dualism. He described God, or "the world-soul," as the
"cosmic intelligence," but ascribes to this mystic immaterial being
the same attributes that the catechism and the preacher give to the
Creator of heaven and earth. He compares the human intelligence which
the watch-maker has put into the elaborate structure of the watch with
the "cosmic intelligence" which the Creator has put in the organism,
and insists that it is impossible to deduce its purposive organization
from its material constituents. In this he entirely overlooks the
immense difference between the "raw material" in the two cases. The
"organs" of the watch are metallic parts, which fulfil their purpose in
virtue only of their physical properties (hardness, elasticity, etc.).
The organs of the living organism, on the other hand, perform their
functions chiefly in virtue of their chemical composition. Their soft
plasma-body is a chemical laboratory, the highly elaborate molecular
structure of which is the historical product of countless complicated
processes of heredity and adaptation. This invisible and hypothetical
molecular structure must not (as is often done) be confused with the
real and microscopically discoverable structure of the plasm, which
is of great importance in the question of organization. If one is
disposed to assume for this molecular structure a simple chemical
substance, a deliberate design, and an "intelligent natural force"
for cause, one is bound to do the same for powder, and say that the
molecules of charcoal, sulphur, and saltpetre have been purposively
combined to produce an explosion. It is well known that powder was not
made according to a theory, but accidentally discovered in the course
of experiment. The whole of this favorite machine-theory of life, and
the far-reaching dualistic conclusions drawn from it, tumble to pieces
when we study the simplest organisms known to us, the monera; for these
are really organisms without organs--and without organization!

I endeavored in my _Generelle Morphologie_(1866) to draw the attention
of biologists to these simplest and lowest organisms which have no
visible organization or composition from different organs. I therefore
proposed to give them the general title of monera. The more I have
studied these structureless beings--cells without nuclei!--since that
time, the more I have felt their importance in solving the greatest
questions of biology--the problem of the origin of life, the nature
of life, and so on. Unfortunately, these primitive little beings are
ignored or neglected by most biologists to-day. O. Hertwig devotes
one page of his three-hundred-page book on cells and tissues to them;
he doubts the existence of cells without nuclei. Reinke, who has
himself shown the existence of unnucleated cells among the bacteria
(_beggiatoa_), does not say a word about their general significance.
Bütschli, who shares my monistic conception of life, and has given it
considerable support by his own thorough study of plasma-structures
and the artificial production of them in oil and soap-suds, believes,
like many other writers, that the "composition of even the simplest
elementary organism from cell-nucleus and protoplasm" (the primitive
organs of the cell) is indispensable. These and other writers suppose
that the nucleus has been overlooked in the protoplasm of the monera
I have described. This may be true for one section of them; but
they say nothing about the other section, in which the nucleus is
certainly lacking. To this class belong the remarkable _chromacea_
(_phycochromacea_ or _cyanophycea_), and especially the simplest
forms of these, the _chroococcacea_ (_chroococcus_, _aphanocapsa_,
_glœocapsa_, etc.). These plasmodomous (plasma-forming) monera,
which live at the very frontier of the organic and inorganic worlds,
are by no means uncommon or particularly difficult to find; on the
contrary, they are found everywhere, and are easy to observe. Yet they
are generally ignored because they do not square with the prevailing
dogma of the cell.

I ascribe this special significance to the chromacea among all
the monera I have instanced because I take them to be the oldest
phyletically, and the most primitive of all living organisms known
to us. In particular their very simple forms correspond exactly to
all the theoretic claims which monistic biology can make as to the
transition from the inorganic to the organic. Of the chroococcacea,
the chroococcus, glœocapsa, etc., are found throughout the world;
they form thin, usually bluish-green coats or jelly-like deposits on
damp rocks, stones, bark of trees, etc. When a small piece of this
jelly is examined carefully under a powerful microscope, nothing is
seen but thousands of tiny blue-green globules of plasma, distributed
irregularly in the common structureless mass. In some species we can
detect a thin structureless membrane enclosing the homogeneous particle
of plasm; its origin can be explained on purely physical principles
by "superficial energy"--like the firmer surface-layer of a drop of
rain, or of a globule of oil swimming in water. Other species secrete
homogeneous jelly-like envelopes--a purely chemical process. In some
of the chromacea the blue-green coloring matter (_phyocyan_) is stored
in the surface-layer of the particle of plasm, while the inner part
is colorless--a sort of "central body." However, the latter is by no
means a real, chemically and morphologically distinct, nucleus. Such a
thing is completely lacking. The whole life of these simple, motionless
globules of plasm is confined to their metabolism (or _plasmodomism_,
chapter x.) and the resulting growth. When the latter passes a certain
stage, the homogeneous globule splits into two halves (like a drop
of quicksilver when it falls). This simplest form of reproduction is
shared by the chromacea (and the cognate bacteria) with the chromatella
or chromatophora, the green particles of chlorophyll inside ordinary
plant-cells; but these are only parts of a cell. Hence no unprejudiced
observer can compare these unnucleated and independent granules of
plasm with real (nucleated) cells, but must conceive them rather
as _cytodes_. These anatomic and physiological facts may easily be
observed in the chromacea, which are found everywhere. The organism
of the simplest chromacea is really nothing more than a structureless
globular particle of plasm; we cannot discover in them any composition
of different organs (or organella) for definite vital functions. Such a
composition or organization would have no meaning in this case, since
the sole vital purpose of these plasma-particles is self-maintenance.
This is attained in the simplest fashion for the individual by
metabolism; for the species it is effected by self-cleavage, the
simplest conceivable form of reproduction.

Modern histologists have discovered a very intricate and delicate
structure in many of the higher unicellular protists and in many
of the tissue-cells of the higher animals and plants (such as the
nerve-cells). They wrongly conclude that this is universal. In my
opinion, this complication of the structure of the elementary organism
is always a secondary phenomenon, the slow and gradual result of
countless phylogenetic processes of differentiation, initiated by
adaptation and transmitted to posterity by heredity. The earliest
ancestors of all these elaborate nucleated cells were at first simple,
unnucleated cytodes, such as we find to-day in the ubiquitous monera.
We shall see more about them in the ninth and fifteenth chapters.

Naturally, this lack of a visible histological structure in the
plasma-globule of the monera does not exclude the possession of an
invisible molecular structure. On the contrary, we are bound to assume
that there is such a structure, as in all albuminoid compounds, and
especially all plasmic bodies. But we also find this elaborate chemical
structure in many lifeless bodies; some of these, in fact, show a
metabolism similar to that of the simplest organisms. We will return
subsequently to this subject of catalysis. Briefly, the only difference
between the simplest chromacea and inorganic bodies that have catalysis
is in the special form of their metabolism, which we call plasmodomism
(formation of plasm), or "carbon-assimilation." The mere fact that the
chromacea assume a globular form is no sign whatever of a morphological
vital process; drops of quicksilver and other inorganic fluids take the
same shape when the individual body is formed under certain conditions.
When a drop of oil falls into a fluid of the same specific gravity with
which it cannot mix (such as a mixture of water and spirits of wine),
it immediately assumes a globular shape. Inorganic solids usually
take the form of crystals instead. Hence the distinctive feature of
the simplest organism, the plasma-particles of the monera, is neither
anatomic structure nor a certain shape, but solely the physiological
function of plasmodomism--a process of chemical synthesis.

The difference between the monera I have described and any higher
organism is, I think, greater in every respect than the difference
between the organic monera and the inorganic crystals. Nay, even the
difference between the unnucleated monera (as cytodes) and the real
nucleated cells may fairly be regarded as greater still. Even in the
simplest real cell we find the distinction between two different
organella, or "cell-organs," the internal nucleus and the outer
cell-body. The _caryoplasm_ of the nucleus discharges the functions
of reproduction and heredity; the _cytoplasm_ of the cell-body
accomplishes the metabolism, nutrition, and adaptation. Here we have,
therefore, the first, oldest, and most important process of division
of labor in the elementary organism. In the unicellular protists the
organization rises in proportion to the differentiation of the various
parts of the cell; in the tissue-forming histona it rises again in
proportion to the distribution of work (or ergonomy) among the various
organs. Darwin has given us in his theory of selection a mechanical
explanation of the apparent design and purposiveness in this.

In order to have a correct monistic conception of organization, it
is important to distinguish the individuality of the organism in its
various stages of composition. We shall treat this important question,
about which there is a good deal of obscurity and contradiction, in a
special chapter (vii.). It suffices for the moment to point out that
the unicellular beings (protists) are simple organisms both in regard
to morphology and physiology. On the other hand, this is only true in
the physiological sense of the histona, the tissue-forming animals
and plants. From the morphological point of view they are made up of
innumerable cells, which form the various tissues. These histonal
individuals are called sprouts in the plant world and persons in the
animal world. At a still higher stage of organization we have the
trunk or stem (cormus), which is made up of a number of sprouts or
persons, like the tree or the coral-stem. In the fixed animal stems the
associated individuals have a direct bodily connection, and take their
food in common; but in the social aggregations of the higher animals
it is the ideal link of common interest that unites the individuals,
as in swarms of bees, colonies of ants, herds of mammals, etc. These
communities are sometimes called "animal-states." Like human polities,
they are organisms of a higher type.

However, in order to avoid misunderstanding, we must take the word
"organism" in the sense in which most biologists use it--namely, to
designate an individual living thing, the material substratum of which
is plasm or "living substance"--a nitrogenous carbon-compound in a
semi-fluid condition. It leads to a good deal of misunderstanding
when separate functions are called organisms, as is done sometimes
in speaking of the soul or of speech. It would be just as correct to
call seeing or running an organism. It is advisable also in scientific
treatises to refrain from calling inorganic compounds as such
"organisms," as, for instance, the sea or the whole earth. Such names,
having a purely symbolical value, may very well be used in poetry. The
rhythmic wave-movement of the ocean may be regarded as its respiration,
the surge as its voice, and so on. Many scientists (like Fechner)
conceive the whole earth with all its organic and inorganic contents
as a gigantic organism, whose countless organs have been arranged
in an orderly whole by the world-reason (God). In the same way the
physiologist, Preyer, regards the glowing heavenly bodies as "gigantic
organisms, whose breath is, perhaps, the glowing vapor of iron, whose
blood is liquid metal, and whose food may be meteorites." The danger of
this poetic application of the metaphorical sense of organism is very
well seen in this instance, as Preyer builds on it a quite untenable
hypothesis of the origin of life (see chapter xv.).

In the wider sense the word "organic" has long been used in chemistry
as an antithesis to inorganic. By organic chemistry is generally
understood the chemistry of the compounds of carbon, that element being
distinguished from all the others (some seventy-eight in number) by
very important properties. It has, in the first place, the property of
entering into an immense variety of combinations with other elements,
and especially of uniting with oxygen, hydrogen, nitrogen, and sulphur
to form the most complicated albuminoids (see the _Riddle_, chapter
xiv.). Carbon is a biogenetic element of the first importance, as I
explained in my carbon-theory in 1866. It might even be called "the
creator of the organic world." At first these organogenetic compounds
do not appear in the organism in organized form--that is to say, they
are not yet distributed into organs with definite purposes. Such
organization is a result, not the cause, of the life-process.

I have already shown in the fourteenth chapter of the _Riddle_(and at
greater length in the fifteenth chapter of my _History of Creation_)
that the belief in the essential unity of nature, or the monism of
the cosmos, is of the greatest importance for our whole system. I
gave a very thorough justification of this cosmic monism in 1866. In
the fifth chapter of the _Generelle Morphologie_ I considered the
relation of the organic to the inorganic in every respect, pointing
out the differences between them on the one hand, and their points of
agreement in matter, form, and force on the other. Nägeli some time
afterwards declared similarly for the unity of nature in his able
_Mechanisch-physiologische Begründung_ _der Abstammungslehre_(1884).
Wilhelm Ostwald has recently done the same, from the monistic point of
view of his system of energy, in his _Naturphilosophie_, especially in
the sixteenth chapter. Without being acquainted with my earlier work,
he has impartially compared the physico-chemical processes in the
organic and inorganic worlds, partly adducing the same illustrations
from the instructive field of crystallization. He came to the same
monistic conclusions that I reached thirty-six years ago. As most
biologists continue to ignore them, and as, especially, modern vitalism
thrusts these inconvenient facts out of sight, I will give a brief
summary once more of the chief points as regards the matter, form, and
forces of bodies.

Chemical analysis shows that there are no elements present in organisms
that are not found in inorganic bodies. The number of elements that
cannot be further analyzed is now put at seventy-eight; but of these
only the five organogenetic elements already mentioned which combine
to form plasm--carbon, oxygen, hydrogen, nitrogen, and sulphur--are
found invariably in living things. With these are generally (but not
always) associated five other elements--phosphor, potassium, calcium,
magnesium, and iron. Other elements may also be found in organisms; but
there is not a single biological element that is not also found in the
inorganic world. Hence the distinctive features which separate the one
from the other can be sought only in some special form of combination
of the elements. And it is carbon especially, the chief organic
element, that by its peculiar affinity enters into the most diverse and
complicated combinations with other elements, and produces the most
important of all substances, the albuminoids, at the head of which is
the living plasm (_cf._ chapter vi.).

An indispensable condition of the circulation of matter (metabolism)
which we call life is the physical process of osmosis, which is
connected with the variations in the quantity of water in the living
substance and its power of diffusion. The plasm, which is of a spongy
or viscous consistency, can take in dissolved matter from without
(endosmosis) and eject matter from within (exosmosis). This absorptive
property (or "imbibition-energy") of the plasm is connected with the
colloidal character of the albuminoids. As Graham has shown, we may
divide all soluble substances into two groups in respect of their
diosmosis--crystalloids and colloids. Crystalloids (such as soluble
salt and sugar) pass more easily into water through a porous wall
than colloids (such as albumen, glue, gum, caramel). Hence we can
easily separate by dialysis two bodies of different groups which are
mixed in a solution. For this we need a flat bottle with side walls
of india-rubber and bottom of parchment. If we let this vessel float
in a large one containing plenty of water, and pour a mixture of
dissolved gum and sugar into the inner vessel, after a time nearly
all the sugar passes through the parchment into the water, and an
almost pure solution of gum remains in the bottle. This process of
diffusion, or osmosis, plays a most important part in the life of all
organisms; but it is by no means peculiar to the living substance,
any more than the absorptive or viscous condition is. We may even
have one and the same substance--either organic or inorganic--in both
conditions, as crystal or as colloid. Albumen, which usually seems
to be colloidal, forms hexagonal crystals in many plant-cells (for
instance, in the aleuron-granules of the endosperm), and tetrahedric
hœmoglobin-crystals in many animal-cells (as in the blood corpuscles
of mammals). These albuminoid crystals are distinguished by their
capacity for absorbing a considerable quantity of water without losing
their shape. On the other hand, mineral silicon, which appears as
quartz in an immense variety (more than one hundred and sixty) of
crystalline forms, is capable in certain circumstances (as metasilicon)
of becoming colloidal and forming jelly-like masses of glue. This
fact is the more interesting because silicium behaves in other ways
very like carbon, is quadrivalent like it, and forms very similar
combinations. Amorphous (or non-crystalline) silicium (a brown powder)
stands in relation to the black metallic silicon-crystals just as
amorphous carbon does to graphite-crystals. There are other substances
that may be either crystalloid or colloid in different circumstances.
Hence, however important colloidal structure may be for the plasm and
its metabolism, it can by no means be advanced as a distinctive feature
of living matter.

Nor is it possible to assign an absolute distinction between the
organic and the inorganic in respect of morphology any more than of
chemistry. The instructive monera once more form a connecting bridge
between the two realms. This is true both of the internal structure
and the outward form of both classes of bodies--of their individuality
(chapter vii.) and their type (chapter viii.). Inorganic crystals
correspond morphologically to the simplest (unnucleated) forms of the
organic cells. It is true that the great majority of organisms seem to
be conspicuously different from inorganic bodies by the mere fact that
they are made up of many different parts which they use as organs for
definite purposes of life. But in the case of the monera there is no
such organization. In the simplest cases (chromacea, bacteria) they are
structureless, globular, discoid, or rod-shaped plasmic individuals,
which accomplish their peculiar vital function (simple growth and
subdivision) solely by means of their chemical constitution, or their
invisible molecular structure.

The comparison of cells with crystals was made in 1838 by the founders
of the cell-theory, Schleiden and Schwann. It has been much criticised
by recent cytologists, and does not hold in all respects. Still it is
of importance, as the crystal is the most perfect form of inorganic
individuality, has a definite internal structure and outward form,
and obtains these by a regular growth. The external form of crystals
is prismatic, and bounded by straight surfaces which cut each other
at certain angles. But the same form is seen in the skeletons of many
of the protists, especially the flinty shells of the diatomes and
radiolaria; their silicious coverings lend themselves to mathematical
determination just as well as the inorganic crystals. Midway between
the organic plasma-products and inorganic crystals we have the
_bio-crystals_, which are formed by the united plastic action of the
plasm and the mineral matter--for instance, the crystalline flint and
chalk skeletons of many of the sponges, corals, etc. Further, by the
orderly association of a number of crystals we get compound crystal
groups, which may be compared to the communities of protists--for
instance, the branching ice-flowers and ice-trees on the frozen
window. To this regular external form of the crystal corresponds a
definite internal structure which shows itself in their cleavage, their
stratified build, their polar axes, etc.

If we do not restrict the term "life" to organisms properly so-called,
and take it only as a function of plasm, we may speak in a broader
sense of the life of crystals. This is seen especially in their
growth, the phenomenon which Baer regarded as the chief character of
all individual development. When a crystal is formed in a matrix,
this is done by attracting homogeneous particles. When two different
substances, A and B, are dissolved in a mixed and saturated solution,
and a crystal of A is put in the mixture, only A is crystallized out of
it, not B; on the other hand, if a crystal of B is put in, A remains in
solution and B alone assumes the solid crystalline form. We may, in
a certain sense, call this choice _assimilation_. In many crystals we
can detect internally an interaction of their parts. When we cut off
an angle in a forming crystal, the opposite angle is only imperfectly
formed. A more important difference between the growth of crystals and
monera is that the former only grow by _apposition_, or the deposit of
fresh solid matter at their surface; while the monera grow, like all
cells, by _intussusception_, or the taking of new matter into their
interior. But this difference is easily explained by their difference
in consistency, the crystal being solid and the plasm semi-fluid.
Moreover, the difference is not absolute; there are intermediary
stages between apposition and intussusception. A colloid globule
suspended in a salt solution in which it is not dissolved may grow by
intussusception.

It was once the custom to restrict sensation and movement to animals,
but they are now recognized to be present in nearly all living matter.
They are, in fact, not altogether lacking in crystals, as the molecules
move in crystallization in definite directions, and unite according to
fixed laws; they must, therefore, also possess sensation, as we could
not otherwise understand the attraction of the homogeneous particles.
We find in crystallization, as in every chemical process, certain
movements which are unintelligible without sensation--unconscious
sensation, of course. In this respect, also, then, the growth of all
bodies follows the same laws (_cf._ chapters xiii. and xv.).

The growth of a crystal is restricted like the growth of a moneron or
of any cell. If the limit is passed and the conditions remain favorable
to growth, we find an instance of that excessive or _transgressive_
growth which we call reproduction in the case of living individuals.
But we find just the same kind of extension in the inorganic crystal.
Every crystal grows in a supersaturated medium only up to a definite
size, which is determined by its chemical-molecular constitution. When
this limit is reached a number of small crystals appear on the large
one. Ostwald, who has made a thorough comparison of the process of
growth in crystals and monera, especially notices the striking analogy
between a bacterium (a plasmophagous moneron) growing and multiplying
in its nutritive fluid and a crystal in its matrix. When the water
slowly evaporates from a supersaturated solution of Glauber-salt, not
only does a crystal slowly grow in it, but several young crystals
appear on it. The analogy with the bacterium multiplying in its
nutritive fluid can even be followed as far as its permanent forms or
"spores." This quiescent form is assumed by the bacterium if its supply
of food is exhausted; if fresh food is added, the multiplication by
cleavage begins again. In the same way the crystals of Glauber-salt
begin to decay when the solution is evaporated; they lose their crystal
water, but not their power of multiplication. Even the amorphous powder
of the salt causes again the formation of new watery crystals when put
in a supersaturated solution. But the powder loses this property when
it is heated, just as the dormant forms (or spores) of the bacteria
lose their power of germination.

The exhaustive comparison of the growth of crystals and monera (as the
simplest forms of unnucleated cells) is important, because it shows
the possibility of tracing the vital function of reproduction--which
had usually been regarded as a quite special "wonder of life"--to
purely physical conditions. The division of the growing individual
into several young ones must necessarily take place when the natural
limit of growth has been passed, and when the chemical composition of
the growing body and the cohesion of its molecules allow no further
enlargement by the assumption of new matter. In order to illustrate
the limit of this transgressive growth by a simple physical example,
Ostwald imagines a ball placed in a small flat basin, built up high on
one side. The ball is in a state of equilibrium in the basin; when it
is lightly pushed aside it always returns to its original position.
But when the push goes beyond a certain point, and the ball is thrust
over the side of the basin, the balance is lost; the ball does not
return, but falls to the ground. The crystal behaves just in the same
way in a supersaturated solution when it exercises its power of forming
new crystals; and it is just the same with the bacterium growing in a
nutritive fluid when it passes the limit of its volume of growth, and
divides into two individuals.

As we can find no morphological and little physiological difference
between the living and non-living, we must look upon metabolism as
the chief characteristic of organic life. This process causes the
conversion of food into plasm; it is determined by the vital force
itself, and is the formation of new living matter. It thus effects
the nutrition and growth of the living being, and therefore its
reproduction, which is merely transgressive growth. As I shall describe
this metabolism fully in the tenth chapter, I will do no more here
than emphasize the fact that this vital process also has analogies in
inorganic chemistry, in the curious process of catalysis, especially
that form of it which we call fermentation.

The distinguished chemist Berzelius discovered in 1810 the
remarkable fact that certain bodies, by their mere presence, apart
from their chemical affinity, set other bodies in decomposition or
composition without being themselves affected. Thus, for instance,
sulphuric acid changes the starch in sugar without undergoing any
alteration itself. Finely ground platinum brought in contact with
hydrogen-superoxide divides it into hydrogen and oxygen. Berzelius
called this process _catalysis_; Mitscherlich, who discovered the
cause of it to be the peculiar surface-action of many bodies, gave
it the name of "contact-action." It was afterwards discovered that
catalysis of this kind is very general, and that a special form of
it--fermentation--plays an important part in the life of organisms.

This special form of contact-action which we call fermentation is
always effected by catalytic bodies of the albuminoid class, and,
in fact, of the group of non-coagulable proteins which are known as
peptones. They have--in however small a quantity--the capacity to
throw into decomposition large masses of organic matter (in the form
of yeast, putrid matter, etc.) without themselves taking part in the
decomposition. When these ferments are free and unorganized they
are called enzyma, in opposition to organized ferments (bacteria,
yeast-fungi, etc.); though the catalytic action of the latter
also consists essentially in the production of enzyma. The recent
investigations of Verworn, Hofmeister, Ostwald, etc., have shown that
these catalyses play everywhere an important part in the life of the
plasm. Many recent chemists and physiologists are of opinion that
plasm is a _colloid catalysator_, and that all the varied activities
of life are connected with this fundamental vital chemistry. Thus
Franz Hofmeister (1901) says in his excellent work on _The Chemical
Organization of the Cell_:

 The belief that the agents of the chemical transformation in the
 cell are catalysators of a colloid nature is in complete accord
 with other facts that have been directly ascertained. What else are
 the chemists' ferments but colloid catalysators? The idea that the
 ferments are the essential chemical agency in the cell is calculated
 to meet the difficulty which arises from the smallness of the cell
 in appreciating its chemical processes. However large we suppose the
 colloid ferment molecules to be, there is room for millions of them
 in the smallest cell.

In the same way Ostwald attributes the greatest significance to
catalysis in connection with the vital processes, and seeks to explain
them on his theory of energy by reference to the duration of chemical
processes. In the discourse "On Catalysis" that he delivered at Hamburg
in 1901 he says:

 We must recognize the enzyma as catalysators that arise in the
 organism during the life of the cells, and by their action relieve
 the living being of the greater part of its duties. Not only are
 digestion and assimilation controlled by enzyma from first to last,
 but the fundamental vital action of most organisms, the production
 of the necessary chemical energy by combustion at the expense of
 the oxygen in the air, takes place with the explicit co-operation
 of enzyma, and would be impossible without them. Free oxygen is, as
 is well known, a very inert body at the temperature of the living
 body, and the maintenance of life would be impossible without some
 acceleration of its rate of reaction.

In his further observations on catalysis and metabolism he says that
they are both equally subject to the physico-chemical laws of energy.

Max Verworn has given us a very searching analysis of the molecular
process in the catalytic aspect of metabolism in his _Biogen
Hypothesis_ (1903), "a critical and experimental study of the processes
in living matter." He simplifies the catalytic theory of the enzyma
by tracing all the phenomena of life to the catalytic metabolism
of one single chemical compound, the plasm, and regards its active
molecules, the biogens, as the ultimate chemical factors of the vital
process. While the enzyma hypothesis assumes that there are in each
cell a great number of different enzyma which are all co-ordinated,
and each of which only performs its little special work, the biogen
hypothesis deduces all the vital phenomena from one compound, the
biogenetic plasm; and thus the biogen molecules, which increase by
division into parts, are the sole factors of biological catalysis.
Verworn also points out the analogy between this enzymatic process of
metabolism and the inorganic processes of catalysis--for instance,
in the manufacture of English sulphuric acid. A small and constant
quantity of nitromuriatic acid, with the aid of air and water, converts
an unlimited mass of sulphuretted acid into sulphuric acid without
being changed itself; the molecule of the nitromuriatic acid breaks
up steadily by the giving-off of oxygen, and is then restored by the
assumption of oxygen.

The manifold and changeful phenomena of life and their sudden
extinction at death seem to every thoughtful man to be something
so wonderful and so different from all the changes in inorganic
nature that from the very beginning of biological philosophy special
forces were assumed to explain it. This was particularly due to
the remarkable, orderly structure of the organism and the apparent
purposiveness of the vital processes. Hence, in earlier days a
special organic force (_archæus insitus_) was assumed, controlling
the individual life and pressing the "raw forces" of inorganic matter
into its service. In the same way a special formative impulse was
supposed to preside over the wonderful processes of development. When
physiology began to win its independence, about the middle of the
eighteenth century, it explained the peculiar features of organic life
by a specific vital force. The idea was generally received, and Louis
Dumas endeavored thoroughly to establish it at the beginning of the
nineteenth century (_cf._ chapter iii. of the _Riddle_).

As the theory of a vital force, or vitalism, plays an important part
in the study of the wonders of life, has undergone the most curious
modifications in the course of the nineteenth century, and has been
lately revived with great force, we must give a short account of it
in its various forms. The phrase can be interpreted in a monistic
sense, if we understand by it the sum of the forms of energy which
are especially distinctive of the organism, particularly metabolism
and heredity. In this we pass no opinion on their nature, and do
not say that they are specifically different from the forces of
inorganic nature. We might call this monistic conception "physical
vitalism." However, the usual metaphysical vitalism affirms in a
thoroughly dualistic sense that the vital force is a teleological and
super-mechanical principle, is essentially different from the ordinary
forces of nature, and of a transcendental character. The special form
in which this theory of a supernatural vital force has been presented
for the last twenty years is often called Neovitalism; we might call
the older form, by contrast, Palavitalism.

The older idea of the vital force as a special energy could very well
be accepted in the first third of the nineteenth century, and in the
eighteenth, because the physiology of the time was destitute of the
most important aids to the founding of a mechanical theory. There was
then no such thing as the cell-theory or as physiological chemistry;
ontogeny and paleontology were still in their cradles. Lamarck's
theory of descent (1809) had been done to death, like his fundamental
principle: "Life is only an elaborate physical phenomenon." Hence we
can easily understand how physiologists acquiesced in the vitalist
hypothesis up to 1833, and supposed the wonders of life to be enigmatic
phenomena that escaped physical explanation.

But the position of Palavitalism changed in the second third of the
nineteenth century. In 1833 appeared Johannes Müller's classical
_Manual of Human Physiology_, in which the great biologist not only
made a comparative study of the vital phenomena in man and the animals,
but sought to provide a sound basis for it in all its sections by his
own observations and experiments. It is true that Müller retained
to the last (1858) the current idea of a vital force, as the supreme
regulator of all the vital activities. However, he did not regard it
as a metaphysical principle (like Haller, Kant, and their followers),
but as a natural force, subject, like all others, to fixed chemical
and physical laws, and subordinate to the whole. In his comprehensive
study of every single vital function--the organs of sense and the
nervous system, metabolism and the action of the heart, speech and
reproduction--Müller endeavored above all to establish, by close
observation of the facts and careful experiments, the regularity
of the phenomena, and to explain their development by a comparison
of the higher and lower forms. Hence Johannes Müller is wrongly
described--as he has been of late--as a vitalist; he was rather the
first physiologist to provide a physical foundation for the current
metaphysical vitalism. He really gives an indirect proof of the reverse
theory, as E. Dubois-Reymond rightly observed in his brilliant memorial
speech. In the same way Schleiden (1843) cut the ground from under
vitalism in botany. By his cell-theory (1838) he showed the unity of
the multicellular organism to be the resultant of the functions of all
the cells which compose it.

The physical explanation of the vital processes and the rejection
of Palavitalism were general in the last third of the nineteenth
century. This was due most of all to the great advance in experimental
physiology, which Carl Ludwig and Felix Bernard led as regards the
animal body, and Julius Sachs and Wilhelm Preyer for the plant. While
these and other physiologists used the remarkable results of modern
physics and chemistry in the experimental study of the vital functions,
and sought to determine their complicated course in terms of mass and
weight and formulate their discoveries as mathematically as possible,
they brought a great number of the wonders of life under the same
fixed laws that were recognized in the physics and chemistry of the
inorganic world. On the other hand, vitalism met with a powerful
opponent in Charles Darwin, who solved, by his theory of selection,
one of the most obscure biological problems, the constantly repeated
question: How can we give a mechanical explanation of the orderly
structures of the living being? How was this ingenious machine of the
animal or plant body unconsciously produced by natural means, without
supposing that some intelligent artificer or creator had deliberately
designed and produced it?

The further development of Darwin's theory of selection in the last
four decades, and the increasing support which has been given to
the theory of descent in the great advance of ontogeny, phylogeny,
comparative anatomy, and physiology, did much to establish the monistic
conception of life. It took the shape more and more of a definite
anti-vitalism. Hence it is strange to find that in the course of the
last twenty years the old vitalism that everybody had thought dead has
lifted up its head once more, though in a new and modified form.[4]
This modern vitalism comprises two essentially different tendencies.

The partisans of the modern vital force are divided into two groups,
which may be designated the sceptical and the dogmatic. Sceptical
Neovitalism was first formulated by Bunge, of Basle (1887), in the
introduction to his _Manual of Physiological Chemistry_. While he
granted the possibility of a full explanation of one part of the vital
phenomena by mechanical causes, or the physical and chemical forces
of lifeless nature, he rejected it for the other half, especially for
psychic activities. He insists that the latter cannot be explained
mechanically, and that there is nothing analogous to them in inorganic
nature; only a supra-mechanical vital force can produce them, and this
is transcendental and beyond the range of scientific inquiry. Much the
same was said later by Rindfleisch (1888), more recently by Richard
Neumeister in his _Studies of the Nature of Vital Phenomena_ (1903),
and by Oscar Hertwig in the lecture on "The Development of Biology in
the Nineteenth Century," which he delivered at Aachen in 1900.

This sceptical Neovitalism is far surpassed by the dogmatic system,
the chief actual representatives of which are the botanist Johannes
Reinke and the metaphysician Hans Driesch. The vitalist writings of the
latter, which are devoid of any grasp of historical development, have
gained a certain vogue through the extraordinary arrogance of their
author and the obscurity of his mystic and contradictory speculations.
Reinke, on the other hand, has presented his transcendental dualism
in clever and attractive form in two works which deserve notice on
account of their consistent dualism. In the first of these, _The World
as Reality_ (1899), Reinke gives us "the outline of a scientific theory
of the universe." The second work (1901) has the title, _Introduction
to Theoretical Biology_. The two works have the same relation to each
other as my _Riddle of the Universe_ and the present supplementary
volume. As our philosophic convictions are diametrically opposed in the
main issues, and as we both think ourselves consistent in developing
them, the comparison of them is not without interest in the great
struggle of beliefs. Reinke is an avowed supporter of dualism, theism,
and teleology. He reduces all the phenomena of life to a supernatural
miracle.

SECOND TABLE

ANTITHESIS OF THE MONISTIC AND DUALISTIC THEORIES OF ORGANIC LIFE

  MONISTIC THEORY OF LIFE            │      DUALISTIC THEORY OF LIFE
  (Biophysics)                       │ (Vitalism)
                                     │
  1. The phenomena of life are       │ 1. The phenomena of life are
  merely functions of plasm,         │ wholly or partly independent
  determined by the physical,        │ of the plasm, and
  chemical, and morphological        │ determined by a special
  character of the                   │ immaterial force, the vital
  living matter.                     │ force (_vis vitalis_).
                                     │
  2. The energy of the plasm (as     │ 2. The energy of the plasm is
  the sum-total of the forces        │ wholly or partly subject
  which are connected with           │ to the immaterial vital
  the living matter) is subject      │ force, which controls and
  to the general laws of             │ directs the physical and
  physics and chemistry.             │ chemical forces of the
                                     │ living matter.
                                     │
  3. The obvious regularity of the   │ 3. The general regularity in the
  vital processes and the            │ organization and in the
  organization they produce          │ vital processes it accomplishes
  are the outcome of natural         │ is the outcome of
  evolution; their physiological     │ conscious creation; it can
  factors (heredity                  │ only be explained by intelligent
  and adaptation) are subject        │ immaterial forces
  to the law of substance.           │ which are not subject to
                                     │ the law of substance.
                                     │
  4. All the various functions       │ 4. All the various functions of
  have thus been mechanically        │ organisms have been produced
  produced, orderly                  │ by design, the
  structures having been             │ historical evolution (or
  created by adaptation and          │ phyletic transformation)
  transmitted to posterity           │ being directed to a preconceived
  by heredity.                       │ ideal end.
                                     │
  5. Nutrition is a physico-chemical │ 5. Nutrition is an inexplicable
  process, the metabolism            │ miracle of life, and cannot
  of which has an                    │ be understood by chemical
  analogy in inorganic catalysis.    │ and physical processes.
                                     │
  6. Reproduction is a mechanical    │ 6. Reproduction is an inexplicable
  consequence of transgressive       │ miracle of life,
  growth, analogous                  │ without any analogy in
  to the elective multiplication     │ inorganic nature.
  of crystals.                       │
                                     │
  7. The movement of organisms       │ 7. The movement of organisms
  is, in every form, not             │ is an inexplicable metaphysical
  essentially different from         │ miracle of life,
  the movements of inorganic         │ specifically different from
  dynamos.                           │ all inorganic movements.
                                     │
  8. Sensation is a general form     │ 8. The sensation of organisms
  of the energy of substance,        │ can only be explained by
  not specifically different         │ ascribing a soul to them,
  in sensitive organisms and         │ an immaterial, immortal
  irritable inorganic objects        │ being that only dwells for
  (such as powder, dynamite).        │ a time in the body. After
  There is no such                   │ death this spirit lives an
  thing as an immaterial             │ independent life.
  soul.                              │




III

MIRACLES

 Miracle and natural law--Belief in miracles of savages (fetichism),
 of semi-civilized (idolatry), of civilized (theism), and of
 educated people (dualism)--Religious belief in miracles--Apostles'
 Creed--Article relating to creation--Article relating to
 redemption--Article relating to immortality--Philosophic belief in
 miracles--Academic thinkers and Free-thinkers--Dualism of Plato
 and Kant--Belief in miracles in the nineteenth century, in modern
 metaphysics, theology, and politics.


In ordinary parlance the word "miracle" means a number of different
things. We say a phenomenon is miraculous or wonderful[5] when we
cannot explain it and trace its causes. But we say a natural object
or a work of art is wonderful when it is unusually beautiful and
imposing--when it passes the ordinary limits of our experience. In this
work I do not take the word in this relative sense, but in the absolute
sense in which a phenomenon is said to transcend the limits of natural
law and lie beyond the range of rational explanation. In this sense
it means the same as "supernatural" or "transcendental." We can know
natural phenomena by our reason and bring them within our cognizance.
The miraculous can only be accepted on faith.

The belief in supernatural miracles is in contradiction to pure reason,
which lays the foundations of all science. Kant, who won so great a
vogue for the term "pure reason," understood by this originally "reason
as independent of experience." The phrase was used in a narrower sense
subsequently to express independence of dogma and prejudice, as the
base of pure and unprejudiced science. In this sense we oppose pure
reason to superstition.

I have dealt in the sixteenth chapter of the _Riddle_ with the
important question of the relations of knowledge and faith. But I
must return to the subject here, as what I said has given rise to a
good deal of misunderstanding and criticism. I by no means claimed,
as my opponents allege, to "know everything," or to have solved every
problem. In fact, I said repeatedly that there are narrow limits to
our knowledge, and always will be. I had also expressly stated that
the irresistible impulse to learn in the intelligent man, or reason's
constant demand to know causes, presses us to fill up the gaps in our
knowledge by faith. But I had at the same time pointed out the contrast
between scientific (natural) and religious (supernatural) faith. The
one leads us to form hypotheses and theories; the other ends in myths
and superstition. Scientific faith fills the gaps in our knowledge
of natural law with temporary hypotheses; but mystic religious faith
contradicts natural law, and transcends its limits in the form of a
belief in miracles.

The great triumph of the progress of science in the nineteenth century,
its theoretical value in the formation of a rational philosophy
of life, and its practical value on the various sides of modern
civilization, consist, above all, in the absolute recognition of fixed
natural laws. That relation of things to each other, which we call
causation, makes it possible for us to understand and explain facts.
We feel that our thirst for a knowledge of the causes of things is
contented when science points out the "sufficient reason" of them. In
the whole province of inorganic cosmology natural law is now generally
recognized to be all-powerful; in astronomy, geology, physics,
and chemistry all phenomena are reduced to fixed laws, and in the
long-run to the all-embracing law of substance, the great law of the
conservation of matter and force (_Riddle_, chapter xii.).

It is otherwise in biology, or the organic section of cosmology. Here
we still find miracles set up in opposition to the law of substance,
and the transgression of natural laws by supernatural forces. The
belief in miracles of this kind, which pure reason calls superstition,
is still very wide-spread--much more prevalent than is usually thought.
For my part, I hold that superstition and unreason are the worst
enemies of the human race, while science and reason are its greatest
friends. Hence it is our duty and task to attack the belief in miracles
wherever we find it, in the interest of the race. We have to prove that
the reign of natural law extends over the whole world of phenomena
as far as we can reach it. A general survey of the history of faith
on the one hand and of science on the other clearly shows that the
advance of the latter has always been accompanied by an increasing
knowledge of fixed natural laws and the shrinking of superstition
into an ever-lessening area. To-day we convince ourselves of this
by an impartial examination of mental culture at the various stages
of civilization. For this purpose I take the four chief stages of
mental development which Fritz Schultze has given in his _Physiology
of Uncivilized Races_, and Alexander Sutherland in his work, _On the
Origin and Growth of the Moral Instinct_: 1, savages; 2, barbarians; 3,
civilized races; 4, educated races (_cf._ chapter i.).

The mental life of savages rises little above that of the higher
mammals, especially the apes, with which they are genealogically
connected. Their whole interest is restricted to the physiological
functions of nutrition and reproduction, or the satisfaction of hunger
and thirst in the crudest animal fashion. Without fixed habitation,
constantly struggling for existence, they live on the raw produce of
nature--fruits, the roots of wild plants, and the animals they fish
in the water or catch on land. Their intelligence moves within the
narrowest bounds, and one can no more (or no less) speak of their
reason than of that of the more intelligent animals. Of art and science
there is no question. Their impulse to discover causes is satisfied
with the simplest association of phenomena which have a merely external
connection, but no intimate relation to each other. Thus arises
their _fetichism_, that irrational trust in fetiches which Fritz
Schultze has traced to four distinct causes: their false estimate of
the value of an object, their anthropomorphic conception of nature,
the imperfect association of their ideas, and the strength of their
emotions, especially hope and fear. Any favorite object, a stone or
a bone, may work miracles as a fetich and exercise all kinds of good
or evil influence, and is therefore honored, feared, and worshipped.
At first the worship was paid to the invisible spirit that dwelt in
the particular object; but it was often transferred afterwards to the
dead object itself. Among the different savage races the belief in
fetiches presents a number of stages, corresponding to the beginnings
of reason. The lowest stage is found in the lowest races, such as the
Veddahs of Ceylon, the Andaman Islanders, Bushmen, and Akkas (of New
Guinea). A somewhat higher stage is met in the middle races (Australian
negroes, Tasmanians, Hottentots, and Tierra del Fuegians); and a still
higher intellectual development is shown by the next group (most of
the Indians of North and South America, the aboriginal inhabitants
of India, etc.). Modern comparative ethnography and evolution and
prehistoric and anthropological research have shown us that our own
ancestors, ten thousand and more years ago, were (like the prehistoric
ancestors of all races of men) savages, and that their earliest belief
in miracles was a crude fetichism.

By barbarians we understand the races that are found between savage
and civilized peoples. They show the first beginnings of civilization,
and are superior to savages chiefly in the possession of agriculture
and the keeping of cattle. They make a provident use of the productive
forces of organic nature, artificially produce large quantities of
food, and are thus enabled by the abundance of food to turn their minds
to other interests. We find that they have the rudiments of art and
science. Their religion does not at first rise much above fetichism,
but soon reaches the stage of animism, lifeless objects in nature
being credited with souls. Worship is no longer paid to favorite dead
objects (stones, bones, etc.), but generally to living things, trees
and animals, and especially to images of gods which have the form
of animals or men, and are believed to possess souls. As demons or
spirits, these have a great influence on the fortunes of men. At first
this soul is conceived to be purely material; it disappears at the
death of the body and lives apart. As the breathing and the beat of the
pulse and heart cease when a man dies, the seat of the soul is thought
to be the lungs, heart, or some other part of the body. The idea of the
immortality of the soul takes on innumerable forms among them, like the
belief in the miracles which are worked by the gods, demons, spirits,
etc. Evolution again points out a long gradation of forms of faith, if
we compare the lower, middle, and higher races.

Civilized races are distinguished from barbaric by the formation of
states with an extensive division of labor. The social organism is
not only larger and more powerful, but is capable of a greater variety
of achievements, the functions of the various states and classes of
workers being more highly differentiated and mutually complementary
(like the cells and tissues in the higher animal body of the metazoa).
Nutrition is easier and more luxurious. Art and science are well
developed. A great advance is seen in regard to religion, the numerous
gods being generally conceived as manlike spirits, and finally
subordinated to a chief god. The belief in miracles flourishes greatly
in poetry; in philosophy it is more and more restricted. In the end,
the working of miracles is limited monotheistically to one god, or to
his priests and other men to whom he communicates the power.

Modern civilization in the narrower sense, as a contrast to the
older civilization, opens, in my opinion, at the beginning of the
sixteenth century. At that time took place some of the greatest
achievements of human thought among civilized peoples, and these
broke the chains of tradition and gave a fresh impetus to progress.
Men's own mental outlook was widened by the system of Copernicus
and the Reformation freed them from the yoke of the papacy. Shortly
before, the discovery of the New World and the circumnavigation of
the globe had convinced men of the rotundity of the earth; geography,
natural history, medicine, and other sciences gained inspiration and
independence; printing and engraving provided an important means of
spreading the new knowledge. This fresh impetus was chiefly of service
to philosophy, which now more and more rejected the dictation of the
Church and superstition; though it was far from casting off the fetters
altogether. This was not generally possible until the nineteenth
century, when empirical science assumed an enormous importance, and in
the ensuing period of speculation the physical conception of the world
gained more and more on the metaphysical. Pure knowledge, thus grounded
on science, entered into sharper conflict than ever with religious
faith. If, as in the preceding cases, we distinguish three stages in
the development of modern civilization, we recognize the progressive
liberation from superstition by scientific knowledge.

When we compare the higher forms of religion of civilized nations we
find the same emotional cravings and thought-processes constantly
recurring, and the belief in miracles developing in much the same
way. The three founders of the great monotheistic Mediterranean
religion--Moses, Christ, and Mohammed--were equally regarded as
wonder-working prophets, having direct intercourse with God in virtue
of their special gifts, and transmitting his commands to men in the
shape of laws. The extraordinary authority they enjoy, which has
given so much prestige to the religions they founded, is grounded for
ordinary people on their miraculous powers--the healing of the sick,
the raising of the dead, the expulsion of devils, and so on. If we
examine the miracles of Christ as they are given in the gospels, they
run counter to the laws of nature and rational explanation just in
the same way as the similar miracles of Buddha and Brahma in Hindoo
mythology, or of Mohammed in the Koran. The same must be said of the
belief in the miracle of the bread and wine in the Lord's supper,
and the like. The Creed which was probably drawn up by the leaders
of the Christian communities of the second century, and received its
final and present form in the Church of South Gaul in the fourth
and fifth centuries, has been obligatory for Christians for fifteen
hundred years, and recognized by both Church and State as compulsory.
This Apostles' Creed was also recognized in Luther's catechism to
be fundamental, and is taught in all Protestant and Roman Catholic
schools (though not in the Greek Catholic) as the foundation of
religious instruction. This extraordinary prestige of the Apostles'
Creed, and its great influence on the education of the young, no less
than its glaring inconsistency with rational knowledge, compel us to
devote a few pages to a critical examination of its three articles.

The first article of the Creed deals with creation, and runs: "I
believe in God, the Father Almighty, Creator of heaven and earth."
The modern science of evolution has shown that there never was any
such creation, but that the universe is eternal and the law of
substance all-ruling. God himself is anthropomorphically conceived as
an "Almighty Creator" and the Father of man; heaven (in the sense of
the geocentric system) is imagined as a great blue vault spanning the
earth. The notion of this "personal God" as an intelligent, immaterial
being, creating the material world out of nothing, is wholly irrational
and meaningless. That Luther accepted this childish and scientifically
worthless idea is clear from his commentary on the first article--"What
is that?"

The second article of the Creed deals with the dogma of salvation
in the following words: "I believe in Jesus Christ, his only son,
our Lord, who was conceived of the Holy Ghost, born of the Virgin
Mary, suffered under Pontius Pilate, was crucified, dead, and buried,
descended into hell, on the third day rose again from the dead,
ascended into heaven, sitteth at the right hand of God, the Father
Almighty, whence he will come to judge the living and the dead." As
these dogmas of the second article contain the chief points of the
redemption theory, and are still treasured by millions of educated
people, it is necessary to point out their flagrant opposition to pure
reason. The chief evil of such creeds is that children, who are yet
incapable of reflecting, are forced to learn them by heart. They then
remain unchallenged as revealed truths.

The myth of the conception and birth of Jesus Christ is mere fiction,
and is at the same stage of superstition as a hundred other myths of
other religions. Of the three persons who are mysteriously blended
in the triune God, the son Christ is supposed to be begotten by both
Father and Holy Ghost, parthenogenetically through the Virgin Mary. I
have dealt with the physiology of parthenogenesis in the seventeenth
chapter of the _Riddle_. The curious adventures of Christ after his
death, the descent into hell, resurrection, and ascension, are also
fantastic myths due to the narrow geocentric ideas of an uneducated
people. Troelslund has admirably explained the strong influence they
have had in his interesting book, _The Idea of Heaven and of the
World_.[6] The idea of the "last judgment," with Christ sitting on the
right hand of the Father, as many famous mediæval pictures represent
(notably Michael Angelo's in the Sistine Chapel at the Vatican), is
another outcome of a thoroughly childish and anthropomorphic attitude.

It is remarkable that this second article of the Creed says nothing
about "redemption," which forms its heading [in Germany]. Luther has
dealt with it in his commentary. Christ is believed to have suffered a
painful death, like many thousand other martyrs, for his conviction of
the truth of his faith and teaching--which reminds one of the more than
a hundred thousand men who were done to death by the Inquisition and in
the religious wars of the Middle Ages; but not one of the millions of
ministers who preach on it every Sunday seems to have shown a rational
causal connection of this death with the alleged redemption from sin
and death. The whole of this story of redemption has sprung from the
primitive, obscure, ethical ideas of uneducated races, especially the
crude belief in the propitiatory power of human sacrifice. It has
no practical moral value except for those who believe in personal
immortality--a scientifically untenable dogma. Whoever builds on this
empty promise of a better life beyond may soothe himself with this
hope, and reconcile himself to the thousand ills and defects of this
world. But the man who studies this life as it really is will not
find that the belief in redemption has brought any real improvement.
Want and misery and sin are as prevalent as ever; indeed, our modern
civilization has, in many respects, increased them.

The third and last article of the Apostles' Creed runs: "I believe
in the Holy Ghost, the holy Catholic Church, the communion of
saints, the forgiveness of sins, the resurrection of the body, and
life everlasting." In the curious commentary that Luther made on
this article in his catechism, he said that "man cannot believe
of his own reason in Jesus Christ"--which is very true--but the
Holy Ghost must lead him thereto with his grace; but how the third
person of the Trinity effects this enlightenment and sanctification
he did not explain. What is meant by the "communion of saints" and
the "holy Catholic Church" must be gathered in the light of their
history--especially the history of Romanism. This most powerful and
still influential section of the Christian Church, which especially
claims the title of Catholic and "the one ark of salvation," is really
a most pitiful caricature of pure primitive Christianity. It has, with
consummate skill, succeeded in preaching the beneficent teaching of
Christ in theory and doing just the opposite in practice; we need only
recall the Inquisition, the dark history of the Middle Ages, and the
political hierarchy which still dominates so much of civilization.

However, by far the most important clause in the third article is
the final expression of belief in "the resurrection of the body and
life everlasting." That this greatest "wonder of life" was originally
conceived in a purely material form is evident from thousands of
pictures in which famous painters have realistically depicted the
resurrection of the dead, the aërial flight of the happy souls of the
blessed, and the torments of the damned in hell. It is thus conceived
still by the majority of believers who take eternal life to be an
"enlarged and improved edition" of life here below. This is equally
true of Christian and Mohammedan pictures and of the athanatist ideas
that prevailed in other religions long before Christ was born, even
of the first rudiments of the belief in primitive races. As long as
the geocentric theory prevailed, and the heavens were thought to be a
sort of blue glass bell, illumined by thousands of little stars and
the lamp of the sun, arching like a vault over the flat earth, and
the fires of hell burned in the cellars below, this barbaric notion
of a resurrection of the body and a last judgment could easily be
maintained. But its roots were destroyed when Copernicus refuted the
geocentric theory in 1545; and athanatism became quite untenable when
Darwin shattered the dogma of anthropocentricism. Not only the crude
older materialistic idea of eternal life, but also the refined new
spiritualistic version, has been rendered untenable by the progress of
science in the nineteenth century. I have shown this in the eleventh
chapter of the _Riddle_, which closes with the words: "If we take a
comprehensive glance at all that modern anthropology, psychology,
and cosmology teach with regard to athanatism, we are forced to this
definite conclusion. The belief in the immortality of the human soul
is in hopeless contradiction with the most solid empirical truths of
modern science."[7]

The great influence which has been exercised on civilized nations
by the Christian beliefs, supported by the practical exigencies of
the state, for thousands of years, was chiefly seen in the crude
superstition of the mass of the people. Confessions of faith became
as much a matter of routine as the latest fashion in dress or the
latest custom, etc. But even the majority of the philosophers were
more or less subordinated to the influence. It is true that a few
great thinkers freed themselves by the use of pure reason at an early
date from the prevalent superstition, and framed systems apart from
tradition and the priests. But most philosophers could not rise to
the altitude of these brave Free-thinkers; they remained "school-men"
in the literal sense, dependent on the dictation of authority, the
traditions of the school, and the dogmas of the Church. Philosophy
was the "handmaid" of theology and ecclesiasticism. If we examine the
history of philosophy in this light, we find in it a struggle for
twenty-five hundred years between two great tendencies--the dualism of
the majority (with theological and mystic leanings) and the monism of
the minority (with rationalistic and naturalistic disposition).

Especially notable are those great Free-thinkers of classic antiquity
who taught a monistic view of life in the sixth century before
Christ--the Ionic natural philosophers, Thales, Anaximander, and
Anaximenes; and a little later, Heraclitus, Empedocles, and Democritus.
They made the first thorough attempt to explain the world on rational
principles, independently of all mythological tradition and theological
dogmas. However, these remarkable efforts to found a primitive monism,
which found so finished an expression in the _De rerum natura_ of the
great poet-philosopher, Lucretius Carus (98-54 B.C.), were shortly
thrust out by the spread--through Plato's curious dualism--of the
belief in the immortality of the soul and the transcendental world of
ideas.

The Eleatics, Parmenides and Zeno, had foreshadowed in the fifth
century the division of philosophy into two branches; but Plato and
his pupil Aristotle (in the fourth century B.C.) succeeded in gaining
general acceptance for this dualism and antithesis of physics and
metaphysics. Physics devoted itself on the ground of experience to
the study of the phenomena of things, leaving their real essences (or
noumena) that lay behind the phenomena to metaphysics. These inner
essences are transcendental and inaccessible to empirical research;
they form the metaphysical world of eternal ideas, which is independent
of the real world, and has its highest unity in God, as the Absolute.
The soul, an eternal idea that dwells for a time in the passing human
body, is immortal. This consistent dualism of Plato's system, with
its sharp antithesis of this world and the next, of body and soul, of
world and God, is its chief characteristic. It became all the more
influential when Plato's pupil Aristotle blended it with his empirical
metaphysics, based on ample scientific experience, and pointed out the
idea in the entelechy, or purposively acting principle, of every being;
and especially when Christianity (three hundred years afterwards) found
in this dualism a welcome philosophic support of its own transcendental
tendency.

In the course of the thousand years which historians call the Middle
Ages, and which are usually dated from the fall of the Roman Empire
(476) to the discovery of America (1492), the superstition of civilized
races reached its highest development. The authority of Aristotle was
paramount in philosophy; it was used by the dominant Church for its
own purposes. But the influence of the Christian faith, with all the
gay coloring which the fairy-tales of the Bible added to its structure
of dogmas, was seen much more in practical life. In the foreground of
belief were the three central dogmas of metaphysics, to which Plato had
first given complete expression--the personal God as creator of the
world, the immortality of the soul, and the freedom of the human will.
As Christianity laid the greatest theoretical stress on the first two
dogmas and the greatest practical stress on the third, metaphysical
dualism soon prevailed on all sides. Especially inimical to scientific
inquiry was the Christian contempt of nature and its belittlement
of earthly life in view of the eternal life to come. As long as the
light of philosophical criticism in any form was extinguished, the
flower-garden of religious poetry flourished exceedingly and the idea
of miracle was taken as self-evident. We know what the practical result
of this superstition was from the ghastly history of the Middle Ages,
with its Inquisition, religious wars, instruments of torture, and
drowning of witches. In the face of the current enthusiasm for the
romantic side of mediævalism, the Crusades and Church art, we cannot
lay too much stress on these dark and bloody pages of its chronicles.

An impartial study of the immense progress made by science in the
course of the nineteenth century shows convincingly that the three
central metaphysical dogmas established by Plato have become untenable
for pure reason. Our clear modern insight into the regularity and
causative character of natural processes, and especially our knowledge
of the universal reign of the law of substance, are inconsistent with
belief in a personal God, the immortality of the soul, and the freedom
of the will. If we find this threefold superstition still widely
prevalent, and even retained by academic philosophers as an unshakable
consequence of "critical philosophy," we must trace this remarkable
fact chiefly to the great prestige of Immanuel Kant. His so-called
critical system--really a hybrid product of the crossing of pure reason
with practical superstition--has enjoyed a greater popularity than any
other philosophy, and we must stop to consider it for a moment.

I have described in chapters xiv. and xx. of the _Riddle_ the profound
opposition between my monistic system and Kant's dualistic philosophy.
In the appendix to the popular edition, especially, I have pointed out
the glaring contradictions of his system, which other philosophers
have often detected and criticised. Whenever there is question of his
teaching one must ask: "Which Kant do you mean? Kant I., the founder of
the monistic cosmogony, the critical formulator of pure reason; or Kant
II., the author of the dualistic criticism of judgment, the dogmatic
discoverer of practical reason?" These contradictions are partly due
to the psychological metamorphoses which Kant underwent (_Riddle_,
chapter vi.), partly to the perennial conflict between his scientific
bias towards a mechanical explanation of this world and his religious
craving (an outcome of heredity and education) and mystic belief in a
life beyond. This culminates in the distinction between the world of
sense and the world of spirit. The sense world (_mundus sensibilis_)
lies open to our senses and our intellect, and is empirically knowable
within certain limits. But behind it there is the spiritual world
(_mundus intelligibilis_) of which we know, and can know, nothing;
its existence (as the thing in itself) is, however, assured by our
emotional needs. In this transcendental world dwells the power of
mysticism.

It is said to be the chief merit of Kant's system that he first
clearly stated the problem: "How is knowledge possible?" In trying to
solve this problem introspectively, by a subtle analysis of his own
mental activity, he reached the conviction that the most important
and soundest of all knowledge--namely, mathematical--consists of
synthetic _a priori_ judgments, and that pure science is only possible
on condition that there are strict _a priori_ ideas, independent of
all experience, without _a posteriori_ judgments. Kant regarded this
highest faculty of the human mind as innate, and made no inquiry into
its development, its physiological mechanism, and its anatomic organ,
the brain. Seeing the very imperfect knowledge which human anatomy
had of the complicated structure of the brain at the beginning of the
nineteenth century, it was impossible to have at that time a correct
idea of its physiological function.

What seems to us to-day to be an innate capacity, or an _a priori_
quality, of our phronema, is really a phylogenetic result of a long
series of brain-adaptations, formed by _a posteriori_ sense-perceptions
and experiences.

Kant's much-lauded critical theory of knowledge is therefore just as
dogmatic as his idea of "the thing in itself," the unintelligible
entity that lurks behind the phenomena. This dogma is erroneously built
on the correct idea that our knowledge, obtained through the senses, is
imperfect; it extends only so far as the specific energy of the senses
and the structure of the phronema admit. But it by no means follows
that it is a mere illusion, and least of all that the external world
exists only in our ideas. All sound men believe, when they use their
senses of touch and space, that the stone they feel fills a certain
part of space, and this space does really exist. When all men who can
see agree that the sun rises and sets every day, this proves a relative
motion of the two heavenly bodies, and so the real existence of time.
Space and time are not merely necessary forms of intuition for human
knowledge, but real features of things, existing quite independently of
perception.

The increasing recognition of fixed natural laws which accompanied the
growth of science in the nineteenth century was bound to restrict more
and more the blind faith in miracles. There are three chief reasons
why we find this, nevertheless, still so prevalent--the continued
influence of dualistic metaphysics, the authority of the Christian
Church, and the pressure of the modern state in allying itself with
the Church. These three strong bulwarks of superstition are so hostile
to pure reason and the truth it seeks that we must devote special
attention to them. It is a question of the highest interests of
humanity. The struggle against superstition and ignorance is a fight
for civilization. Our modern civilization will only emerge from it in
triumph, and we shall only eliminate the last barbaric features from
our social and political life, when the light of true knowledge has
driven out the belief in miracles and the prejudices of dualism.

The remarkable history of philosophy in the nineteenth century, which
has not yet been written with complete impartiality and knowledge,
shows us in the first place an ever-increasing struggle between the
rising young sciences and the paramount authority of tradition and
dogma. In the first half of the century the various branches of biology
made progress without coming into direct collision with natural
philosophy. The great advance of comparative anatomy, physiology,
embryology, paleontology, the cell-theory, and classification,
provided scientists with such ample material that they attached
little importance to speculative metaphysics. It was otherwise in the
second half of the nineteenth century. Soon after its commencement
the controversy about the immortality of the soul broke out, in
which Moleschott (1852), Büchner, and Carl Vogt (1854) contended for
the physiological dependence of the soul on the brain, while Rudolph
Wagner endeavored to maintain the prevailing metaphysical idea of its
supernatural character. Then Darwin especially initiated in 1859 that
vast reform in biology which brought to light the natural origin of
species and shattered the miracle of creation. When the application
of the theory of descent and the biogenetic law to man was made by
anthropogeny (1874), and his evolution from a series of other mammals
was proved, the belief in the immortality of the soul, the freedom
of the will, and an anthropomorphic deity lost its last support.
Nevertheless, these three fundamental dogmas continued to find favor
in academic philosophy, which mostly followed the paths opened out by
Kant. Most of the representatives of philosophy at the universities
are narrow metaphysicians and idealists, who think more of the fiction
of the "intelligible world" than of the truth of the world of sense.
They ignore the vast progress made by modern biology, especially in
the science of evolution; and they endeavor to meet the difficulties
which it creates for their transcendental idealism by a sort of verbal
gymnastic and sophistry. Behind all these metaphysical struggles there
is still the personal element--the desire to save one's immortality
from the wreck. In this it comes into line with the prevailing
theology, which again builds on Kant. The pitiful condition of modern
psychology is a characteristic result of this state of things. While
the empirical physiology and pathology of the brain have made the
greatest discoveries, the comparative anatomy and histology of the
brain have thrown light on the details of its elaborate structure, and
the ontogeny and phylogeny of the brain have proved its natural origin,
the speculative philosophy of the schools stands aside from it all,
and in its introspective analysis of the functions of the brain will
not hear a word about the brain itself. It would explain the working
of a most complicated machine without paying any attention to its
structure. It is, therefore, not surprising to find that the dualistic
theories established by Kant flourish at our universities as they did
in the Middle Ages.

If the official philosophers, whose formal duty it is to study truth
and natural law, still cling to the belief in miracles in spite of
all the advance of empirical science, we shall not be surprised to
find this in the case of official theology. Nevertheless, the sense of
truth has prompted many unprejudiced and honorable theologians to look
critically at the venerable structure of dogma, and open their minds
to the streaming light of modern science. In the first third of the
nineteenth century a rationalistic section of the Protestant Church
attempted to rid itself of the fetters of dogma and reconcile its
ideas with pure reason. Its chief leader, Schleiermacher, of Berlin,
though an admirer of Plato and his dualist metaphysics, approached
very close to modern pantheism. Subsequent rationalistic theologians,
especially those of the Tübingen school (Baur, Zeller, etc.), devoted
themselves to the historical study of the gospels and their sources and
development, and thus more and more destroyed the base of Christian
superstition. Finally, the radical criticism of David Friedrich
Strauss showed, in his _Life of Jesus_ (1835), the mythological
character of the whole Christian system. In his famous work, _The Old
and New Faith_ (1872), this honorable and gifted theologian finally
abandoned the belief in miracles, and turned to natural knowledge and
the monistic philosophy for the construction of a rational view of
life on the basis of critical experience. This work has lately been
continued by Albert Kalthoff. Moreover, many modern theologians (such
as Savage, Nippold, Pfleiderer, and other liberal Protestants) have
endeavored in various ways to obtain a certain recognition for the
claims of progressive science, and reconcile them with theology, while
discarding the belief in the miraculous. However, these rationalistic
efforts, based on monistic or pantheistic views, are still isolated and
apparently without effect. The great majority of modern theologians
adhere to the traditional teaching of the Church, whose columns and
windows are still everywhere adorned with miracles. While a few liberal
Protestants restrict their faith to the three fundamental dogmas, most
of them still believe in the myths and legends which fill the pages of
the gospels. This orthodoxy is, moreover, encouraged of late by the
conservative and reactionary attitude taken up by many governments on
political grounds.

Most modern governments maintain the connection with the Church in the
idea that the traditional belief in the miraculous is the best security
for their own continuance. Throne and altar must protect and support
each other. However, this conservative-Christian policy meets two
obstacles in an increasing measure. On the one hand, the ecclesiastical
hierarchy is always trying to set its spiritual power above the secular
and make the state serve its own purposes; and, on the other hand, the
modern right of popular representation affords an opportunity to make
the voice of reason heard and oppose the reactionary conservatives
with opportune reforms. The chief rulers and the ministers of public
instruction, who have a great influence in this struggle, generally
favor the teaching of the Church, not out of conviction of its truth,
but because they think knowledge brings unrest, and because docile and
ignorant subjects are easier to rule than educated and independent
citizens. Hence it is that we now hear so much on every occasion, in
speeches from the throne and at banquets, at the opening of churches
and the unveiling of monuments, from able and influential speakers, of
the value of faith. They would give the palm to faith in its struggle
with knowledge. Thus we get this paradoxical situation in educated
countries (such as Prussia), that encouragement is given at once to
modern science and technical training and to the orthodox Church,
which is its deadly enemy. As a rule, it is not stated in these florid
orations to how many and what kind of miracles this precious faith must
extend. Nevertheless, we may yet, in view of the spread of intellectual
reaction in Germany, see it made obligatory for at least all priests,
teachers, and other servants of the state to profess a belief in the
three fundamental mysteries--the triune God of the catechism, the
personal immortality of the soul, and the absolute freedom of the human
will--and even in many of the other miracles which are found in the
gospels, sacred legends, and religious journals of our time.

The refined belief in the miraculous embodied in Kant's practical
philosophy assumed many different forms among his followers, the
Neo-Kantians, approaching sometimes more and sometimes less to the
conventional beliefs. Through a long series of variations, which still
continue to develop, it is gradually passing into the cruder form of
superstition which we find popular to-day as spiritism, and which
provides the basis for what is called occultism. Kant himself, in
spite of his subtle and clear critical faculty, had a decided leaning
to mysticism and positive dogmatism, which showed itself especially
in his later years. He thought a good deal of Swedenborg's idea of
the spirit world forming a universe apart, and compared this to his
_mundus intelligibilis_. Among the natural philosophers of the first
half of the nineteenth century, Schelling (in his later writings),
Schubert (in his _History of the Soul_ and _Observations on the Dark
Side of Science_), and Perty (in his mystic anthropology) especially
investigated the mysterious phenomena of mental action, and sought
to connect them with the physiological functions of the brain on the
one hand and supernatural spiritual agencies on the other. Modern
spook-seeking has no more value than mediæval magic, cabalism,
astrology, necromancy, dream-interpretation, and invocation of the
devil.

We must put at the same stage of superstition the spiritism and
occultism we find mentioned so much in modern literature. There are
always thousands of credulous folk in educated countries who are
taken in by the performances of the spiritists and their media, and
are ready to believe the unbelievable. Spirit-rapping, table-turning,
spirit-writing, the materialization and photographing of deceased
souls, find credit, not only among the uneducated masses, but even
among the most cultured, and sometimes among imaginative scientists.
It has been proved without avail by numbers of impartial observations
and experiments that these occultist performances depend partly on
conscious fraud and partly on careless self-deception. _Mundus vult
decipi_--"the world wishes to be taken in"--as the old saying has it.
This spiritistic fraud is particularly dangerous when it clothes itself
with the mantle of science, makes use of the physiological phenomena
of hypnotism, and even assumes a monistic character. Thus, for
instance, one of the best-known occultist writers, Karl du Prel, has
written, not only a _Philosophy of Mysticism and Studies of Scientific
Subjects_, but also (1888) a _Monistic Psychology_, which is dualistic
from beginning to end. In these popular writings lively imagination
and brilliant presentation are combined with a most flagrant lack of
critical sense and of knowledge of the elements of biology (_cf._
chapter xvi. of the _Riddle_). It seems that the hereditary bias
towards mysticism and superstition is not yet eliminated even from
the educated mind of our time. It is to be explained phylogenetically
by inheritance from prehistoric barbarians and savages, in whom
the earliest religious ideas were wholly dominated by animism and
fetichism.




IV

THE SCIENCE OF LIFE

 Object of biology--Relation to the other sciences--General
 and special biology--Natural philosophy--Monism:
 hylozoism, materialism, dynamism--Naturalism--Nature and
 spirit--Physics--Metaphysics--Dualism--Freedom and natural law--God
 in biology--Realism--Idealism--Branches of biology--Morphology and
 physiology--Anatomy and biogeny--Ergology and perilogy.


The broad realm of science has been vastly extended in the course of
the nineteenth century. Many new branches have established themselves
independently; many new and most fruitful methods of research have
been discovered, and have been applied with the greatest practical
success in furthering the advance of modern thought. But this enormous
expansion of the field of knowledge has its disadvantages. The
extensive division of labor it has involved has led to the growth
of a narrow specialism in many small sections; and in this way the
natural connection of the various provinces of knowledge, and their
relation to the comprehensive whole, have been partly or wholly lost
sight of. The importation of new terms which are used in different
senses by one-sided workers in the various fields of science has caused
a good deal of misunderstanding and confusion. The vast structure
of science tends more and more to become a tower of Babel, in the
labyrinthic passages of which few are at their ease and few any longer
understand the language of other workers. In these circumstances, it
seems advisable, at the commencement of our philosophic study of "the
wonders of life," to form a clear idea of our task. We must carefully
define the place of biology among the sciences, and the relation of
its various branches to each other and to the different systems of
philosophy.

In the broadest sense in which we can take it, biology is the whole
study of organisms or living beings. Hence not only botany (the science
of plants) and zoology (the science of animals), but also anthropology
(the science of man), fall within its domain. We then contrast with it
all the sciences which deal with inorganic or lifeless bodies, which
we may collectively call abiology (or anorganology); to this belong
astronomy, geology, mineralogy, hydrology, etc. This division of the
two great branches of science does not seem difficult in view of the
fact that the idea of life is sharply defined physiologically by its
metabolism and chemically by its plasm; but when we come to study the
question of abiogenesis (chapter xv.) we shall find that this division
is not absolute, and that organic life has been evolved from inorganic
nature. Moreover, biology and abiology are connected branches of
cosmology, or the science of the world.

While the idea of biology is now usually taken in this broad sense in
most scientific works and made to embrace the whole of living nature,
we often find (especially in Germany) a narrower application of the
term. Many authors (mostly physiologists) understand by it a section of
physiology--namely, the science of the relations of living organisms to
the external world, their habitat, customs, enemies, parasites, etc.
I proposed long ago to call this special part of biology œcology
(the science of home-relations), or bionomy. Twenty years later others
suggested the name of ethology. To call this special study any longer
biology in the narrower sense is very undesirable, because it is the
only name we have for the totality of the organic sciences.

Like every other science, biology has a general and a special part.
General biology contains general information about living nature;
this is the subject of the present study of the wonders of life. We
might also describe it as biological philosophy, since the aim of true
philosophy must be the comprehensive survey and rational interpretation
of all the general results of scientific research. The innumerable
discoveries of detailed facts which observation and experiment give
us, and which are combined into a general view of life in philosophy,
form the subject of empirical science. As the latter, on the side of
the organic world, or as empirical biology, forms the first object of
the science of life, and seeks to effect in the system of nature a
logical arrangement and summary grouping of the countless special forms
of life, this special biology is often wrongly called the science of
classification.

The first comprehensive attempt to reduce to order and unity the
ample biological material which systematic research had accumulated
in the eighteenth century was made by what we call "the older natural
philosophy" at the beginning of the nineteenth century. Reinhold
Treviranus (of Bremen) had made a suggestive effort to accomplish this
difficult task on monistic principles in his _Biology, or Philosophy of
Living Nature_ (1802). Special importance attaches to the year 1809, in
which Jean Lamarck (of Paris) published his _Philosophie Zoologique_,
and Lorentz Oken (of Jena) his _Manual of Natural Philosophy_. I have
fully appreciated the service of Lamarck, the founder of the theory
of descent, in my earlier writings. I have also recognized the great
merit of Lorentz Oken, who not only aroused a very wide interest in
this science by his _General Natural History_, but also put forward
some general observations of great value. His "infamous" theory of a
primitive slime, and the development of infusoria out of it, is merely
the fundamental idea of the theory of protoplasm and the cell which
was long afterwards fully recognized. These and other services of the
older natural philosophy were partly ignored and partly overlooked,
because they went far beyond the scientific horizon of the time, and
their authors to an extent lost themselves in airy and fantastic
speculations. The more scientists confined themselves in the following
half-century to empirical work and the observation and description of
separate facts, the more it became the fashion to look down on all
"natural philosophy." The most paradoxical feature of the situation was
that purely speculative philosophy and idealist metaphysics had a great
run at the same time, and their castles in the air, utterly destitute
of biological foundation, were much admired.

The magnificent reform of biology which Darwin initiated in 1859 by
his epoch-making _Origin of Species_ gave a fresh impulse to natural
philosophy. As this work not only used the rich collection of facts
already made in proof of the theory of descent, but gave it a new
foundation in the theory of selection (Darwinism properly so called),
everything seemed to call for the embodiment of the new conception of
nature in a monistic system. I made the first effort to do this in my
_General Morphology_ (1866). As this found few supporters among my
colleagues, I undertook in my _History of Creation_ (1868) to make
the chief points of the system accessible to the general reader. The
remarkable success of this book (a tenth edition of it appearing in
1902) emboldened me at the end of the nineteenth century to state the
general principles of my monistic philosophy in my _Riddle of the
Universe_. About the same time (1899) there appeared the work of the
Kiel botanist, Johannes Reinke, _The World as Reality_; and two years
afterwards he followed it up with a supplementary volume, _Introduction
to Theoretic Biology_. As Reinke treats the general problems of natural
philosophy from a purely mystic and dualistic point of view, his ideas
are diametrically opposed to my monistic and naturalistic principles.

The history of philosophy describes for us the infinite variety of
ideas that men have formulated during the last three thousand years
on the nature of the world and its phenomena. Überweg has given us,
in his excellent _History of Philosophy_, a thorough and impartial
account of these various systems. Fritz Schultze has published a
clear and compendious "tabulated outline" of them in thirty tables in
his genealogical tree of philosophy, and at the same time shown the
phylogeny of ideas. When we survey this enormous mass of philosophic
systems from the point of view of general biology, we find that we can
divide them into two main groups. The first and smaller group contains
the monistic philosophy, which traces all the phenomena of existence
to one single common principle. The second and larger group, to which
most philosophic systems belong, constitutes the dualistic philosophy,
according to which there are two totally distinct principles in the
universe. These are sometimes expressed as God and the world, sometimes
as the spiritual world and material world, sometimes as mind and
matter, and so on. In my opinion, this antithesis of monism and dualism
is the most important in the whole history of philosophy. All other
systems are only variations of one or the other of these, or a more or
less obscure combination of the two.

The form of monism which I take to be the most complete expression
of the general truth, and which I have advocated in my writings for
thirty-eight years, is now generally called hylozoism. This expresses
the fact that all substance has two fundamental attributes; as matter
(_hyle_) it occupies space, and as force or energy it is endowed with
sensation (_cf._ chapter xix.). Spinoza, who gave the most perfect
expression to this idea in his "philosophy of identity," and most
clearly treated the notion of substance (as the all-embracing essence
of the world), clothes it with two general attributes--extension
and thought. Extension is identical with real space, and thought
with (unconscious) sensation. The latter must not be confused with
conscious human thought; intelligence is not found in substance, but is
a special property of the higher animals and man. Spinoza identifies
his substance with nature and God, and his system is accordingly
called pantheism; but it must be understood that he rejects the
anthropomorphic, personal idea of deity.

A good deal of the infinite confusion that characterizes the conflicts
of philosophers over their systems is due to the obscurity and
ambiguity of many of their fundamental ideas. The words "substance"
and "God," "soul" and "spirit," "sensation" and "matter," are used
in the most different and changing senses. This is especially true
of the word "materialism," which is often wrongly taken to be
synonymous with monism. The moral bias of idealism against _practical_
materialism (or pure selfishness and sensualism) is forthwith
transferred to theoretical materialism, which has nothing to do with
it; and the strictures which are justly urged against the one are
most unjustifiably applied to the other. Hence it is important to
distinguish very carefully between these two meanings of materialism.

Theoretical materialism (or hylonism), as a realistic and monistic
philosophy, is right in so far as it conceives matter and force to be
inseparably connected, and denies the existence of immaterial forces.
But it is wrong when it denies all sensation to matter, and regards
actual energy as a function of dead matter. Thus, in ancient times
Democritus and Lucretius traced all phenomena to the movements of dead
atoms, as did also Holbach and Lamettrie in the eighteenth century.
This view is held to-day by most chemists and physicists. They regard
gravitation and chemical affinity as a mere mechanical movement of
atoms, and this, in turn, as the general source of all phenomena; but
they will not allow that these movements necessarily presuppose a
kind of (unconscious) sensation. In conversation with distinguished
physicists and chemists I have often found that they will not hear a
word about a "soul" in the atom. In my opinion, however, this must
necessarily be assumed to explain the simplest physical and chemical
processes. Naturally I am not thinking of anything like the elaborate
psychic action of man and the higher animals, which is often bound
up with consciousness; we must rather descend the long scale of the
development of consciousness until we reach the simplest protists,
the monera (chapter ix.). The psychic activity of these homogeneous
particles of plasm (for instance, the chromacea) rises very little
above that of crystals; as in the chemical synthesis in the moneron, so
in crystallization we are bound to assume that there is a low degree
of sensation (not of consciousness), in order to explain the orderly
arrangement of the moving molecules in a definite structure.

The prejudice against theoretical materialism (or materialistic monism)
which still prevails so much is partly due to its rejection of the
three central dogmas of dualist metaphysics, and partly to a confusion
of it with hedonism. This practical materialism in its extreme forms
(as Aristippus of Cyrene and the Cyrenaic school, and afterwards
Epicurus, taught it) finds the chief end of life in pleasure--at one
time crude, sensual pleasure, and at others spiritual pleasure. Up to a
certain point, this thirst for happiness and a pleasant and enjoyable
life is innate in every man and higher animal, and so far just; it only
began to be censured as sinful when Christianity directed the thoughts
of men to eternal life, and taught them that their life on earth was
only a preparation for the future. We shall see afterwards, when we
come to weigh the value of life (chapter xvii.), that this asceticism
is unjustifiable and unnatural. But as every legitimate enjoyment can
become wrong by excess, and every virtue be turned into vice, so a
narrow hedonism is to be condemned, especially when it allies itself
with egoism. However, we must point out that this excessive thirst for
pleasure is in no way connected with materialism, but is often found
among idealists. Many convinced supporters of theoretical materialism
(many scientists and physicians, for instance) lead very simple,
blameless lives, and are little disposed to material pleasures. On the
other hand, many priests, theologians, and idealist philosophers, who
preach theoretical idealism, are pronounced hedonists in practice.
In olden times many temples served at one and the same time for the
theoretic worship of the gods and for practical excesses in the way
of wine and love; and even in our day the luxurious and often vicious
lives of the higher clergy (at Rome, for instance) do not fall far
short of the ancient models. This paradoxical situation is due to the
special attractiveness of everything that is forbidden. But it is
utterly unjust to extend the natural feeling against excessive and
egoistic hedonism to theoretical materialism and to monism. Equally
unjust is the habit, still widely spread, of depreciating matter, as
such, in favor of spirit. Impartial biology has taught us of late years
that what we call "spirit" is--as Goethe said long ago--inseparably
bound up with matter. Experience has never yet discovered any spirit
apart from matter.

On the other hand, pure dynamism, now often called energism (and
often spiritualism), is just as one-sided as pure materialism. Just
as the latter takes one attribute of substance, matter, as the one
chief cause of phenomena, dynamism takes its second attribute, force
(_dynamis_). Leibnitz most consistently developed this system among
the older German philosophers; and Fechner and Zöllner have recently
adopted it in part. The latest development of it is found in Wilhelm
Ostwald's _Natural Philosophy_ (1902). This work is purely monistic,
and very ingeniously endeavors to show that the same forces are at
work in the whole of nature, organic and inorganic, and that these may
all be comprised under the general head of energy. It is especially
satisfactory that Ostwald has traced the highest functions of the
human mind (consciousness, thought, feeling, and will), as well as the
simplest physical and chemical processes (heat, electricity, chemical
affinity, etc.), to special forms of energy, or natural force. However,
he is wrong when he supposes that his energism is an entirely new
system. The chief points of it are found in Leibnitz; and other Leipzig
scientists, especially Fechner and Zöllner, had come very close to
similar spiritualistic views--the latter going into outright spiritism.
Ostwald's chief mistake is to take the terms "energy" and "substance"
to be synonymous. Certainly his universal, all-creating energy is, in
the main, the same as the substance of Spinoza, which we have also
adopted in our "law of substance." But Ostwald would deprive substance
of the attribute of matter altogether, and boasts of his _Refutation of
Materialism_ (1895). He would leave it only the one attribute, energy,
and reduce all matter to immaterial points of force. Nevertheless,
as chemist and physicist, he never gets rid of space-filling
substance--which is all we mean by "matter"--and has to treat it and
its parts, the physical molecules and chemical atoms (even if only
conceived as symbols), daily as "vehicles of energy." Ostwald would
reject even these in his pursuit of the illusion of a "science without
hypotheses." As a fact, he is forced every day, like every other exact
scientist, to assume and apply in practice the indispensable idea of
matter, and its separate particles, the molecules and atoms. Knowledge
is impossible without hypotheses.

Monism is best expressed as hylozoism, in so far as this removes
the antithesis of materialism and spiritualism (or mechanicism and
dynamism), and unites them in a natural and harmonious system. Our
monistic system has been charged with leading to pure naturalism;
one of its most vehement critics, Frederick Paulsen, attaches so
much importance to this stricture that he thinks it as dangerous
as dogmatic clericalism. We may, therefore, usefully consider the
idea of naturalism, and point out in what sense we accept it and
identify it with monism. The key to the position is in our monistic
anthropogeny, our unprejudiced conviction, supported by every branch
of anthropological research, of "man's place in nature," as we have
established it in the first section of the _Riddle_ (chapters ii.-v.).
Man is a purely natural being, a placental mammal of the order of
primates. He was phylogenetically evolved in the course of the
Tertiary Period from a series of the lower primates (directly from
the anthropoid apes, but earlier from the cynocephali and lemures).
Savage man, as we have him to-day in the Veddah or Australian negro, is
physiologically nearer to the apes than to highly civilized men.

Anthropology (in the widest sense) is only a particular branch of
zoology, to which we must assign a special position on account of its
extreme importance. Hence all the sciences which relate to man and his
psychic activity--especially what are called the moral sciences--must
be regarded from our monistic point of view as special branches of
zoology and as natural sciences. Human psychology is inseparably
connected with comparative animal psychology, and this again with
that of the plants and protists. Philology studies in human speech a
complicated natural phenomenon, which depends on the combined action
of the brain-cells of the phronema, the muscles of the tongue, and
the vocal cords of the larynx, as much as the cry of mammals and the
song of birds do. The history of mankind (which we, in our curious
anthropocentric mood, call the history of the world), and its highest
branch, the history of civilization, is connected by modern prehistoric
science directly with the stem-history of the primates and the other
mammals, and indirectly with the phylogeny of the lower vertebrates.
Hence, when we consider the subject without prejudice, we do not find
a single branch of human science that passes the limits of natural
science (in the broadest sense), any more than we find nature herself
to be supernatural.

Just as monism, or naturalism, embraces the totality of science, so on
our principles the idea of nature comprises the whole scientifically
knowable world. In the strict monistic sense of Spinoza the ideas
of God and Nature are synonymous for us. Whether there is a realm
of the supernatural and spiritual beyond nature we do not know. All
that is said of it in religious myths and legends, or metaphysical
speculations and dogmas, is mere poetry and an outcome of imagination.
The imagination of civilized man is ever seeking to produce unified
images in art and science, and when it meets with gaps in these in the
association of ideas it endeavors to fill them with its own creations.
These creations of the phronema with which we fill the gaps in our
knowledge are called _hypotheses_ when they are in harmony with the
empirically established facts, and _myths_ when they contradict the
facts: this is the case with religious myths, miracles, etc. Even
when people contrast mind with nature, this is only a result, as a
rule, of similar superstitions (animism, spiritism, etc.). But when we
speak of man's mind as a higher psychic function, we mean a special
physiological function of the brain, or that particular part of the
cortex of the brain which we call the phronema, or organ of thought.
This higher psychic function is a natural phenomenon, subject, like
all other natural phenomena, to the law of substance. The old Latin
word _natura_ (from _nasci_, to be born) stands, like the corresponding
Greek term _physis_ (from _phyo_--to grow), for the essence of the
world as an eternal "being and becoming"--a profound thought! Hence
physics, the science of the _physis_, is, in the broadest sense of the
word, "natural science."

The extensive division of labor which has taken place in science, on
account of the enormous growth of our knowledge in the nineteenth
century and the rise of many new disciplines, has very much altered
their relations to each other and to the whole, and has even given a
fresh meaning and connotation to the term. Hence by physics, as it is
now taught at the universities, is usually understood only that part of
inorganic science which deals with the molecular relations of substance
and the mechanism of mass and ether, without regard to the qualitative
differences of the elements, which are expressed in the atomic weight
of their smallest particles, the atoms. The study of the atoms and
their affinities and combinations belongs to chemistry. As this
province is very extensive and has its special methods of research,
it is usually put side by side with physics as of equal importance;
in reality, however, it is only a branch of physics--chemistry is
the physics of the atoms. Hence, when we speak of a physico-chemical
inquiry or phenomenon, we might justly describe it briefly as
_physical_ (in the wider sense). Physiology, again, a particularly
important branch of it, is in this sense the physics of living things,
or the physico-chemical study of the living body.

Since Aristotle dealt with the eternal phenomena of nature in the first
part of his works, and called this _physics_, and with their inner
nature in the second part, to which he gave the name of _metaphysics_,
the two terms have undergone many and considerable modifications. If
we restrict the term "physics" to the empirical study of phenomena (by
observation and experiment), we may give the name of metaphysics to
every hypothesis and theory that is introduced to fill up the gaps in
it. In this sense the indispensable theories of physics (such as the
assumption that matter is made up of molecules and atoms and electrons)
may be described as metaphysical; such also is our assumption that all
substance is endowed with sensation as well as extension (matter).
This monistic metaphysics, which recognizes the absolute dominion of
the law of substance in all phenomena, but confines itself to the
study of nature and abandons inquiry into the supernatural, is, with
all its theories and hypotheses, an indispensable part of any rational
philosophy of life. To claim, as Ostwald does, that science must be
free from hypotheses is to deprive it of its foundations. But it is
very different with the current dualistic metaphysics, which holds that
there are two distinct worlds, and which we find in a hundred forms as
philosophic dualism.

If we understand by metaphysics the science of the ultimate ground of
things, springing from the rational demand for causes, it can only
be regarded, from the physiological point of view, as a higher and
late-developed function of the phronema. It could only arise with the
complete development of the brain in civilized man. It is completely
lacking among savages, whose organ of thought rises very little
above that of the most intelligent animals. The laws of the psychic
life of the savage have been closely studied by modern ethnology. It
teaches us that the higher reason is not found in savages, and that
their power of abstract thought and of forming concepts is at a very
low level. Thus, for instance, the Veddahs, who live in the forests
of Ceylon, have not the general idea of trees, though they know and
give names to individual trees. Many savages cannot count up to five;
they never reflect on the ground of their existence or think of the
past or future. Hence it is a great error for Schopenhauer and other
philosophers to define man as a "metaphysical animal," and to seek
a profound distinction between man and the animal in the need for
a metaphysic. This craving has only been awakened and developed by
the progress of civilization. But even in civilized communities it
(like consciousness) is not found in early youth, and only gradually
emerges. The child has to learn to speak and think. In harmony with
our biogenetic law, the child reproduces in the various stages of its
mental development the whole of the gradations which lead from the
savage to the barbarian, and from the barbarian to the half-civilized,
and on to the fully educated man. If this historical development of
the higher human faculties had always been properly appreciated, and
psychology had been faithful to the comparative and genetic methods,
many of the errors of the current metaphysical systems would have been
avoided. Kant would not then have produced his theory of _a priori_
knowledge, but would have seen that all that now seems to be _a priori_
in civilized man was originally acquired by _a posteriori_ experiences
in the long evolution of civilization and science. Here we have the
root of the errors which are distinctive of dualism and the prevailing
metaphysical transcendentalism.

Like all science, biology is _realistic_--that is to say, it regards
its object, the organisms, as really existing things, the features of
which are to an extent knowable through our senses (_sensorium_) and
organ of thought (_phronema_). At the same time, we know that these
cognitive organs, and the knowledge they bring us, are imperfect, and
that there may be other features of organisms that lie beyond our means
of perception altogether. But it by no means follows from this that,
as our idealist opponents say, the organisms (and all other things)
exist only in our mind (in the images in our cortex). Our pure monism
(or hylozoism) agrees with realism in recognizing the unity of being
of each organism, and denying that there is any essential distinction
between its knowable phenomenon and its internal hidden essence (or
noumenon), whether the latter be called, with Plato, the eternal
"idea," or, with Kant, the "thing in itself." Realism is not identical
with materialism, and may even be definitely connected with the very
opposite, dynamism or energism.

As realism generally coincides with monism, so idealism is usually
identical with dualism. The two most influential representatives of
dualism, Plato and Kant, said that there were two totally distinct
worlds. Nature, or the empirical world, is alone accessible to our
experience, while the spiritual or transcendental world is not. The
existence of the latter is known to us only by the emotions or by
practical reason; but we can have no idea of its nature. The chief
error of this theoretical idealism is the assumption that the soul is
a peculiar, immaterial being, immortal and endowed with _a priori_
knowledge. The physiology and ontogeny of the brain (together with the
comparative anatomy and histology of the phronema) prove that the soul
of man is, like that of all other vertebrates, a function of the brain,
and inseparably bound up with this organ. Hence this idealist theory
of knowledge is just as inconsistent with realistic biology as is the
psycho-physical parallelism of Wundt or the psychomonism of more
recent physiologists, which in the end issues in a complete dualism of
body and mind. It is otherwise with _practical_ idealism. When this
presents the symbols or ideals of a personal God, an immortal soul, and
the free-will as ethical stimuli, and uses them for their pedagogical
worth in the education of the young, it may have a good influence for a
time, which is independent of their theoretical untenability.

The many branches of biology which have been developed independently
in the course of the nineteenth century ought to remain in touch
with one another, and co-operate with a clear apprehension of their
task, if they are to attain their high purpose of framing a unified
science embracing the whole field of organic life. Unfortunately, this
common aim is often lost sight of in the specialization of study;
the philosophical task is neglected in favor of the empirical. The
confusion that has ensued makes it desirable to determine the mutual
positions of the various biological disciplines. I went into this
somewhat fully in my academic speech on the development and aim of
zoology in 1869. But as this essay is little known, I will briefly
resume the chief points of it.

In correspondence with the long-established distinction between the
plant and the animal, the two chief branches of biology, zoology
and botany, have developed side by side, and are represented by
two different chairs in the universities. Independently of these,
there arose at the very beginning of scientific activity that field
of inquiry which deals with human life in all its aspects--the
anthropological disciplines and the so-called "mental sciences"
(history, philology, psychology, etc.). Since the theory of descent has
proved man's origin from vertebrate ancestors, and thus anthropology
has been recognized as a part of zoology, we have begun to understand
the inner historic connection between these various branches of
anthropology, and to combine them in a comprehensive science of man.
The immense extent and the great importance of this science have
justified the creation of late years of special chairs of anthropology.
It seems desirable to do the same for the science of the protists, or
unicellular organisms. The cell theory, or cytology, as an elementary
part of anatomy, has to be dealt with in both botany and zoology;
but the lowest unicellular representatives of both kingdoms, the
primitive plants (protophyta) and the primitive animals (protozoa), are
so intimately connected, and throw so great a light, as independent
rudimentary organisms, on the tissue cells in the _histon_, or
multicellular organism, that we must regard as a sign of progress the
recent proposal of Schaudinn to found a special institute and journal
for the science of protists. One very important section of it is
bacteriology.

The practical division of biology, according to the extent of the
organic kingdom, leads us to mark out four chief provinces of research:
protistology (the science of the unicellulars), botany (the science
of plants), zoology (the science of animals), and anthropology (the
science of man). In each of these four fields we may then distinguish
morphology (the science of forms) and physiology (the science of
functions) as the two chief divisions of scientific work. The special
methods and means of observation differ entirely in the two sections.
In morphology the work of description and comparison is the most
important as regards both outer form and inner structure. In physiology
the exact methods of physics and chemistry are especially demanded--the
observation of vital activities and the attempt to discover the
physical laws that govern them. As a correct knowledge of human anatomy
and physiology is indispensable for scientific medicine, and the work
requires a particularly large apparatus, these two sciences have long
been studied separately, and have been handed over to the medical
facility in the division of the academic curriculum.

The broad field of morphology may be divided into anatomy and
biogeny; the one deals with the fully developed, and the other
with the developing, organism. Anatomy, the study of the formed
organism, studies both the external form and the inner structure.
We may distinguish as its two branches the science of structures
(tectology) and the science of fundamental forms (promorphology).
Tectology investigates the features of the structure in the organic
_individual_, and the composition of the body out of various parts
(cells, tissues, and organs). Promorphology describes the real form of
these individual parts and of the whole body, and endeavors to reduce
them mathematically to certain fundamental forms (chapter viii.).
Biogeny, or the science of the evolution of organisms, is also divided
into two parts--the science of the individual (ontogeny) and of the
stem or species (phylogeny); each follows its own peculiar methods
and aims, but they are most intimately connected by the biogenetic
law. Ontogeny deals with the development of the individual organism
from the beginning of its existence to death; as embryology it
observes the growth of the individual within the fœtal membranes;
and as metamorphology (or the science of metamorphoses) it follows
the subsequent changes in post-fœtal life (chapter xvi.). The
task of phylogeny is to trace the evolution of the organic stem or
species--that is to say, of the chief divisions in the animal and
plant worlds, which we describe as classes, orders, etc.; in other
words, it traces the genealogy of species. It relies on the facts of
paleontology, and fills up the gaps in this by comparative anatomy and
ontogeny.

The science of the vital phenomena, which we call physiology, is for
the most part the physiology of work, or ergology; it investigates
the functions of the living organism, and has to reduce them as
closely as possible to physical and chemical laws. Vegetable ergology
deals with what are called the vegetative functions, nutrition and
reproduction; animal ergology studies the animal activities of movement
and sensation. Psychology is directly connected with the latter.
But the study of the relations of the organism to its environment,
organic and inorganic, also belongs to physiology in the wider sense;
we call this part of it perilogy, or the physiology of relations. To
this belong chorology, or the science of distribution (also called
biological geography, as it deals with geographical and topographical
distribution), and œcology or bionomy (also recently called
ethology), the science of the domestic side of organic life, of the
life-needs of organisms and their relations to other organisms with
which they live (biocenosis, symbiosis, parasitism).

THIRD TABLE

SYNOPSIS OF THE CHIEF BRANCHES OF BIOLOGY (1869)

BIOLOGY = THE SCIENCE OF LIFE

       The four chief branches of systematic biology.

    I. Protistology = the science of single cells--unicellular organisms.
   II. Botany = the science of plants--tissue plants (metaphyta).
  III. Zoology = the science of animals--tissue animals (metazoa).
   IV. Anthropology = the science of man--speaking primates.

  ┌───────────────────────────────────────────────────────────────────────┐
  │      A. MORPHOLOGY = THE SCIENCE OF FORMS.                            │
  │         Anatomy and biogeny of organisms.                             │
  ├────────────────────────────────────┬──────────────────────────────────┤
  │A I. ANATOMY.                       │A II. BIOGENY.                    │
  │The science of structure.           │The science of development.       │
  │1. TECTOLOGY.                       │3. PHYLOGENY.                     │
  │The science of structure.           │Stem history.                     │
  │Cytology, science of cells.         │Paleontology and genealogy.       │
  │Histology, science of tissues.      │Transformism or theory of descent.│
  │Organology, science of organs.      │Natural classification.           │
  │Blastology, science of persons.     │                ────              │
  │Kormology, science of trunks.       │                                  │
  │              ────                  │4. ONTOGENY.                      │
  │2. PROMORPHOLOGY.                   │4_a_. Embryology.                 │
  │The science of fundamental          │(Development within the           │
  │forms. Knowledge of the geometrical │fœtal membranes.)                 │
  │ideal forms (mathematically         │4_b_. Metamorphology.             │
  │definable) in relation              │(Modification of the organism     │
  │to the concrete real form of        │after fœtal life.)                │
  │the individual.                     │                                  │
  └────────────────────────────────────┴──────────────────────────────────┘
  ┌──────────────────────────────────────────────────────────────────┐
  │       B. PHYSIOLOGY = THE SCIENCE OF FUNCTIONS.                  │
  │          Physics and chemistry of the organism.                  │
  ├─────────────────────────────┬────────────────────────────────────┤
  │B I. ERGOLOGY.               │B II. PERILOGY.                     │
  │ Physiology of work.         │Physiology of relations.            │
  │5. Vegetal ergology.         │7. Chorology.                       │
  │Physiology of the vegetative │The science of distribution.        │
  │functions.                   │Biological geography and topography.│
  │5_a_. Trophonomy.            │The science of migrations.          │
  │The science of metabolism.   │                                    │
  │5_b_. Gonimatology.          │                ────                │
  │The science of reproduction. │                                    │
  │          ────               │                                    │
  │6. Animal ergology.          │8. ŒCOLOGY.                         │
  │6_a_. Phoronomy.             │(or bionomy or ethology).           │
  │The science of movement.     │The science of domestic life.       │
  │6_b_. Sensonomy.             │Biological economy.                 │
  │The science of sensation.    │Relations of the organism to        │
  │6_c_. Psychology.            │the environment, and to other       │
  │                             │organisms with which it lives.      │
  └─────────────────────────────┴────────────────────────────────────┘




V

DEATH

 Life and death--Individual death--Immortality
 of the unicellulars--Death of the protists and
 tissue-organisms--Causes of physiological death--Using up
 of the plasma--Regeneration--Biotonus--Perigenesis of the
 plastidules: memory of the biogens--Regeneration of protists and
 tissue-organisms--Senile debility--Disease--Necrobiosis--The lot
 of death--Providence--Chance and fate--Eternal life--Optimism
 and pessimism--Suicide and self-redemption--Redemption from
 evil--Medicine and philosophy--Maintenance of life--Spartan selection.


Nothing is constant but change! All existence is a perpetual flux
of "being and becoming"! That is the broad lesson of the evolution
of the world, taken as a whole or in its various parts. Substance
alone is eternal and unchangeable, whether we call this all-embracing
world-being Nature, or Cosmos, or God, or World-spirit. The law of
substance teaches us that it reveals itself to us in an infinite
variety of forms, but that its essential attributes, matter and
energy, are constant. All individual forms of substance are doomed
to destruction. That will be the fate of the sun and its encircling
planets, and of the organisms that now people the earth--the fate
of the bacterium and of man. Just as the existence of every organic
individual had a beginning, it will also undeniably have an end. Life
and death are irrevocably united. However, philosophers and biologists
hold very different views as to the real causes of this destiny. Most
of their opinions are at once out of court, because they have not a
clear idea of the nature of life, and so can have no adequate idea of
its termination--death.

The inquiry into the nature of organic life which we instituted
in the second chapter has shown us that it is, in the ultimate
analysis, a chemical process. The "miracle of life" is in essence
nothing but the metabolism of the living matter, or of the plasm.
Recent physiologists, especially Max Verworn and Max Kassowitz, have
pointed out, in opposition to modern vitalism, that "life consists
in a continuous alternation between the upbuild and the decay of the
highly complicated chemical unities of the protoplasm. And if this
conception is admitted, we may rightly say that we know what we mean
by death. If death is the cessation of life, we must mean by that the
cessation of the alternation between the upbuild and the dissolution
of the molecules of protoplasm; and as each of the molecules of
protoplasm must break up again shortly after its formation, we have in
death to deal only with the definite cessation of reconstruction in
the destroyed plasma-molecules. Hence a living thing is not finally
dead--that is to say, absolutely incompetent to discharge any further
vital function--until the whole of its plasma-molecules are destroyed."
In the exhaustive justification with which Kassowitz follows up this
definition in the fifteenth chapter of his _General Biology_, the
natural causes of physiological death are fully described.

Among the numerous and contradictory views of recent biologists on
the nature of death we find many errors and misunderstandings, due
to a lack of clear distinction between the duration of the living
matter in general and that of the individual life-form. This is
particularly noticeable in the contradictory views which have been
elicited by August Weismann's theory (1882) of the immortality of the
unicellulars. I have shown in the eleventh chapter of the _Riddle_ that
it is untenable. But as the distinguished zoologist has again taken
up his theory with energy in his instructive _Lectures on the Theory
of the Descent_ (1902), and has added to it erroneous observations on
the nature of death, I am obliged to return to the point. Precisely
because this interesting work gives most valuable support to the
theory of evolution, and maintains Darwin's theory of selection and
its consequences with great effect, I feel it is necessary to point
out considerable weaknesses and dangerous errors in it. The chief of
these is the important theory of the germ-plasm and the consequent
opposition to the inheritance of acquired characteristics. Weismann
deduces from this a radical distinction between the unicellular and
the multicellular organisms. The latter alone are mortal, the former
immortal; "between the unicellular and the multicellular lies the
introduction of physiological--that is to say, normal--death." We
must say, in opposition to this, that the physiological individuals
(_bionta_) among the protista are just as limited in their duration as
among the histona. But if the chief stress in the question is laid,
not on the individuality of the living matter, but on the continuity
of the metabolic life-movement through a series of generations, it is
just as correct to affirm a partial immortality of the plasm for the
multicellulars as for the unicellulars.

The immortality of the unicellulars, on which Weismann has laid so much
stress, can only be sustained for a small part of the protists even in
his own sense--namely, for those which simply propagate by cleavage,
the chromacea and bacteria among the monera (chapter ix.), the diatomes
and paulotomes among the protophyta, and a part of the infusoria and
rhizopods among the protozoa. Strictly speaking, the individual life is
destroyed when a cell splits into two daughter-cells. One might reply
with Weismann that in this case the dividing unicellular organism
lives on as a whole in its offspring, and that we have no corpse, no
dead remains of the living matter, left behind. But that is not true of
the majority of the protozoa. In the highly developed ciliata the chief
nucleus is lost, and there must be from time to time a conjugation of
two cells and a mutual fertilization of their secondary nuclei, before
there can be any further multiplication by simple cleavage. However,
in most of the sporozoa and rhizopoda, which generally propagate by
spore formation, only one portion of the unicellular organism is used
for this; the other portion dies, and forms a "corpse." In the large
rhizopods (thalamophora and radiolaria) the spore-forming inner part,
which lives on in the offspring, is smaller than the decaying outer
portion, which becomes the corpse.

Weismann's view of the secondary "introduction of physiological death
in the multicellulars" is just as untenable as his theory of the
immortality of the unicellulars. According to this opinion, the death
of the histona--both the metaphyta and metazoa--is a purposive outcome
of adaptation, only introduced by selection when the multicellular
organism has reached a certain stage of complexity of structure, which
is incompatible with its original immortality. Natural selection would
thus kill the immortal and preserve only the mortal; it would interfere
with the multiplication of the immortals in the bloom of their years,
and only use the mortal for rearing posterity. The curious conclusions
which Weismann reached in developing this theory of death, and the
striking contradictions to his own theory of the germ-plasm which
he fell into, have been pointed out by Kassowitz in the forty-ninth
chapter of his _General Biology_. In my opinion, this paradoxical
theory of death has no more basis than the germ-plasm theory he has
ingeniously connected with it. We may admire the subtlety and depth
of the speculations with which Weismann has worked out his elaborate
molecular theory. But the nearer we get to its foundations the less
solid we find them. Moreover, not one of the many supporters of the
theory of germ-plasm has been able to make profitable use of it in the
twenty years since it was first published. On the other hand, it has
had an evil influence in so far as it denied the inheriting of acquired
characters, which I hold, with Lamarck and Darwin, to be one of the
soundest and most indispensable supports of the theory of descent.

In discussing the question of the real causes of death, we confine our
attention to normal or physiological death without considering the
innumerable causes of accidental or pathological death, by illness,
parasites, mishaps, etc. Normal death takes place in all organisms when
the limit of the hereditary term of life is reached. This limit varies
enormously in different classes of organisms. Many of the unicellular
protophyta and protozoa live only a few hours, others several months
or years; many one-year plants and lower animals live only a summer in
our temperate climate, and only a few weeks or months in the arctic
circle or on the snow-covered Alps. On the other hand, the larger
vertebrates are not uncommonly a hundred years old, and many trees live
for a thousand years. The normal span of life has been determined in
all species in the course of their evolution by adaptation to special
conditions, and has then been transmitted to offspring by heredity. In
the latter, however, it is often subject to considerable modifications.

The organism has been compared, on the modern "machine theory" of life,
to an artificially constructed mechanism, or an apparatus in which the
human intelligence has put together various parts for the attainment of
a certain end. This comparison is inapplicable to the lowest organisms,
the monera, which are devoid of such a mechanical structure. In these
primitive "organisms without organs" (chromacea and bacteria) the sole
cause of life is the invisible chemical structure of the plasm and the
metabolism effected by this. As soon as this ceases death takes place
(_cf._ chapter ix.). In the case of all other organisms the comparison
is useful in so far as the orderly co-operation of the various organs
or parts accomplishes a certain task by the conversion of virtual
into active force. But the great difference between the two is that
in the case of the machine the regularity is due to the purposive and
consciously acting will of man, whereas in the case of the organism it
is produced by unconscious natural selection without any design. On
the other hand, the two have another important feature in common in
the limited span of life which is involved in their being used up. A
locomotive, ship, telegraph, or piano, will last only a certain number
of years. All their parts are worn out by long use, and, in spite of
all repairing, become at last useless. So in the case of all organisms,
the various parts are sooner or later worn out and rendered useless;
this is equally true of the organella of the protist and the organs of
the histon. It is true that the parts may be repaired or regenerated;
but sooner or later they cease to be of service, and become the cause
of death.

When we take the idea of regeneration, or the recuperation of parts
that have been rendered useless, in the widest sense, we find it to
be a universal vital function of the greatest importance. The whole
metabolism of the living organism consists in the assimilation of
plasm, or the replacing of the plasma-particles which are constantly
used up by dissimilation (_cf._ chapter x.). Verworn has given the name
of _biogens_ to the hypothetical molecules of living matter--which
I regard with Hering as endowed with memory, and (1875) have called
plastidules. He says: "The biogens are the real vehicles of life.
In their constant decay and reconstruction consists the process of
life, which expresses itself in the great variety of vital phenomena."
The relation of assimilation (the building-up of the biogens) to
dissimilation (the decay of the biogens) may be expressed by a fraction
to which the name _biotonus_ is given A/D. It is of radical importance
in the various phenomena of life. The variations in the size of this
fraction are the cause of all change in the life-expression of every
organism. When the biotone increases, and the metabolism quotient
becomes more than one, we have growth; when, on the other hand, it
falls below one, and the biotone decreases, we have atrophy, and
finally death. New biogens are constructed in _regeneration_. In
_generation_ or reproduction groups of biogens (as germ-plasm) are
released from the parent in consequence of redundant growth, and form
the foundation of new individuals.

The phenomena of regeneration are extremely varied, and have of
late years been made the subject of a good deal of comprehensive
experiment, especially on the side of what is called "mechanical
embryology." Many of these experimental embryologists have drawn
far-reaching conclusions from their somewhat narrow experiments, and
have partly urged them as objections to Darwinism. They imagine that
they have disproved the theory of selection. Most of these efforts
betray a notable lack of general physiological and morphological
knowledge. As they also generally ignore the biogenetic law, and
take no account of the fundamental correlation of embryology and
stem history, we can hardly wonder that they reach the most absurd
and contradictory conclusions. Many examples of this will be found
in the _Archiv für Entwickelungsmechanik_. When, however, we make
a comprehensive survey of the interesting field of regeneration
processes, we discover a continuous series of development from
the simplest repair of plasm in the unicellular protists to the
sexual generation of the higher histona. The sperm-cells and ova
of the latter are redundant growth-products, which have the power
of regenerating the whole multicellular organism. But many of the
higher histona have also the capacity to produce new individuals by
regeneration from detached pieces of tissue, or even single cells.
In the peculiar mode of metabolism and growth which accompanies
these processes of regeneration, the memory of the plastidule, or
the unconscious retentive power of the biogens, plays the chief part
(_cf._ my _Perigenesis of the Plastidule_, 1875). In the most primitive
kinds of the unicellular protists we find the phenomena of death and
regeneration in the simplest form. When an unnucleated moneron (a
chromaceum or bacterium) divides into two equal halves, the existence
of the dividing individual comes to an end. Each half regenerates
itself in the simplest conceivable way by assimilation and growth,
until it, in turn, reaches the size of the parent organism. In the
nucleated cells of most of the protophyta and protozoa it is more
complicated, as the nucleus becomes active as the central organ and
regulator of the metabolism. If an infusorium is cut into two pieces,
only one of which contains the nucleus, this one alone grows into a
complete nucleated cell; the unnucleated portion dies, being unable to
regenerate itself.

In the multicellular body of the tissue-forming organisms we must
distinguish between the partial death of the various cells and the
total death of the whole organism, or cell-state, which they make up.
In many of the lower tissue-plants and tissue-animals the communal
link is very loose and the centralization slight. Odd cells or groups
of cells may be set loose, without any danger to the life of the
whole histon, and grow into new individuals. In many of the algæ
and liverworts (even in the _bryophyllum_, closely related to the
stone-crop, or _sedum_)--as well as in the common fresh-water polyp,
hydra, and other polyps--every bit that is cut off is capable of
growing into a complete individual. But the higher the organization
is developed and the closer the correlation of the parts and their
co-operation in the life of the centralized stock or person, the
slighter we find the regenerative faculty of the several organs. Even
then, however, many used-up cells may be removed and replaced by
regenerated new cells. In our own human organism, as in that of the
higher animals, thousands of cells die every day, and are replaced
by new cells of the same kind, as, for instance, epidermic cells at
the surface of the skin, the cells of the salivary glands or the
mucous lining of the stomach, the blood-cells, and so on. On the other
hand, there are tissues that have little or nothing of this repairing
power, such as many of the nerve-cells, sense-cells, muscle-cells,
etc. In these cases a number of constant cell-individuals remain with
their nucleus throughout life, although a used-up portion of their
cell-body may be replaced by regeneration from the cytoplasm. Thus
our human body, like that of all the higher animals and plants, is a
"cell-state" in another sense. Every day, nay, every hour, thousands
of its citizens, the tissue-cells, pass away, and are replaced by
others that have arisen by cleavage of similar cells. Nevertheless,
this uninterrupted change of our personality is never complete or
general. There is always a solid groundwork of conservative cells, the
descendants of which secure the further regeneration.

Most organisms meet their death through external or accidental
causes--lack of sufficient food, isolation from their necessary
environment, parasites and other enemies, accidents and disease. The
few individuals who escape these accidental causes of death find the
end of life in old age or senility, by the gradual decay of the organs
and dwindling of their functions. The cause of this senility and the
ensuing natural death is determined for each species of organisms by
the specific nature of their plasm. As Kassowitz has lately pointed
out, the senility of individuals consists in the inevitable increase
in the decay of protoplasm and the metaplastic parts of the body
which this produces. Each metaplasm in the body favors the inactive
break-up of protoplasm, and so also the formation of new metaplasms.
The death of the cells follows, because the chemical energy of the
plasm gradually falls off from a certain height, the acme, of life.
The plasm loses more and more the power to replace by regeneration the
losses it sustains by the vital functions. As, in the mental life, the
receptivity of the brain and the acuteness of the senses gradually
decay, so the muscles lose their energy, the bones become fragile, the
skin dry and withered, the elasticity and endurance of the movements
decrease. All these normal processes of senile decay are caused by
chemical changes in the plasm, in which dissimilation gains constantly
on assimilation. In the end they inevitably lead to normal death.

While the gradual decay of the bodily forces and the senile
degeneration of the organs must necessarily cause the death of the
soundest organism in the end, the great majority of men pass away
through illness long before this normal term of life is reached. The
external causes of this are the attacks of enemies and parasites,
accidents, and unfavorable conditions of life. These cause changes
in the tissues and their component cells, which first occasion the
partial death of particular sections, and then the total death of the
whole individual. The modifications of the living matter which produce
disease and premature death are called _necrobioses_. They consist
partly of _histolyses_--that is to say, degeneration of the cells by
atrophy, dissolution, withering (mortification), or colliquation; and
partly of _metaplasmosisms_, or metamorphoses of the plasm--fatty,
mucous, chalky, or amyloid metamorphoses of the cells. It was the great
merit of Rudolph Virchow that he proved, in his epoch-making _Cellular
Pathology_ (1858), that all diseases in man and other organisms may be
reduced to such modifications of the cells which make up the tissues.
Hence disease, with its pain, is a physiological process, a life under
injurious and dangerous conditions. As in all normal vital phenomena,
so in abnormal or pathological, the ultimate ground must be sought in
the physical and chemical processes in the plasm. Pathology is a part
of physiology. This discovery has cut the ground from under the older
notion of disease as a special entity, a devil, or a divine punishment.

The natural physical explanation of death, which has been made possible
by modern physiology and pathology, has shattered, not only all the
old superstitious ideas about disease and death, but also a number of
important metaphysical dogmas which built upon them. Such was, for
instance, the naïve belief in a conscious Providence, controlling
the fate of individuals and determining their death. I do not fail
to appreciate the great subjective value which such a trust in a
protecting Providence has for men amid their countless dangers. We may
envy the childish temper for the confidence and hope which it derives
from this belief. But as we do not seek to have our emotions gratified
by poetic fictions, we are bound to point out that reason cannot detect
the shadow of a proof of the existence and action of this conscious
Providence, or "loving Father in heaven." We read daily in our journals
of accidents and crimes of all kinds that cause the unexpected death
of happy human beings. Every year we read with horror the statistics
of the thousands of deaths from shipwreck and railway accidents,
earthquakes and landslips, wars and epidemics. And then we are asked
to believe in a loving Providence that has decreed the death of each
of these poor mortals! We are asked to console ourselves in face of
the tragedy with the hollow phrases: "God's will be done," or "God's
ways are wonderful." Simple children and dull believers may soothe
themselves with such phrases. They no longer impose on educated people
in the twentieth century, who prefer a full and fearless knowledge of
the truth.

When our monistic and rational conception of death is described as
dreary and hopeless, we may answer that the prevalent dualistic view is
merely an outcome of hereditary habits of thought and mystic training
in early youth. When these are displaced by progressive culture and
science, it will be clear that man has lost nothing, but gained much,
as regards his life on earth. Convinced that there is no eternal life
awaiting him, he will strive all the more to brighten his life on
earth and rationally improve his condition in harmony with that of his
fellows. If it is objected that then everything will depend on mere
"chance," instead of being controlled by a conscious Providence or a
moral order of the world, I must refer the reader for my reply to the
close of the fourteenth chapter of the _Riddle_, where I have dealt
with fate, providence, end, aim, and chance. And if it is further
claimed that our realistic view of life leads to pessimism, there is no
better ground for such an accusation.

I have given, in the eleventh chapter of the _Riddle_, the scientific
reasons which forbid us to accept the personal immortality of the soul.
But as the most vehement attacks have been made on this chapter by
metaphysicians of the prevailing school and by Christian theologians,
I must return to the question here. I am convinced, from numbers of
letters I have received and conversation with educated people of all
classes, that no other dogma is so firmly established and highly valued
as athanatism, or the belief in personal immortality. Most men will not
give up at any price the hope that a better life awaits them beyond
the grave, which will compensate them for all the pain and suffering
they endure here. In the picturing of this future life the mediæval
geocentric idea still forms the chief feature. Troelslund has shown, in
his _Idea of Heaven and of the World_, how this theory still dominates
the metaphysics of the majority of men; in spite of Copernicus and
Laplace, heaven is still for most people the semicircular blue glass
bell that overarches the earth. We still hear the praises of our life
in this heaven sung daily in sermons and speeches and festive orations.
The orator extends his right hand "upward" to the infinite starry
space of heaven, forgetting that the radius of the direction he is
pointing towards changes every second, and in twelve hours reaches the
precisely opposite direction, and becomes "downward." Other believers
endeavor to be still more concrete, and point out definite celestial
bodies as the homes of immortal souls. Modern cosmology, astronomy, and
geology entirely exclude these pretty fictions from science; and modern
psychology, physiology, ontogeny, and phylogeny rigorously refuse an
inch of ground for athanatism.

Optimism regards the world on its good and bright and admirable
side: pessimism looks to the shades and tragedies of life. In some
philosophic and religious systems one or other of these tendencies
is consistently and exclusively worked out; but in most systems the
two are mingled. Pure and consistent realism is generally neither
optimistic nor pessimistic. It takes the world as it is, a unified
whole, the nature of which is neither good nor bad. Dualistic idealism,
however, generally combines the two, and distributes them between
its two worlds; it describes this world as a "vale of tears," and
the next as a glorious city of joy and happiness. This view is a
conspicuous feature in most of the dualistic religions, and has still
a considerable influence, both practically and theoretically, on the
minds of educated people.

The founder of systematic optimism was Gottfried Leibnitz, whose
philosophy sought to achieve an ingenious harmony between divergent
systems, but is really a form of dynamism, or a monism somewhat akin to
the energism of Ostwald. Leibnitz gave a compendious statement of his
system in his _Monadology_ (1714). He taught that the world consists of
an infinite number of monads (which almost correspond to our psychic
atoms), but this pluralism was converted into a monism by making God,
as the central monad, bind all together in a substantial unity. In
his _Theodicy_ (1710) he taught that God (the "all-wise, all-good,
and almighty creator of the world") had with perfect consciousness
created "the best of all possible worlds"; that his infinite goodness,
wisdom, and power are seen everywhere in the pre-established harmony
of things; but that the individual human being, and humanity taken as
a whole, have only a limited capacity for development. The man who
knows the real features of the world, who has honestly confronted the
tragic struggle for life that rules throughout living nature, who has
sympathy for the infinite sum of misery and want of every kind in the
life of men, can scarcely understand how an acute and informed thinker
like Leibnitz could entertain such optimism as this. It would be more
intelligible in the case of a one-sided and nebulous metaphysician like
Hegel, who held that "all that is real is rational and all that is
rational is real."

Pessimism is the direct opposite of systematic optimism. While the
one holds the universe to be the best, the other regards it as the
worst, of all possible worlds. This pessimistic conception has found
expression in the oldest and most popular religions of Asia, Brahmanism
and Buddhism. Both these Hindoo religions were originally pessimistic,
and at the same time atheistic and idealistic. Schopenhauer especially
pointed out this, declaring that they were the most perfect of all
religions, and importing their leading ideas into his own system. He
considers it "a glaring absurdity to attempt to prove this miserable
world the best of all possible ones--this cock-pit of tortured and
suffering beings, who can only survive by destroying one another, in
which the capacity for pain grows with knowledge, and so reaches its
height in man. Truly optimism cuts so sorry a figure in this theatre of
sin, suffering, and death that we should have to regard it as a piece
of sarcasm if Hume had not given us an explanation of its origin (the
wish to flatter God and hope for some result from it). To the palpable
sophistry of Leibnitz, who would prove this world the best of all
possible, we can oppose a strict and honest proof that it is the worst
of all possible." However, neither Schopenhauer nor the most important
of modern pessimists, Edward Hartmann, has drawn the strict practical
conclusion from pessimism. That would be to deny the will to live, and
put an end to suffering by suicide.

The mention of suicide as the logical consequence of pessimism may
serve as an occasion to glance at the curious and contradictory views
that are expressed about it. There are few problems of life (apart
from immortality and the freedom of the will) on which such absurd
and contradictory things have been said even down to our own time.
The theist who regards life as a gift of God may hesitate to reject
or return it--although the offering of one's self as a victim for
other men is considered a high virtue. Most educated people still look
upon suicide as a great sin, and in some countries (such as England)
the attempt is punished by law. In the Middle Ages, when a hundred
thousand men were burned alive for heresy or witchcraft, suicides
were punished by a disgraceful burial. As Schopenhauer says: "Clearly
there is nothing in the world to which a man has a plainer right than
his own life and person. It is simply ridiculous for criminal justice
to deal with suicide." The advance of embryology in the last thirty
years has made it clear that the individual life of a man (and all
other vertebrates) begins at the moment when the male sperm-cell and
the maternal ovum coalesce. In this blind chance plays an important
part, as in so many other important aspects of life--taking "chance"
in the scientific sense, which I have explained in chapter xiv. of
the _Riddle_. Hence, the real cause of personal existence is not the
favor of the Almighty, but the sexual love of one's earthly parents;
very often this consequence of the act of love has been anything but
desired. If, then, the circumstances of life come to press too hard
on the poor being who has thus developed, without any fault of his,
from the fertilized ovum--if, instead of the hoped-for good, there
come only care and need, sickness and misery of every kind--he has the
unquestionable right to put an end to his sufferings by death. Every
religion assents to this under certain conditions, even Christianity
when it says: "If thine eye scandalize thee, cast it from thee." It
is true that the conventional morality condemns suicide under any
circumstances; but the reasons it alleges are ridiculously slight, and
are not improved by having the mantle of religion wrapped about them.

The voluntary death by which a man puts an end to intolerable suffering
is really an act of redemption. We should, therefore, describe it as
self-redemption, and look on it with Christian sympathy, not brand it
pharisaically as "self-murder." As a fact, this contemptuous phrase
has no meaning, since murder is the taking away of a man's life against
his will, while the suicide dies voluntarily. Hence, he usually
deserves our sympathy, not contempt, and certainly not punishment.
Our conventional morality is, as so often happens, full of senseless
contradictions. Modern states have introduced conscription; they demand
that every citizen shall give up his life for his country on command,
and kill as many other men as he can (an admirable commentary on the
Scriptural "Love your enemies") for some political reason or other.
But they never secure to each citizen the means of honorable existence
and free development of his personality--not even the right to work by
which he may maintain himself and his family.

I fully recognize the advance that social politics has made in
improving the conditions of the poorer classes, the promotion of
hygiene and education and the bodily and mental welfare of citizens;
but we are still very far from the attainable ideal of general
prosperity and happiness which reason dictates to every civilized
nation. Misery and want are increasing among the poor, as the division
of labor and over-population increase. Thousands of strong and active
men come to grief every year without any fault of theirs, often
precisely because they were quiet and honest; thousands are hungry
because, with the best will in the world, they cannot find work;
thousands are sacrificed to the heartless demands of our iron age of
machinery with its exacting technical and industrial requirements. On
the other hand, we see thousands of contemptible characters prospering
because they have been able to deceive their fellows by unscrupulous
speculations, or because they have flattered and served the higher
authorities. It is no wonder that the statistics of suicide increase so
much in the more civilized communities. No feeling man who has any real
"Christian love of his neighbor" will grudge his suffering brother the
eternal rest and the freedom from pain which he has obtained by his
self-redemption.

The seventh petition of the Lord's Prayer, which is repeated daily by
millions of Christians, is: "Deliver us from evil." Luther explains
this as a prayer to be saved "from all evil of body and soul" in
this life and the next. When we consider this in the light of our
monistic principles, we have naturally to set aside the superstitious
ideas of the Middle Ages regarding the future life, and deal only
with the petition as regards this life. The number and variety and
gravity of these evils have grown in civilized communities in the
nineteenth century, notwithstanding all the progress we have made in
art and science and the rational reform of our personal and social
life. Civilization has gained infinitely in value by the change we
have made in our conceptions of time and space in this age of steam
and electricity. We can make our domestic and public life much
pleasanter, and avail ourselves of a far greater number of luxuries,
than was possible to our grandfathers a hundred years ago. But all
this has caused a much greater expenditure of nerve-energy. The brain
has to bear a much greater strain, and is worn out earlier, the body
is more stimulated and overworked than it was a hundred years ago.
Many diseases of modern civilization are making appalling progress;
neurasthenia, especially, and other diseases of the nerves, carry off
more victims every year. Our asylums grow bigger and more numerous
every year, and we have sanatoria on every side in which the baited
victim of modern civilization seeks refuge from his evils. Some of
these evils are quite incurable, and the sufferers have to meet a
certain death in terrible pain. Many of these poor creatures look
forward to their redemption from evil and the end of their miserable
lives. The important question arises whether, as compassionate men,
we should be justified in carrying out their wish and ending their
sufferings by a painless death.

This question is of great importance, both in practical philosophy
and in juridical and medical practice, and, as opinions differ very
much on the subject, it seems advisable to deal with it here. I start
from my own personal opinion, that sympathy is not only one of the
noblest and finest functions of the human brain, but also one of
the first conditions of the social life of the higher animals. The
precepts of Christian charity which the gospels rightly place in the
very foreground of morality, were not first discovered by Christ, but
they were successfully urged by him and his followers at a time when
refined selfishness threatened the Roman civilization with decay.
These natural principles of sympathy and altruism had arisen thousands
of years before in human society, and are even found among all the
higher animals that live a social life. They have their first roots
in the sexual reproduction of the lower animals, the sexual love and
the care of the young on which the maintenance of the species depends.
Hence the modern prophets of pure egoism, Friedrich Nietzsche, Max
Stirner, etc., commit a biological error when they would substitute
their morality of the strong for universal charity, and when they
ridicule sympathy as a weakness of character or an ethical blunder
of Christianity. It is just in its insistence on sympathy that the
Christian teaching is most valuable, and this part of its system
will survive long after its dogmas have sunk into oblivion. However,
this lofty duty must not be confined to men, but extended to "our
relations," the higher vertebrates, and, in fact, to all animals whose
brain-organization seems to point to the possession of sensation and
a consciousness of pleasure and pain. Thus, for instance, in the case
of the domestic animals which we use daily in our service, and which
have an undoubted psychic affinity to ourselves, we must take care
to increase their pleasures and mitigate their sufferings. Faithful
dogs and noble horses, with which we have lived for years and which
we love, are rightly put to death and relieved from pain when they
fall hopelessly ill in old age. In the same way we have the right, if
not the duty, to put an end to the sufferings of our fellow-men. Some
severe and incurable disease makes life unbearable for them, and they
ask for redemption from evil. However, medical men hold very different
opinions on the matter, as I have found in conversation with them.
Many experienced physicians, who practise their profession in a spirit
of sympathy and without dogmatic prejudice, have no scruple about
cutting short the sufferings of the incurable by a dose of morphia or
cyanide of potassium when they desire it; very often this painless
end is a blessing both to the invalids and their families. However,
other physicians and most jurists are of opinion that this act of
sympathy is not right, or is even a crime; that it is the duty of the
physician to maintain the life of his patients as long as he can in all
circumstances. I should like to know why.

While I am dealing with this important and--for the medical
conscience--difficult question of social ethics, I may take the
opportunity to consider the general attitude of physicians to the
monistic philosophy. It is now half a century since I visited the
wards in the Julius hospital at Würtzburg as a medical student. It is
true that--happily for me and my patients!--I practised the profession
only for a short time after I had passed my examinations in 1857;
but the thorough acquaintance with the human organism, its anatomic
structure and physiological functions, which I then obtained has been
of incalculable service to me. I owe to it not only the solid empirical
foundation of the special study of my life, zoology, but also the
monistic tendency of my whole system. As the medical training in its
widest sense includes anthropology--and so should include psychology
also--its value for speculative philosophy cannot be exaggerated. The
scholastic metaphysicians who still regard the chairs of philosophy at
our universities as their monopoly would have avoided most of their
dualistic errors if they had had a thorough training in human anatomy,
physiology, ontogeny, and phylogeny. Even pathology, the science of
the diseased organism, is very instructive for the philosopher. The
psychologist especially acquires, by the study of mental disease and
the visiting of the asylum wards, a profound insight into the mental
life which no speculative philosophy could give him. There are few
experienced and thoughtful physicians who retain the conventional
belief in the immortality of the soul and God. What would the immortal
soul do on the other side of eternity when it is already utterly
ruined in this life, or was even born as an idiot? How can a just God
condemn the criminal to the fires of hell when he himself has tainted
the man with an hereditary bias, or has placed him in an environment
in which, seeing the absence of free-will, crime was a necessity for
him? And how can this all-loving God answer for the immeasurable sum of
want and misery, and pain and unhappiness, which he sees accumulated
before him every year in the lives of families and states, cities and
hospitals? It is no wonder that the old saying ran: _Ubi tres medici,
duo sunt athei_ (Of three doctors two are sure to be atheists). One
of my medical colleagues was an old, experienced, and sympathetic
physician who had travelled all over the world, and had then, as
director of a large hospital, been a close witness of the sufferings of
humanity. Religiously educated by pious parents, and endowed with keen
sensitiveness, he was, after long struggles, forced by his medical
studies to part with the faith of his boyhood--like myself, in his
twenty-first year. We were talking about the great mysteries of life
shortly before his death, and he said to me: "I have been unable to
reconcile belief in the immortality of the soul and the freedom of the
will with my psychological experiences, and I have been just as unable
to discover throughout the whole world a single trace of a moral order
or a beneficent providence. If it is true that an intelligent Deity
rules the world, he cannot be a God of love, but an all-powerful demon,
whose constant entertainment is an eternal and merciless play of being
and becoming, building up and destroying." However, we do still find
here and there informed and intelligent physicians who adhere to the
three central dogmas of metaphysics--a proof of the immense power of
dogmatic tradition and religious prejudice.

We must class as a traditional dogma the wide-spread belief that
man is bound under all circumstances to maintain and prolong life,
even when it has become utterly useless--a source of pain to the
incurable and of endless trouble to his friends. Hundreds of thousands
of incurables--lunatics, lepers, people with cancer, etc.--are
artificially kept alive in our modern communities, and their sufferings
are carefully prolonged, without the slightest profit to themselves or
the general body. We have a strong proof of this in the statistics of
lunacy and the growth of asylums and nerve-sanatoria. In Prussia alone
there were 51,048 lunatics cared for in the asylums (six thousand in
Berlin) in 1890; more than one-tenth of them were quite incurable (four
thousand of them suffering from paralysis). In France, in 1871, there
were 49,589 in the asylums (or 13.8 per thousand of the population),
and in 1888 there were 70,443 (or 18.2 per thousand); thus, in the
course of seventeen years, the absolute number of the unsound rose
nearly 30 per cent. (29.6), while the total population only increased
5.6 per cent. In our day the number of lunatics in civilized countries
is, on the average, five-sixths per thousand. If the total population
of Europe is put at three hundred and ninety to four hundred millions,
we have at least two million lunatics among them, and of these more
than two hundred thousand are incurable. What an enormous mass of
suffering these figures indicate for the invalids themselves, and what
a vast amount of trouble and sorrow for their families, what a huge
private and public expenditure! How much of this pain and expense could
be spared if people could make up their minds to free the incurable
from their indescribable torments by a dose of morphia! Naturally
this act of kindness should not be left to the discretion of an
individual physician, but be determined by a commission of competent
and conscientious medical men. So, in the case of other incurables
and great sufferers (from cancer, for instance), the "redemption from
evil" should only be accomplished by a dose of some painless and rapid
poison when they have expressed a deliberate wish (to be afterwards
juridically proved) for this, and under the control of an authoritative
commission.

The ancient Spartans owed a good deal of their famous bravery, their
bodily strength and beauty, as well as their mental energy and
capacity, to the old custom of doing away with new-born children who
were born weakly or crippled. We find the same custom to-day among
many savage races. When I pointed out the advantages of this Spartan
selection for the improvement of the race in 1868 (chapter vii. of
the _History of Creation_) there was a storm of pious indignation in
the religious journals, as always happens when pure reason ventures
to oppose the current prejudices and traditional beliefs. But I ask:
What good does it do to humanity to maintain artificially and rear the
thousands of cripples, deaf-mutes, idiots, etc., who are born every
year with an hereditary burden of incurable disease? Is it not better
and more rational to cut off from the first this unavoidable misery
which their poor lives will bring to themselves and their families? It
is no use to reply that religion forbids it. Christianity also bids us
give up our life for our brethren, and to cast it from us when it hurts
us--that is to say, when it only causes useless pain to us and our
friends. The truth is, the opposition is only due to sentiment and the
power of conventional morality--that is to say, to the hereditary bias
which is clothed in early youth with the mantle of religion, however
irrational and superstitious be its foundation. Pious morality of this
sort is often really the deepest immorality. "Laws and rights creep on
like an eternal sickness;" this is equally true of the social customs
and morals on which laws and rights are founded. Sentiment should
never be allowed to usurp the place of reason in these weighty ethical
questions. As I pointed out in the first chapter of the _Riddle_,
sentiment is a very amiable, but a very dangerous, function of the
brain. It has no more to do with the attainment of the truth than what
is called revelation. That is well seen in Kant's dualism, for his
_mundus intelligibilis_ is essentially an outcome of his religious
sentimentality




VI

PLASM

 Plasm is the universal living substance--Definition of protoplasm,
 chemically and morphologically--Physical character--Viscous
 condition--Chemical analysis--Colloid character of
 albumin--Albuminoid molecules--Elementary structure of plasm--Work
 of plasm--Protoplasm and metaplasm--Structures of metaplasm--Frothy
 structure--Skeletal structure--Fibrous structure--Granular
 structure--Molecular structure--Plasma molecules--Plastidules and
 biogens--Micella and biophora--Caryoplasm and cytoplasm--Nuclear
 matter--Chromatin and achromin--Nucleolus and centrosoma--Caryotheka
 and caryolymph--Cellular matter--Plasma products--Internal plasma
 products--External plasma products--Cell membranes--Intercellular
 matter--Cuticular matter.


By plasm, in the widest sense of the word, we mean the living matter,
or all bodies that are found to constitute the material foundations
of the phenomena of life. It is usual to give this matter the name
of protoplasm; but this older and historically important designation
has suffered so many changes of meaning through the variety of its
applications that it is better now to use it only in the narrower
sense. Moreover, recent research on protoplasm has been greatly
developed, and several new names have been invented, which are formed
from the word "plasm" with a qualifying prefix. These are special
varieties of the general idea of plasm, or special modifications of the
general matter, such as metaplasm, archiplasm, and so on.

The botanist, Hugo Mohl, who first introduced the name "protoplasm"
in 1846, used it to designate a part of the contents of the ordinary
plant-cell--namely, the viscous matter that Schleiden called
"cell-mucus," which is found on the inner surface of the cell-wall,
and often forms a varying net-work or skeleton in the watery fluid in
the cell, and exhibits characteristic movements. Mohl gave the name of
"primordial skin" to this important wall-layer (the chief element of
the plant-cell), and called the material of it, as being chemically
different from the other parts of the cell, _protoplasm_--that is to
say, the first (_proton_) or earliest formation of the organism. It is
important to notice that Mohl, the author of the name, conceived it in
a purely chemical, not a morphological, sense, like Oscar Hertwig and
other recent cytologists. I intend to retain this early chemical idea
of protoplasm--or, briefly, plasm. It was also taken in this sense by
Max Schultze, who pointed out (in 1860) its extreme significance and
wide distribution in all living cells, and introduced an important
reform of the cell-theory which we will see later.

The mixing of the chemical and the morphological ideas of protoplasm
has been very mischievous in recent biology, and has led to great
confusion. It generally comes from a failure to formulate clearly the
difference between the two essential elements of the modern notion of
the cell--the anatomic distinction between the nucleus and the body
of the cell. The internal nucleus (or _caryon_) had the appearance of
a solid, definite, morphologically distinct constituent of the cell;
the outer and softer mass which we now call the cell-body (_celleus_
or _cytosoma_) seemed to be a formless and only chemically definable
protoplasm. It was only discovered at a later date that the chemical
composition of the nucleus is closely akin to that of the cell-body,
and that we may properly associate the _caryoplasm_ of the one with the
_cytoplasm_ of the other under the general heading of _plasm_. All the
other materials that we find in the living organism are products or
derivatives of the active plasm.

In view of the extraordinary significance which we must assign to the
plasm--as the universal vehicle of all the vital phenomena (or "the
physical basis of life," as Huxley said)--it is very important to
understand clearly all its properties, especially the chemical ones.
This is rendered somewhat difficult from the circumstance that the
plasm is, in most of the organic cells, closely bound up with other
substances--the various plasma products; it can rarely be isolated in
its purity, and can never be had pure in any quantity. Hence we are for
the most part dependent on the imperfect, and often ambiguous, results
of microscopic and microchemical research.

In every case where we have with great difficulty succeeded in
examining the plasm as far as possible and separating it from the
plasma-products, it has the appearance of a colorless, viscous
substance, the chief physical property of which is its peculiar
thickness and consistency. The physicist distinguishes three conditions
of inorganic matter--solid, fluid, and gaseous. Active living
protoplasm cannot strictly be described as either fluid or solid in the
physical sense. It presents an intermediate stage between the two which
is best described as viscous; it is best compared to a cold jelly or
solution of glue. Just as we find the latter substance in all stages
between the solid and the fluid, so we find in the case of protoplasm.
The cause of this softness is the quantity of water contained in the
living matter, which generally amounts to a half of its volume and
weight. The water is distributed between the plasma molecules, or the
ultimate particles of living matter, in much the same way as it is in
the crystals of salts, but with the important difference that it is
very variable in quantity in the plasm. On this depends the capacity
for absorption or imbibition in the plasm, and the mobility of its
molecules, which is very important for the performance of the vital
actions. However, this capacity of absorption has definite limits
in each variety of plasm; living plasm is not soluble in water, but
absolutely resists the penetration of any water beyond this limit.

The chemistry of living matter is the most important and interesting,
but at the same time the most difficult and obscure, part of the whole
of biological chemistry. In spite of the innumerable and careful
investigations which have been made of it by the ablest physiologists
and chemists in the second half of the nineteenth century, we are
still far from a satisfactory solution of this fundamental problem
of biology. This is due partly to the extraordinary difficulty of
isolating pure living plasm and subjecting it to chemical analysis,
and partly to the many errors and misunderstandings that have arisen
through one-sided treatment of the subject, and especially through
confusion of the chemical and morphological features of plasm. We can
thus understand the contradictory views that are still put forward by
distinguished chemists and physiologists, zoologists and botanists.
As I cannot deal here with the very extensive, elaborate, and
contradictory literature of the subject, I must be content to give a
brief summary of the conclusions I have reached by my reading and my
own studies of plasm (begun in 1859).

To begin with, we must clearly understand that protoplasm--in the most
general sense in which we here take it--is a _chemical_ substance, not
a "mixture of different substances," or a "mixture of a small quantity
of solid matter with a good deal of fluid." As Richard Neumeister
very well observes: "We seek the nature of protoplasm in the peculiar
processes which take place in its constituent matter. Protoplasm is
for us a chemical matter, so pronounced, in fact, that the highest
chemical actions that we know of are embodied in it." I must, from my
point of view, entirely reject Oscar Hertwig's conception of living
matter as a "mixture" of a number of chemical elements; because
chemistry applies this phrase to various gases and powdery substances
which are completely indifferent to each other--a property which we
certainly do not find in the constituents of protoplasm. When we speak
of the living matter or protoplasm, the general phrase does not imply
that the substance may not have a distinctive composition in each
particular case. And when we find many biologists still conceiving
protoplasm as a mixture of various substances, the error is generally
due to a confusion of the chemical idea with the morphological, and to
a belief that certain structural features of the plasm are primary,
whereas they are only secondary, products of the vital process itself
in the cell-body.

The older biologists who first introduced the name protoplasm and
studied it carefully recognized that this living matter belonged
to the albuminous (or proteid) group. The many characteristics
which distinguish these nitrogenous carbon-compounds from all
other chemical compounds--their behavior towards acids and bases,
their peculiar color-reaction towards certain salts, their
decomposition-products, etc.--are found in all the plasma-substances,
and in all the other albuminoids. This is quite in agreement with
the results of quantitative analysis. However differently the
various plasma-substances behave in detail, they always exhibit the
same general composition as the other albuminoids out of the five
"organogenetic elements"--namely, in point of weight, fifty-one to
fifty-four per cent. carbon, twenty-one to twenty-three per cent.
oxygen, fifteen to seventeen per cent. nitrogen, six to seven per
cent. hydrogen, and one to two per cent. sulphur. However, there is
a good deal of variety and complication in the way in which the atoms
of these five elements are combined in albumin and their molecules
are grouped. Hence the question of the chemical nature of the
plasma-substances compels us now to look for a moment at the larger
group of albuminoids to which they belong.

The carbon-compounds which we comprise under the chemical title of the
albumins or proteids are the most remarkable, but also, unfortunately,
the least known, of all bodies. The attempt to examine them closely
encounters extraordinary difficulties, greater than in any other group
of chemical compounds. Everybody is familiar with the appearance of
ordinary albumin, from the transparent viscous albumin that surrounds
the yolk in the hen's egg, and which becomes a white, opaque, and solid
mass when it is cooked. However, this special form of albumin, which we
can get so easily in any quantity from the eggs of birds and reptiles,
is only one of the innumerable kinds of albumin, or species of protein,
that are to be found in the bodies of the various animals and plants.
Chemists have hitherto tried in vain to master the chemical structure
of these obscure protein-compounds. They are only rarely to be found in
chemically pure form as crystals. As a rule, they are in the colloid
form, or uncrystallized jelly-like masses, which offer a much greater
resistance than crystals to the passage through a porous medium by
diosmosis (see p. 39). However, although we have not yet succeeded in
penetrating the molecular constitution of the albumins, the laborious
research of chemists has yielded some general results which are of
great importance for our purpose. We have, in the first place, a
general idea of their molecular constitution.

Molecules are the smallest homogeneous parts into which a body can be
divided without altering its chemical character. Hence the molecules of
every chemical compound are made up of two or more atoms of different
kinds. The greater the number of atoms in each compound, the higher
is its molecular weight. The space between the molecules and their
component atoms is filled with imponderable and highly elastic ether.
As even the largest molecules occupy only a very tiny space, and
remain far below the range of the most powerful microscope, all our
ideas of their composition depend on general physical theories and
special chemical hypotheses. Nevertheless, stereochemistry, the modern
science of the molecular structure of chemical compounds, is not only
a perfectly legitimate section of natural philosophy, but it yields
the most important conclusions as to the mutual attractions of the
elements and the invisible movements of the atoms in combining. It
further enables us to calculate approximately the relative size of the
molecules and the number of atoms that are grouped together in them.
However, the albuminoids present the greatest difficulty of all in this
calculation, and their structural features are still very obscure.
Nevertheless, science has reached certain general conclusions, which we
may formulate in the following propositions:

1. The molecule of albumin is unusually large, and therefore its
molecular weight is very high (higher than in most or all other
compounds).

2. The number of atoms composing it is very large (probably much more
than a thousand).

3. The disposition of the atoms and groups of atoms in the albuminous
molecule is very complicated, and at the same time very unstable--that
is to say, very changeable and easily altered.

These characters, which are ascribed to all albuminous bodies by
modern chemistry, hold good of all plasma-substances; and, in fact,
are true in a higher degree of these, as the metabolism of the living
matter causes a constant displacement of the atoms. This is caused,
according to the view of Franz Hofmeister and others, by the formation
of ferments or enzyma--in other words, by catalysators of a colloidal
structure. Verworn has, on physiological grounds, given the name of
biogens to these plasma-molecules.

The profound insight which comparative anatomy has given us into the
significance and nature of organs, and comparative histology into
those of the cells, has naturally excited a desire to penetrate in the
same way the mystery of the elementary structure of the plasm, the
chief active constituent of the cell. The improved methods of modern
cytology, and the great progress which this science of the cell owes
to the microtome and to microchemistry with its delicate coloring
processes, etc., have prompted many observers of the last three decades
to study the finest structural features of the elementary organism,
and on this foundation build hypotheses as to the elementary structure
of protoplasm. In my opinion, all these theoretical ideas, in so far
as they would explain the finer structure of pure plasm, have a very
serious defect; they relate to microscopic structures which do not
belong to the plasm as such (as a chemical body), but to the cell-body
(or cytosoma), the chief active constituent of which is certainly the
plasm. These microscopic structures are not the efficient causes of
the life-process, but products of it. They are phylogenetic outcomes
of the manifold differentiations which the originally homogeneous and
structureless plasm has undergone in the course of many millions of
years. Hence I regard all these "plasma-structures" (the comb, threads,
granules, etc.), not as original and primary, but as acquired and
secondary. In so far as these structures affect the plasm as such, it
must take the name of metaplasm, or a differentiated plasm, modified
by the life-process itself. The true protoplasm, or viscous and at
first chemically homogeneous substance, cannot, in my opinion, have any
anatomic structure. We shall see, when we come to consider the monera,
that very simple specimens of such organisms without organs still
actually exist.

By far the greater part of the plasm that comes under investigation as
active living matter in organisms is metaplasm, or secondary plasm,
the originally homogeneous substance of which has acquired definite
structures by phyletic differentiations in the course of millions
of years. To this modified plasm we must oppose the original simple
primary plasm, from the modification of which it has arisen. The name
"protoplasm," in the narrower sense, could very properly be retained
for this originally homogeneous form of structureless plasm; but, as
the term has now almost lost definite meaning and is used in many
different senses, it is, perhaps, better to call this pure homogeneous
primary plasm _archiplasm_. It is still found--firstly, in the body of
many (but not all) of the monera, part of the chromacea and bacteria,
and the protamœba and protogenes; and, secondly, in the body of many
very young protists and tissue-cells. In the latter case, however,
there is already a chemical differentiation of the inner caryoplasm and
outer cytoplasm. When we examine these young cells under a high power
of the microscope, with the aid of the modern coloring methods, their
protoplasm seems to be perfectly homogeneous and structureless, or, at
the most, there are merely very fine granules regularly distributed in
it which are believed to be products of metabolism. This is best seen
in many of the rhizopods, especially the amœbæ, thalamophora, and
mycetozoa. There are large amœbæ, which thrust out strongly mobile
feet from their unicellular body, broad, flaplike processes of the
naked cell body which constantly change their form, size, and place.
If they are killed and examined with the aid of the best methods of
coloring, it is quite impossible to detect any structure in them; and
this is also true of the pseudopodia of the mycetozoa and many other
rhizopods. Moreover, the slow flowing movement of the fluid protoplasm
shows clearly that there cannot be any composition out of fine fixed
elements in the body. This is particularly clear in those amœbæ
and mycetozoa in which a hyaline, firm, and non-granulated skin-layer
(hyaloplasm) is more or less separated from a dark, softer, and
granulated marrow-layer (polioplasm); as both of them are viscous and
pass into each other without sharp limits, there cannot be any constant
and fixed structural features in them.

Organic life--in its lowest and simplest form--is nothing but a form
of metabolism, and therefore a purely chemical process. The whole
vital activity of the chromacea, the simplest and oldest organisms
that we know, is confined to that process of metabolism which we
call plasmodomism or carbon-assimilation. The homogeneous and
structureless globules of protoplasm, which represent the whole frame
of these primitive protophyta (chroococcus, aphanocapsa, etc.) in
the simplest conceivable way, expend their whole vital power in the
process of self-maintenance. They maintain their individuality by a
simple metabolism; they grow by the addition of fresh plasm obtained
by it, and they split up into two equal globules of plasm when the
growth passes a certain limit--reproduction by clevage, maintenance
of the species. Thus these chromacea have neither special organs, or
organella, that we can distinguish in their simple plasma-bodies, nor
different functions in their life-process; it is wholly taken up with
the primitive work of their vegetal metabolism. We shall see later
on that this is a purely chemical process, something like catalysis
in inorganic combinations; and for this neither special organs nor
fine elementary structures in the plasm are needed. The "end" of their
existence, self-maintenance, is attained just as simply as in the
catalysis of any inorganic compound, or the formation of a crystal in
its mother-water.

If we compare this very rudimentary life-process of the monera with
that of the highly differentiated protists (diatomes, desmidiacea,
radiolaria, and infusoria), the biological distance between them seems
to be immense; and it is, naturally, far greater when we extend the
comparison to the histona, the highly organized metaphyta and metazoa,
in the bodies of which millions of cells co-operate in the work of the
various tissues and organs.

In the great majority of cells--either the autonomous cells of the
protists or the tissue-cells of the histona--we can detect more or less
definite and constant fine structures in the plasm. We must regard
these always as phyletic, secondary products of the life-process,
and so call the differentiated plasm by the name of metaplasm. The
very different interpretations of the microscopic pictures which this
metaplasm affords have led to a good deal of controversy. In this the
desire to discover in these secondary plasma-structures the first
causes of vital action, or the real elementary organella of the cell,
has played a great part. The most important of the theories that
have been formulated are those of the frothy structure, the skeletal
structure, the fibrous structure, and the granulated structure of the
plasm. All these theories of structure apply to plasm in general, but
particularly to its two chief forms, the caryoplasm of the nucleus and
the cytoplasm of the cell-body.

Among the many different attempts to discover a definite structure in
living matter, the theory of the frothy structure (also called the
honeycomb structure) has lately found the most favor. Otto Bütschli,
of Heidelberg, especially, has endeavored, on the basis of many years
of careful study and experiment, to make it the foundation of his
view of the plasm. It is undeniable that the living matter of many
cells shows a delicate structure which may best be compared with
fine soap-suds; innumerable globules are crowded close together in
a fluid, and flatten each other by their pressure into polyhedrical
shapes. In 1892 Bütschli artificially produced fine oil-suds by
beating up cane sugar or potash in olive oil, and then put a small
drop of the stuff in a drop of water under the microscope. The small
particles of sugar then exercised an attractive action by diffusion on
the particles of water; the latter penetrated into the oily matter,
released the sugar, and formed tiny vesicles with it. As the vesicles
of sugar do not mix with oil, they look like cavities isolated on
all sides, and polyhedrically flattened by mutual pressure. The
striking resemblance of this artificially produced "oil soap-suds" to
the natural and microscopically visible structures of many kinds of
plasm is strengthened from the fact that Bütschli, Georg Quincke, and
others, have also observed similar flowing movements in both; and as
these apparently spontaneous movements can be explained physically and
reduced to adhesion, imbibition, and other mechanical causes, there
seemed a prospect of reducing the "vital" movements of the living
and flowing plasm to purely physical forces. Quite recently Ludwig
Rhumbler, of Göttingen, an authority on the rhizopods, has endeavored
to give in this sense a _Physical analysis of the vital phenomena
in the cell_. To-day the froth theory is much the most popular of
the many attempts to detect a fine plasm-structure as the essential
anatomic foundation of an explanation of the physiological functions.
It must be noted, however, that frequently very different phenomena
are confused under this name, especially the coarser froth-formation
by taking up water in the living matter and the invisible hypothetical
molecular structure. Both these must be distinguished from the finer
plasma-structure which is visible under a powerful microscope; but the
limit between them is difficult to determine.

A second view of the finer structure of the plasm, which had been
greatly esteemed before the acceptance of the froth theory, was
formulated in 1875 by Carl Frommann and Carl Heitzmann, and supported
by Leydig, Schwitz, and others. It puts another interpretation on the
net-like appearance of the microscopic plasma-structure. It assumes
that the plasma consists of a skeleton of fine threads or fibrils
combined in the form of a net, and that these spread and cross in the
body of the cell which is filled with fluid. It is also compared to a
sponge, and is said to have a spongy structure. We can artificially
produce such a skeletal structure by, for instance, causing coagulation
in a thick solution of glue or albumin by adding alcohol or chromic
acid. It is unquestionable that there are these "plasma-skeletons" both
in the nucleus and the body of the cell; but they are generally (if not
always) secondary products of organization in the elementary organism
(or cell-organs), not primitive structures of its plasm. Moreover, an
optical transverse action of a froth-structure or honeycomb, examined
as a flat surface in the microscope, shows the same configuration as
a fine skeleton. We can hardly see any difference between the two. We
cannot accept the skeletal formation as a fundamental structure of the
plasm.

As we notice very fine threads in the plasm of many cells, both in
the caryoplasm of the nucleus and the cytoplasm of the cell body,
the cytologist Flemming, of Kiel (1882), believed it was possible to
discover them in the plasm of all cells, and based on this his filar
theory of plasm. He says that we must distinguish two chemically
different kinds of plasm in living matter--the filar (threadlike) and
the inter-filar matter. The fine threads of the former are of different
lengths, and sometimes run separately, at other times are bound in a
sort of net-work (_mitoma_ and _paramitoma_). In certain conditions of
cell-life, especially in indirect cell-division, these filar formations
play a great part; and also in the functions of highly differentiated
cells, such as the ganglionic cells. But in many cases these plasma
threads may be merely parts of a skeletal or frothy structure
(honeycomb walls in section). In any case, we cannot regard the thread
formation as a general elementary structure of plasm; in my opinion, it
is always a secondary phyletic product of living matter, and never a
primary feature of it.

Totally different from the three preceding theories of the finer
structure of the plasm is the granular theory of Altmann (1890). He
supposes that all living matter is originally made up of tiny round
granules, and that these independently living _bioblasts_ are the real
"elementary organisms," the microscopic ultimate individuals; hence
the cells which are formed by the combination of these granules must
be looked on as individuals of the second order. Between the granules
of the granulated substance (the real active living matter) there
is always an inter-granular substance; the granules are regularly
distributed and arranged in these. The granules themselves, or the
bioblasts, are homogeneous, sometimes globular, and sometimes oval,
or of other shapes. However, the distinction between these substances
is quite arbitrary, and neither chemically nor morphologically well
defined. Under the head of granules Altmann throws together the most
different contents of the cell--fat granules, pigment granules,
secretory granules, and other products of metabolism. Hence his
granular theory is now generally rejected. However, there was a
sound idea at the bottom of it--namely, the idea of explaining the
vital properties and functions of living matter by small separate
constituents which make up the plasm, and move in a viscous medium.
But these real elementary parts are not microscopically visible;
they belong to the molecular world, which lies far below the limit
of microscopic power. In my opinion, Altmann's visible granules,
like Flemming's threads and Frommann's skeleton and Bütschli's
honeycomb, are not primary structures, but secondary products of plasma
differentiation.

As the special properties and activities of any natural body depend on
its chemical constitution, and this is, in the long-run, determined
by the composition of its molecules, it is a matter of the greatest
interest in biology to form as clear and distinct an idea as possible
of the nature and properties of the molecules of plasm. Unfortunately,
it is only possible to do this approximately, and to a slight extent.
As the hypotheses of modern structural chemistry on the molecular
formation of complicated organic compounds are often very unsafe,
this is bound to be the case in the highest degree as regards the
albuminoids and, the most important of all, the living matter or plasm.
We have as yet no knowledge of the fundamental features of its very
variable chemical structure. The one thing that bio-chemists have told
us about it is that the molecule of plasm is very large, and made up of
a great number of atoms (over a thousand); and that these are combined
in smaller or larger groups, and are in a state of very unstable
equilibrium, so that the life process itself causes constant changes in
them.

Since the great problem of heredity was forced by Darwin in 1859
into the foreground of general biology, many different hypotheses
and theories of it have been framed. All these have in the end to
trace it to molecular features in the plasm of the germ-cells;
because it is this germ-plasm of the maternal ovum and the paternal
sperm-cell that conveys the characteristics of the parents to the
child. Hence the great progress that has been made recently in the
study of conception and heredity, by means of a number of remarkable
observations and experiments, has been of service to our ideas on
the molecular structure of the plasm. I have dealt with the chief of
these theories in the ninth chapter of my _History of Creation_, and
must refer the reader thereto. In chronological order we have: (1)
the pangenesis theory of Darwin (1868), (2) the perigenesis theory of
Haeckel (1875), (3) the idioplasm theory of Nägeli (1884), (4) the
germ-plasm theory of Weismann (1885), and (5) the mutation-theory of De
Bries (1889). None of these attempts, and none of the later theories
of heredity, has given us a satisfactory and generally admitted idea
of the plasma-structure. We are not even clear as to whether in the
last resort life is to be traced to the several molecules, or to groups
of molecules, in the plasm. With an eye to this latter difference, we
may distinguish the plastidule and micellar theories as two different
groups of relevant hypotheses.

In my essay on "The Perigenesis of the Plastidules" (1875) I formulated
the hypothesis that in the last instance the plastidules are the
vehicles of heredity--that is to say, plasma-molecules which have the
property of _memory_. In this I found support in the ingenious theory
of the distinguished physiologist, Ewald Hering, who had declared in
1870 that "memory is a general property of organic matter." I do not
see still how heredity can be explained without this assumption! The
very word "reproduction," which is common to both processes, expresses
the common character of psychic memory (as a function of the brain). By
plastidules I understand simple molecules; the homogeneous nature of
the plasm in the monera (both chromacea and bacteria and rhizomonera)
and the primitive simplicity of their life-functions do not dispose
us to think that special groups of molecules are to be distinguished
in these cases. Max Verworn has recently (1903) formulated his
biogen-hypothesis in the same sense, as a "critical-experimental study
of the processes in the living matter." He also takes the active
plasma-molecules, which he calls biogens, as the ultimate individual
factors of the life-process, and is convinced that in the simplest
cases the plasm consists of homogeneous biogen-molecules.

The hypothesis of Nägeli (1884) and Weismann (1885) is totally
different from the hypothesis of the plastidules and biogens as
simple molecules of the plasm. According to this, the ultimate "vital
unities" or individual vehicles of the life-process are not homogeneous
plasma-molecules, but groups of molecules, made up of a number of
different molecules. Nägeli calls them _micella_, and assigns them a
crystalline structure. He supposes that these micella are combined
chainwise into micellar ropes, and that the variety of the many forms
and functions of plasm is due to the different configuration and
arrangement of these. Weismann says: "Life can only arise by a definite
combination of different kinds of molecules, and all living matter
must be made up of these groups of molecules. A single molecule cannot
live, can neither assimilate nor grow nor reproduce." I do not see
the justice of this observation. All the chemical and physiological
properties which Weismann afterwards attributes to his hypothetical
_biophora_ may be ascribed to a single molecule just as well as to
a group of molecules. In the simplest forms of the monera (both the
chromacea and the bacteria) the nature of their rudimentary life
can be explained on the one supposition just as well as the other.
Naturally, this does not exclude a very complicated chemical structure
in the large plastidule or biogen as a single molecule. Verworn's
biogen-hypothesis seems to me quite satisfactory when it represents the
primitive molecule of living matter as really the ultimate factor of
life.

The chief process in the evolutionary history of the plasm is its
separation into the inner nuclear matter (caryoplasm) and the outer
cellular matter (cytoplasm). When both kinds of plasm arose by
differentiation from the originally simple plasm of the monera, there
also took place the morphological separation of the nucleus (caryon)
and cell-body (cytosoma or celleus). As these two chief forms of living
matter are chemically different but nearly related, and as they may
in certain circumstances (for instance, during indirect cell-division
and the partial caryolysis connected therewith) enter into the closest
mutual relations, we must suppose that the original severance of the
two substances took place gradually and during a long period of time.
It was not by a sudden bound or transformation, but by a gradual
and progressive formation of the chemical antithesis of caryoplasm
and cytoplasm, that the real nucleated cell (cytos) arose from the
unnucleated cytode (or primitive cell). Both may correctly be comprised
under the general head of _plastids_ (or formative principles), as
"ultimate individualities."

I regard as the chief cause of this important differentiation of the
plasm the accumulation of hereditary matter--that is to say, of the
internal characteristics of the plastids acquired by ancestors and
transmitted to their descendants--within the plastids while their
outer portion continued to maintain the intercourse with the outer
world. In this way the inner nucleus became the organ of heredity
and reproduction, and the outer cell-body the organ of adaptation
and nutrition. I put forward this hypothesis in 1866 in my _General
Morphology:_ "The two functions of heredity and adaptation seem to
be not yet distributed between differentiated substances in the
unnucleated cytodes, but to inhere in the whole of the homogeneous mass
of the plasm; while in the nucleated cell they are divided between
the two active constituents of the cell, the inner nucleus taking
over the transmission of hereditary characters and the outer plasm
undertaking adaptation, or the accommodation to the features of the
environment." This hypothesis was afterwards (1873) confirmed by the
discoveries of Strasburger, the brothers Hertwig, and others, with
regard to cell-cleavage and fertilization; it is particularly supported
by the phenomena of _caryokinesis_(the movement of the nucleus) in
sexual generation. Hence we can understand how it is that in the monera
(chromacea and bacteria), which propagate by simple cleavage, there is
no sexual generation and no nucleus.

The great significance of the nucleus in the life of the cell, as
central organ of heredity, and also probably as "the soul of the
cell," depends chiefly on the chemical properties of its albuminous
matter, the caryoplasm. This one indispensable nuclear element is
chemically akin to the cytoplasm of the cell-body, but differs from it
in certain respects. The caryoplasm has a greater affinity for many
coloring matters (carmine, hæmatoxylin, etc.) than the cytoplasm; and
the former coagulates more quickly and firmly than the latter through
acids (such as acetic and chromic acid). Hence we need only add a drop
of diluted (two per cent.) acetic acid to cells that seem homogeneous
to make perfectly clear the separation between the inner nucleus and
outer body. As a rule, the firmer nucleus then stands out sharply as
a globular or oval particle of plasm; occasionally it has other forms
(cylindrical, conical, spiral, or branched). The caryoplasm seems
to be originally quite homogeneous and structureless, as we find
in many of the protists and many young cells of histona (especially
young embryos). But in the great majority of cells the caryoplasm is
divided into two or more different substances, the chief of them being
chromatin and achromin.

The most common division of the caryoplasm in the cells of the animal
and plant body, and the one of chief significance for their vital
activity, is that into two chemically different substances, which
are usually called chromatin (or nuclein) and achromin (or linin).
Chromatin has a greater affinity for coloring (_chromos_) matter
(carmine, hæmatoxylin, etc.), and so this "colorable nuclear matter"
is particularly regarded as the vehicle of heredity. The achromin (or
achromatin, or linin) is either not at all or less easily colorable,
and is akin to the cytoplasm; in direct cell-division it enters into
close relations with the latter. Achromin is usually found in the
form of slender threads, and hence called "nuclear thread-matter"
(linin). Chromatin is generally found in roundish or rod-shaped
granules (chromosomata), which exhibit very characteristic changes of
form (loop formation, etc.) in indirect cell-division. The chemical,
physiological, and morphological difference between chromatin and
achromin must not be regarded as an original property of cell nuclei
(as is wrongly stated sometimes), but is the outcome of a very early
phylogenetic differentiation in the originally homogeneous caryoplasm;
and this holds also of two other parts of the nucleus--the nucleolus
and centrosoma.

In a good many cells, but by no means universally, we find two other
constituents of the nucleus, which owe their rise to a further
differentiation of the caryoplasm. The nucleolus is a small globular or
oval particle, which may be found singly or in numbers in the nucleus,
and behaves somewhat differently towards coloring matter than the
closely related chromatin. It has a special affinity for acid aniline
colors, gosin, etc. Its substance has, therefore, been distinguished
as _plastin_ or _paranuclein_. The nucleolus is especially found in
the tissue-cells of the higher animals and plants as an independent
constituent; it is wanting in many of the unicellular protists. The
same may be said of the centrosoma, or "central body" of the cell.
This is an extremely small granule, on the very limit of visibility,
the chemical composition of which is not known very well. We should
have paid no attention to this constituent of the cell (distinguished
in 1876) if it did not play an important, and perhaps leading, part
in indirect cell-division. As the "polar body in the division of
the nucleus," the centrosoma exercises a peculiar attraction on the
granules distributed in the cytoplasm, which arrange themselves
radially about this centre. The centrosomata grow independently and
increase by cleavage, like the chromoplasts (chlorophyll particles,
etc.). When they have split up, each of the daughter-microsomata acts
in turn as a centre of attraction on its half of the cell. However, the
great importance which modern cytologists have ascribed to it on this
account is discounted by two circumstances. In the first place, we have
not succeeded, in spite of all efforts, in discovering a centrosoma in
the cells of the higher plants and many of the protists; and, in the
second place, a number of recent chemical experiments have succeeded in
producing centrosomata artificially (for instance, by the addition of
magnesium chloride) in the cytoplasm. Hence many cytologists regard the
centrosoma as a secondary product of differentiation in the cell-body,
not the nucleus.

Two other parts of the nucleus that we find very often, but by no means
universally, in the cells of the animal and plant body are the nuclear
membrane (caryotheca) and the nuclear sap (caryolymph). A large number
of cells--but not all--have the appearance of vesicles, having a thin
skin enclosing a liquid content, the nuclear sap. The achromin then
usually forms a frame-work of threads, with chromatin granules in its
meshes or knots, within this round vesicle. This very thin nuclear
membrane (often only visible as its contour) or caryotheca may be
regarded as the result of surface-strain (at the planes of contact of
caryoplasm and cytoplasm). The watery and usually clear and transparent
nuclear sap (caryolymph) is formed by imbibition of watery fluid (like
the frothy structure of the plasm in general). The separation of the
nuclear membrane and nuclear sap is not a primary property of the
nucleus, but is due to a secondary differentiation in the originally
homogeneous caryoplasm.

Like the caryoplasm of the nucleus, the cytoplasm of the cell-body is
originally a chemical modification of the simple and once homogeneous
plasm (the archiplasm). This is clearly shown by the comparative
biology of the protists, their unicellular organism presenting a much
greater variety of stages of cell-organization than the subordinate
tissue-cells in the bodies of the multicellular histona. However, in
the great majority of cells the cytoplasm is separated into several,
and frequently very numerous, parts, which have received diverse forms
and functions in the division of labor. We then see very conspicuously
the regularity of cell-organization, which is altogether wanting in
the simple homogeneous plasma granules of the monera. As this great
differentiation of the advanced elementary organism is incorrectly
generalized by some recent cytologists and described as a universal
feature of cells, it is necessary to insist explicitly that it is a
secondary phylogenetic development, and is altogether wanting in the
primitive organisms. The complexity of the physiological division
of labor and the accompanying morphological separation of parts is
extremely great in the cytoplasm. When we wish to arrange them in a
few large groups from a general point of view, we may distinguish the
active plasma-formations from the passive plasma-products; the former
are due to a chemical metamorphosis of the living plasm, the latter
lifeless excretions from it.

Under the head of plasm-formations, or products of differentiation
in the cytoplasm, we comprise all formations that are due to partial
metamorphosis of the living cell-body--not lifeless excretions from
it, but living parts of its substance, undertaking special functions,
and therefore chemically and morphologically differentiated from the
primary cytoplasm. One of the commonest differentiations of this
kind is the separation of the firm hyaline skin-layer (hyaloplasm)
from the softer granular marrow-layer (polioplasm); though the two
often pass into each other without clear limits. In most plant-cells
special granules of plasm, mostly globular or roundish, are developed,
called _trophoplasts_, and these undertake the work of metabolism.
To this class belong the amyloplasts, which produce starch (amylum),
the chloroplasts or chlorophyll-granules which form the green
matter (chlorophyll) in the leaf, and the chromoplasts which form
color-crystals of various sorts. In the cells of the higher animals the
myoplasts form the special contractile tissue of the muscles, and the
neuroplasts the psychic tissue of the nerve-matter. On the other hand,
the distinction between the body-plasm (somoplasma) and the germ-plasm
(germoplasma), which serves as the base of Weismann's untenable theory
of the germ-plasm (_cf._ chapter xvi.), is purely hypothetical and
without direct observation to support it.

The infinite variety of parts of the cell which arise as excretions
of the living active cytoplasm, and so must be regarded as lifeless
plasma-products, may be divided into two chief groups--internal and
external. The former are stored within the living cytoplasm, the
latter thrust out from it.

Internal plasma-products of common occurrence are the microsomata,
very small and opaque particles which are generally regarded as
products of metabolism. They consist sometimes of fat, sometimes of
derivatives of albumin, sometimes of other substances of which we do
not know the chemical composition. The same may be said of the large
and variously-colored pigment-granules, which are very common and
determine the color of tissues. Also very common in the cytoplasm are
large accumulations of fat in the shape of oil-globules, fat-crystals,
etc., besides other crystals of a very different sort, partly organic
crystals (for instance, albuminous crystals in the aleuron-granules
of plants), partly inorganic crystals (for instance, of oxalic-acid
salts in many plant-cells, of calcareous salts in many animal-cells).
The watery cell-sap (cytolymph) plays an important part in many of
the larger cells. It is formed by the accumulation of fluid in the
cytoplasm, and is found in its frothy structure. The large empty spaces
which it forms are called vacuoles, with very regularly disposed
alveoles. When the cell-sap gathers in great abundance within the cell,
we get the large vesicular cells which are found in the tissues of the
higher plants, the cartilages, etc.

As external excretions of the living cytoplasm that have acquired
some importance, especially as protective organs, in the majority of
cells, we have first of all the cell-membranes, the firm capsules or
protective skins which enclose the soft cell-body, like a snail in
its house. In the first period of the cell-theory (1838-1859) such an
integument was ascribed to all cells, and often regarded as their chief
constituent; but it was discovered afterwards that this protective
skin is altogether wanting in many (especially animal) cells, and that
it is not found in many when they are young, but grows subsequently.
We now distinguish between naked cells (gymnocytes) and covered cells
(thecocytes). As examples of naked cells we have the amœbæ, and many
of the infusoria, the spores of algæ, the spermatozoa, and many animal
tissue-cells.

The cell-covering (cytotheca) varies very much in size, shape,
composition, and chemical character, especially in the rhizopods
among the unicellular protists. The flint shells of the radiolaria
and diatomes, the chalky cells of the thalamophora and calcocytea,
the cellulose shells of the desmidiacea and syphonea, show the
extraordinary plasticity of the constructive cytoplasm (_cf._ chapter
viii.). Among the histona the tissue-plants are remarkable for the
infinite variety of shape and differentiation of their cellulose
capsules. The familiar properties of wood, cork, bast, the hard shells
of fruit, etc., are due to the manifold chemical modification and
morphological differentiation which the cellulose membrane undergoes in
the tissues of plants. This is less frequently seen in the tissues of
animals; but, on the other hand, the intercellular and the cuticular
matter play a greater part in these.

The intercellular matter, an important external plasma-product, is
formed by the social cells in the tissues of the histona thrusting
out in common firm protective membranes. These protective structures
are very common among communities of protists, in the form of masses
of jelly, in which a number of cells of the same kind are united;
such are the zooglœa of many of the bacteria and chromacea, the
common jelly-like envelope of the volvocina and many diatomes, and the
globular cell-communities of the polycyttaria (or social radiolaria).
The chief part is played by intercellular matter in the body of the
higher animals, in the form of mesenchyma-tissue; the connecting
tissue, cartilages, and bones owe their peculiar property to the
amount and quality of the intercellular matter that is deposited
between the social cells.

When the socially joined epidermic cells at the surface of the
tissue-body thrust forth in common a protective covering, we get the
cuticles, which are often thick and solid armor-plates. In many of
the metaphyta wax and flinty matter are deposited in the cellulose
cuticles. The strongest formation is found in the invertebrate animals,
where the cuticle often determines the whole shape and articulation,
as in the calcareous shells of mollusks (mussel-shells, snail-shells,
cockle-shells, etc.); and especially the coats of the articulata (the
crab's coat of mail, and the skins of spiders and insects).




VII

UNITIES OF LIFE

 Units of life--Simple and complex organisms--Morphological and
 physiological individuals--Morphonta and bionta--Stages of
 individuality: cell, person, stem--Actual and virtual bionta--Partial
 and genealogical bionta--Metaphysical individuals--Cells (elementary
 organisms)--Cell membranes--Unnucleated cells--Plastids (cytodes
 and cells)--Primitive cells and nucleated cells--Organella (cell
 organs)--Cell communities (cœnobia)--Tissues of histona--Systems
 of organs--Organic apparatus--Histonal individuals (sprouts and
 persons)--Articulation of the histona (metamerism)--Stems of the
 histona--Animal states.


The dissection of the body of the higher animal and plant into
its various organs soon prompted comparative anatomists to draw a
distinction between simple and complex organisms. Then, when the
cell-theory developed in the course of the last half-century, the
common anatomic groundwork of all living forms was recognized in
the cell; and the conception of the cell as the elementary organism
led to the further belief that our own frame, like that of all the
higher animals and plants, is a cell-state, composed of millions of
microscopic citizens, the individual cells, which work more or less
independently therein, and co-operate for the common purposes of the
entire community. This fundamental principle of the modern cell-theory
was applied with great success by Rudolph Virchow to the diseased
organism, and led to most important reforms in medicine. The cells are,
in his view, independent "life-unities or individual life-centres,"
and the unified life of the whole man is the combined result of the
work of his component cells. In this way the cells are the real
life-unities of the organism. Their individual independence is at once
seen in the permanently unicellular protists, of which several thousand
species are already known to us.

On the other hand, we find among the lower animals and the higher
plants a composition of homogeneous parts, which represents a higher
stage of life-unity. The tree is an individual, but it is made up of
a number of branches or individual sprouts, each of which consists
in like manner of an axial stem with leaves attached. If we detach
such a branch and plant it in the ground, it takes root and grows
into an independent plant. So the coral-stem is made up of a number
of individual animals or persons, each of which has its own stomach
and mouth with a crown of tentacles. Each several coral-individual is
equivalent to a single living polyp (actinia). Thus the stem (_cormus_)
is a higher unity, both in the animal and the plant world. Even the
herds of gregarious animals, the swarms of bees and ants, and the
communities of human beings, are similar unities; with the difference
that the individual persons or citizens are not physically connected,
but held together by common interests. We can, therefore, distinguish
three stages of organic individuality, one building upon the other--the
cell, the person (or sprout), and the stem or state (cormus). Each
higher unity represents an intimate union of lower individuals.
Morphologically, in relation to their anatomic structure, the latter
are independent; but physiologically, in respect of the life-unity of
the whole, they are subordinated to the former.

This relation is quite clear in the familiar examples I have quoted.
But there are other organisms in which this is not so, and where the
question of the real individuality is very difficult to answer.
Thus, fifty years ago, we came to recognize floating animal-stems in
the remarkable siphonophora, or social medusæ, which had hitherto
been regarded as individual animals, or medusæ with a multiplicity
of organs; further study proved that each of these apparent organs
is really a modified medusa, and the whole united structure a stem.
This example throws a good deal of light on the important question of
association and division of labor. The whole floating siphonophoron
is, physiologically considered (in respect of its vital activity), a
harmoniously organized animal with a number of different organs; but
from the morphological point of view (in respect of form and structure)
each dependent organ is really an independent medusa.

It is clear, from these few illustrations, that the question of
organic individuality is by no means so simple as it seems at first
sight, and that it receives different answers according as we look
at the form and structure (morphologically) or the vital and psychic
activity (physiologically). We must, therefore, distinguish at once
between morphological (_morphonta_) and physiological (_bionta_)
individuals. The tree and the siphonophoron are bionta, or individuals
of the highest order, made up of a number of similar branches or
persons, the social morphonta. But, when we further dissect the latter
anatomically into their various organs, and these again into their
microscopic elements, the cells, each branch or person seems to be a
bion, and their cells to be morphonta. Each multicellular organism is,
however, developed in the beginning from a single cell, the stem-cell
(cytula) or fertilized ovum; this is at once a morphon and a bion, a
simple individual both morphologically and physiologically. The whole
process of its development into a multicellular organism consists in a
repeated cleavage of the stem-cell, the resultant cells being joined
in a higher unity, and assuming different forms in consequence of the
division of work.

The complicated modern state, with its remarkable achievements, may be
regarded as the highest stage of individual perfection which is known
to us in organic nature. But we can only understand the structure of
this extremely complex "organism of the highest order," and its social
forms and functions, when we have a sociological knowledge of the
various classes that compose it, and the laws of their association and
division of labor; and when we have made an anthropological study of
the nature of the persons who have united, under the same laws, for the
formation of a community and are distributed in its various classes.
The familiar arrangement of these classes, and the settling of the rank
in the mass and the governing body, show us how this complex social
organism is built up step by step.

But we have to look in the same way on the cell-state, which is made
up from the separate individualities in human society or in the
kingdom of the tissue-animals, or the branches in the kingdom of the
tissue-plants. Their complex organism, composed of various organs and
tissues, can only be understood when we are acquainted with their
constituent elements, the cells, and the laws according to which these
elementary organisms unite to form cell-communities and tissues, and
are in turn modified in the divers organs in the division of labor. We
must, therefore, first establish the scale of the morphonta, and the
laws of their association and ergonomy, according to which the several
stages or conditions of morphological individuality build on each
other. Three such stages may be at once distinguished: (1) the cell
(or, more correctly, the plastid), (2) the person (animal) or branch
(vegetal), and (3) the stem or cormus. But we shall find that there
are further subordinate stages under each of these three. It is only
in the case of the protists that the morphological unity is bound up
with the physiological. In the case of the histona, the multicellular,
tissue-forming organisms, this is only so at the beginning of
individual existence (at the stage of the stem-cell). As soon as the
multicellular body arises from this cytula by repeated segmentation, it
is raised to the stage of a higher individuality, the cell-state.

Our own human frame is, in its mature condition, like that of all the
higher animals, a very complete cell-state, but a single cell at the
beginning of its existence. We speak of the life-unity of the former
as an actual bion, and that of the latter as a virtual bion; in other
words, the physiological individual or the life-unity has in the first
case reached the highest stage of individual development that pertains
to its species, while in the second case it remains at the lowest
stage of virtual formation, and has only the capacity of rising to
the higher stage. In the higher plants and animals only one cell of
the organism, or the two combined sexual cells (ovum and spermium),
are the potential bion which may develop into an actual one. There
are, however, exceptions. In the fresh-water polyp (hydra) and cognate
cnidaria each piece of the body-wall, in the bath-sponge (euspongia)
and similar sponges each piece of tissue, and in many plants (for
instance, marchantia among the crytogams and bryophyllum among the
phanerogams) each portion of a branch or leaf, has the power to develop
into a mature organism, and is, therefore, a virtual bion.

From these virtual bionta (parts of the body that may grow into whole
organisms) we must distinguish the partial bionta which have not this
property. These are separated parts of the body that live for a time
after being cut off from the whole organism, but then die off. Thus,
for instance, the heart of a tortoise beats for a long time after being
cut out. A flower that has been plucked may, if put in water, keep
fresh and alive for many days. In some highly organized cephalopods one
of the eight arms of the male develops into an independent body, swims
about, and accomplishes the fertilization of the female (_hectocotylus_
among the _argonauta_, _philonexis_, etc.). It was at first thought
to be an independent animal parasite. The same thing happens with
the remarkable foldlike dorsal appendages of a large naked snail
(_thetys_), which get detached and creep about. The body of many of
the lower animals may be cut in pieces and yet may live for weeks. The
life-properties of these partial bionta are important in view of the
general question of the nature of life and its apparent unity in most
of the higher organisms. As a fact, even here the cells and organs lead
their separate individual life, though they are subordinate to and
dependent on the whole.

It has been attempted to answer this question of organic individuality
in the sense of counting all organisms individuals which develop from
a single fertilized ovum. Thus, the Italian botanist Gallesio, in
1816, regarded all plants that arise by asexual generation (budding
or segmentation)--sprouts, branches, slips, bulbs, etc.--as merely
portions of a single individual that came from an egg (the seed).
So also Huxley, in 1855, considered the sum of all the animals that
have been produced by asexual propagation, but from a single sexually
generated animal, to be parts of one individual. In practice, however,
this principle is useless. We should have to say that the millions
of plant-lice which arise parthenogenetically from unfertilized
germ-cells, but are originally descended from one impregnated ovum,
are one single individual; so also all the weeping-willows in Europe,
because they all came from shoots of one single sexually-produced tree.

Many attempts have been made in the course of the nineteenth century
to give a generally satisfactory answer to this difficult question of
the content and connotation of the idea of the organic individual.
None of these has found general favor. I have compared and criticised
them in the third book of my _General Morphology_. I there paid
special attention to the views of Goethe, Alexander Braun, and Nägeli
among the botanists, and Johannes Müller, Leuckart, and Victor Carus
among the zoologists. When we consider the striking divergence of the
views of such distinguished scientists and thinkers on so important a
biological question, we can understand that opinions are still very
divided to-day. Hence we must not be too hard on the metaphysical
philosophers when--in complete ignorance of the real facts--they rear
the most extraordinary theories in their airy speculations on "the
principle of individuation". Compare, for instance, the opinions of the
school-men and those of recent thinkers such as Arthur Schopenhauer and
Edward Hartmann. As a rule, the psychological side of the problem--the
question of the individual soul--is very prominent, without much
attention being paid to its material substratum--the anatomic basis of
the organism. Many metaphysicians, who, in their one-sided anthropism,
make man here also the measure of all things, would assign personal
consciousness as the basis of the idea of individuality. It is obvious
that this is not a practicable test even for the higher animals, to
say nothing of the lower animals and plants. In these we have a far
greater variety of individuality on the one hand, and a far greater
simplicity of construction on the other. I have tried to show, in my
essay on "The Individuality of the Animal Body" (1878), the easiest way
to answer these complicated tectological questions, and to support it
by the science of structure. It suffices to distinguish the three chief
stages I have mentioned, and to explain clearly their physiological
significance on the one hand and morphological on the other. We will
therefore consider the cell first, then the person (or sprout), and,
finally, the stock (or cormus).

Ever since the middle of the nineteenth century the cell theory has
been generally and rightly considered one of the most important
theories in biology. Every anatomical, histological, physiological, and
ontogenetic work must build on the idea of the cell as the elementary
organism. Nevertheless, we are still very far from having a general
and clear agreement as to this universal and fundamental idea. On
the contrary, the ablest biologists still differ considerably as to
the nature of the cell or the elementary individual, its relation to
the whole of the multicellular organism, and so on. This divergence
of views is partly due to the intricacy of the phenomena we find in
the life of the cell, and partly to the many and extensive changes
that have been made in the meaning of the term in the course of its
employment. Let us first cast a glance at the various stages of its
history.

When in the last third of the seventeenth century a number of
scientists, especially Malpighi in Italy and Crew in England, used the
microscope for the first time in the anatomic study of plant structure,
they noticed a certain build of the tissue that closely resembled the
honeycomb. The closely packed wax cells, filled with honey, of the
hive, which show a hexagonal appearance in section, are like the wood
cells that contain the sap in the plant. It was the great merit of
Schleiden, the real founder of the cell theory, to prove that _all_
the different tissues of plants are originally composed of such cells
(1838). Theodor Schwann soon afterwards proved the same for the animal
tissues; in 1839 he extended the theory to the whole organic world.
Both these scientists regarded the cell as essentially a vesicle, the
firm membrane of which enclosed a fluid content, and a solid smaller
body inside this, which R. Brown had recognized as the nucleus in 1833.
They compared the cell, as a microscopic individual, to an organic
crystal, and thought it arose by a sort of crystallization in an
organic medium (cytoblastema); in this the central nucleus would serve
as starting-point like the nucleus of the crystal.

In the first twenty years (1839-59) of the cell theory it was a fixed
principle that there were three essential parts of the cell. Firstly,
there was the strong outer membrane, which was not only regarded as a
protective covering, but also credited with a great deal of importance
as an element in the building of the organism. In the second place,
there was the fluid or semi-fluid content (the sap); and, thirdly,
the firm nucleus enclosed in the sap. In order to give a clearer idea
of the relative thickness and disposition of these parts, the cell
was compared to a cherry or a plum. The soft flesh of this fruit
(corresponding to the cell sap) can, with difficulty, be separated from
the external firm skin or from the hard stone within. A great step in
advance was made in 1860, when Max Schultze showed that the external
membrane was an unessential and secondarily formed part of the cell.
It is, as a fact, altogether wanting in many, especially young, cells
of the animal body. They are naked cells without any membrane. The
distinguished anatomist also proved that the so-called "cell sap"--the
real body of the cell--is not a simple fluid, but a viscous, albuminous
substance, the independent movements of which had long been known
in the rhizopods, and which the first to study it carefully, Felix
Dujardin, had described as _sarcode_ in 1835. Max Schultze further
showed that this "sarcode" was identical with the "cell mucus" of
the plant cells which Hugo Mohl had designated "protoplasm" in 1846,
and that this living matter must be regarded as the real vehicle
of the phenomena of life. As the membrane was now recognized to be
non-essential, of secondary growth, and completely wanting in some
cases, there remained only two essential parts of the cell--the outer
soft cell body, consisting of protoplasm, and the inner firm nucleus,
consisting of a similar substance called nuclein. The original naked
cell was now like a cherry or plum without the skin. This new idea of
the cell, formulated forty years ago, which I endeavored to confirm
in my monograph on the radiolaria (1862), is now generally accepted,
and the cell is defined as a granule or particle of protoplasm (=
cytoplasm) enclosing a firm and definite nucleus (or caryon, consisting
of caryoplasm).

This would be a good occasion to glance at the errors to which
microscopic investigation and the conclusions based on it are liable.
Although Kölliker in 1845, and Remak in 1851, had drawn attention to
the existence of naked cells, and had compared their movements (for
instance, in lymph-cells) to those of the protoplasm in plant-cells,
the majority of the leading microscopists clung for twenty years to
the dogma that every cell must have a membrane; the definite outline
which even a naked cell must show in a different refracting medium was
taken to be the sign of a special and anatomically separable membrane.
It would be just as correct to talk of a protective membrane on a
homogeneous glass ball; its outline is sharply defined. In the long
controversy that "exact" observers sustained as to the presence or
absence of a membrane, this optical error--the false interpretation
of a sharp contour--counted for a good deal. It is much the same
with other conflicts of "exact" observers who give their "certain
observations" as facts, whereas they are really inferences from
imperfect observations on which different interpretations may be put.

Forty years ago (1864) I tried in vain to detect a nucleus in the
naked, living, mobile protoplasm of a few small rhizopod-like protists
(protamœba and protogenes). Other observers, who afterwards studied
similar unnucleated cells (Gruber, Cienkowski, and others), were no
more successful. On the ground of these observations, which were often
repeated afterwards, I formed the class of the _monera_--the simplest
unnucleated organisms--in my _General Morphology_ in 1866, and pointed
out their great importance in solving some of the chief problems of
biology. This importance has been much enhanced of late, since the
chromacea and bacteria have also been recognized as unnucleated cells.
Bütschli has, it is true, raised the objection that their homogeneous
plasma-body behaves, not as cytoplasm, but as caryoplasm (or nuclein),
and so that these simplest plastids correspond, not to the cell-body,
but to the nucleus of other cells. On this view the bacteria and
chromacea are not cells without nuclei, but nuclei without cell-bodies.
This idea agrees with my own in conceiving the plasma-body of the
monera (apart from its molecular structure) as homogeneous and not yet
advanced as far as the characteristic differentiation of inner nucleus
and outer cell-body. Bearing in mind that these essential parts of
the cell (in the view of most cytologists) are chemically related yet
different from each other, we have three possible cases of the original
formation of the nucleated cell from the unnucleated cytode: (i) The
nucleus and cell-body have arisen by differentiation of a homogeneous
plasm (monera); (2) the cell-body is a secondary growth from the
primary nucleus; (3) the nucleus is a secondary development from the
cell-body.

On the first view, which I hold, the plasm, or living matter, of
the earliest organisms on the earth (which can only be conceived as
archigonous monera) was a homogeneous _plasson_ or archiplasm--that
is to say, a plasma-compound that was not yet differentiated into
outer cytoplasm and inner caryoplasm. The rise of this chemical
distinction--and the accompanying morphological division of cell-body
and nucleus--was due to a phyletic differentiation; it was the outcome
of a very early and most important division of labor. The hereditary
matter gathered in the nucleus, the outer cell-matter controlling the
intercourse with the external world. Thus, by this first ergonomy, the
nucleus became the vehicle of heredity and the cell-body the organ of
adaptation. Opposed to this view is the second, the hypothesis which
the founder of the cell-theory, Schleiden, had put forward--that the
nucleus is the original base of the cell, and the cell-body a secondary
development from it. This opinion (which, in the main, corresponds
to that of Bütschli) raises a number of difficulties; as does also
the third hypothesis, that the unnucleated "protoplasm-body" (the
outer cytoplasm-body) is the original formation, and that the nucleus
arose secondarily by condensation and chemical modification of it. At
the bottom, however, the difference between the three hypotheses on
the primary cytogenesis is not as great as it seems at first sight.
However, I am more inclined to adhere to the first; it supposes
that the physiological and chemical differences between nucleus and
cell-body, which afterwards became so important, were not originally
present. The phenomena of caryolysis in indirect cell-division show us
still how close are the relations of the two substances.

If the organic population of our planet has arisen naturally, and not
by a miracle, as Reinke and other vitalists suppose, the earliest
elementary organisms, produced by the chemical process of archigony
(spontaneous generation), could not be real nucleated cells, but
unnucleated cytodes of the type of the chromacea (_cf._ chapter ii.).
The nucleated real cell, as Oscar Hertwig and others define it to-day,
can only have arisen by phylogenetic differentiation of nucleus and
cell-body from the simple cytode of the monera. In that case it is a
matter of simple logic to distinguish the older cytode from the later
cell. The two may then best be comprised (as I proposed in vain in
1866) under the name of "plastids" (formative principles)--that is,
the elementary organism in the broader sense. But if it is preferred
to call the latter _cells_ (in the broader sense), the wrong modern
idea of the cell must be altered, and the nucleus-feature omitted from
it. The cell is then simply the living particle of plasm, and its two
stages of development must be described by other names. The unnucleated
plastid might be called _primitive cell_ (protocytos), and the ordinary
nucleated one the nuclear cell (caryocytos).

A long gradation of cellular organization leads from the simplest
primitive cells (monera) to the highest developed protists. While no
morphological organization whatever is discoverable in the homogeneous
plasma-body of the chromacea and bacteria, we find a composition from
different parts in the highly differentiated body of the advanced
protophyta (diatomes, siphonea) and protozoa (radiolaria, infusoria).
The manifold parts of the unicellular organism, developed by division
of work in the plasm, discharge various functions, and behave
physiologically like the organs of the multicellular histona. But
as the idea of "organ" in the latter is morphologically fixed as a
multicellular part of the body, made up of numerous tissues, we cannot
call these similarly functioning parts "organs of the cell," and had
better describe them as organella (or organoids).

The great majority of the protists are, in the developed condition,
as actual individuals, equivalent morphologically to real nucleated
cells. By means of adaptation to the most varied conditions and
the inheritance of the properties thus acquired such a variety of
unicellular forms has been evolved in the course of millions of
years that we can distinguish thousands of living species, both of
plasmodomous protophyta and plasmophagous protozoa. The number of
known and named species is already as high as this in several distinct
classes, as, for instance, in the diatomes of the primitive plants
and the radiolaria of the primitive animals. These solitary living
unicellulars, or "hermit-cells," may be called _monobia_.

Many other protists have abandoned this original solitary life; they
follow their social instincts and form communities or colonies of cells
(_cœnobia_). These are usually formed by the daughter-cells which
arise from the cleavage of a mother-cell remaining united after the
division, and so on with the succeeding generations which come from
their repeated segmentation. The following are the chief forms of these
cœnobia:

1. GELATINOUS CŒNOBIA.--The social cells secrete a structureless
mass of jelly, and remain associated in the common gelatinous mass,
without actual contact. Sometimes they are regularly, at other times
irregularly, distributed in it. We find cœnobia of this kind even
among the monera, such as the _zooglœa_ of many bacteria and
chromacea. They are common among the protophyta and protozoa.

2. SPHERICAL CŒNOBIA.--The cell-community forms a sort of ball,
the cells lying close together at its surface, touching each other or
even forming a continuous layer; such are _holosphæra_ and _volvox_
among the protophyta, _magosphæra_ and _synura_ among the protozoa.
The latter are particularly interesting because they resemble the
_blastula_, an important embryological stage of the metazoa, of which
the simple, epithelial cell-layer at the surface of the hollow sphere
is called the _blastoderm_ (or germinal membrane).

3. ARBOREAL CŒNOBIA.--The cell-community takes the form of a small
tree or shrub, the fixed cells secreting jelly-like stalks at their
base and these forming branches. At the top of each stalk or branch
is an independent cell; so in the case of the _gomphonema_ and many
other diatomes, the _codonocladium_ among the flagellata, and the
_carchesium_ among the ciliata.

4. CATENAL CŒNOBIA.--The cell-community forms a chain, the links of
which (the individual cells) are joined in a row. We find chainlike
cell-communities of this sort, or "articulated threads," even among the
monera (_oscillaria_ and _nostic_ among the chromacea, _leptothrix_
among the bacteria). Among the diatomes we have the _bacillaria_, among
the thalamophora _nodosaria_, as examples. Many of the lower protophyta
(algaria and algetta) form the direct transition to the true algæ among
the metaphyta, as the threadlike layer of the latter (for instance,
_cladophora_) is only a higher development of the catenal cœnobium,
with polymorphism of the co-ordinated cells. We may also regard these
articulated multicellular threads as the first sketch for the formation
of tissues in the metaphyta.

The stable communities of cells which make up the body of the histona,
or multicellular plants and animals, are called tissues (_tela_ or
_hista_). They differ from the cœnobia of the protists in that
the social cells give up their independence, assume different forms
in the division of labor, and subordinate themselves to the higher
unity of the organ. However, it would be just as difficult to lay
down a sharp limit between the cœnobia and the tissues as between
the protists and the histona which possess them; the latter have been
developed phylogenetically from the former. The original physiological
independence of the cells which have combined to form tissues is more
completely lost in proportion to the closeness of their combination,
the complexity of their division of labor, and the differentiation
and centralization of the tissue-organism. Hence the various kinds of
tissue in the body of the histona behave like the various classes and
professions in a state. The higher the civilization and the more varied
the classes of workers, the more they are dependent on each other, and
the state is centralized.

In the lower tissue-forming plants, the algæ and fungi, the plant-body
has the appearance of a layer of cells, the tissues of which show
little or no division of labor. In these _thallophyta_ there are
none of the conducting or vascular fibres, the formation of which
is of great importance in the higher plants in connection with
their physiological function of circulation of the sap. These more
advanced vascular plants comprehend the two great groups of ferns
(_pteridophyta_) and flowering plants (_anthophyta_, or phanerogams).
Their body is always composed of two chief organs, the axial stem
and the lateral leaves. This is also the case with the mosses
(_bryophyta_), which have no vascular fibres; they lie between the
two chief groups of the non-vascular thallophyta and the vascular
cormophyta. However, this histological and organological division of
the two great groups of tissue-plants must not be pressed; there are
many exceptions and intermediate forms. In general their manifold
tissue-forms may be brought under two chief groups, which we may call
primary and secondary. The primary tissues are the phylogenetically
older and histologically simple "cell-tissues," such as we have in the
thallophyta (algæ, fungi, and mosses); in these there are no conducting
fibres, or, at least, only rudimentary ones. The secondary tissues
are a later development from these; they form conducting and vascular
fibres and other highly differentiated forms of tissue (cambium, wood,
etc.). They make up the bodies of the more complex vascular plants, the
ferns and flowering plants.

In the bodies of the tissue-animals we may similarly distinguish two
chief groups of tissues, the primary and secondary. The former are
phylogenetically and ontogenetically older than the latter. The primary
tissues of the metazoa are the _epitelia_, simple layers of cells or
forms of tissue directly derived from such (glands, etc.). Secondary
tissues, evolved from the former by physiological change of work and
morphological differentiation, are the _apotelia_; of these "derivative
tissues" we may distinguish the three leading groups of connective
tissue, muscular tissue, and nerve tissue. These three great groups of
tissue in the animal world may be subdivided, like the plant groups,
into lower and higher sub-sections. The cœlenteria (gastræads,
sponges, cnidaria) are predominantly built up of epitelia, as are also
the phyletically older group of the cœlomaria; in the vast majority
of the latter, however, the great mass of the body is formed of
apotelia, and they are subject to the most extensive differentiation.
The embryo of all the metazoa consists solely of epitelia (the
germ-layers) at first; apotelia are developed from these afterwards by
differentiation of the tissues.

Comparative anatomy distinguishes in the multicellular body of the
tissue-forming organisms a great number of different parts, which are
regularly adapted to discharge definite vital functions, and have been
most intricately developed in virtue of the division of labor. They are
called "organs" in the stricter sense in opposition to the organella
(or organoids) of the protists; the latter have, it is true, a similar
physiological purport, but are not (being parts of a cell) equal to the
former morphologically. The remarkable efficiency that we find in the
structure of the various organs in view of the functions they have to
discharge, and the regularity of their construction in the unity of
the histon--in other words, their adaptive organization--is explained
mechanically by the theory of selection, while the teleological
hypotheses of dualistic biology (for instance, the "intelligent
dominants" of Reinke) completely fail to account for their origin. The
gradual advance of the organs and their physiological division of labor
have many analogies in the two kingdoms of the histona. While at the
lowest stages the simple organ represents only a separate individual
piece of primitive tissue, we find special systems of organs and
organic apparatus in the higher stages.

The idea of a particular system of organs is determined by the unity
of one tissue which forms the characteristic element in the totality
of the organs that belong to it. Of such systems in the kingdom of the
metaphyta we have: the skin-system (with the tissue of the epidermis),
the vascular system (with its conducting and vascular fibres), and the
complementary tissue system (with the basic tissue). In the kingdom of
the metazoa we may similarly distinguish: the skin-system (integument
of the epidermis), the vascular system (with the mesenchyma-tissue
of the blood and blood-vessels), the muscular system (with the
muscle-tissue), and the nervous system (with the neurona of the
nerve-tissue).

In contrast with the histological idea of a system of organs, we have
the physiological conception of an apparatus of organs. This is not
determined by the unity of the constituent tissue, but by the unity of
the lifework that is accomplished by the particular group of organs in
the histona. Such an apparatus of organs is, for instance, the flowers
and the fruit developing therefrom in the phanerogams, or the eye or
the gut of an animal. In these apparatus the most diverse organs and
systems of organs may be associated for the fulfilment of a definite
physiological task.

In the higher animals and plants we usually regard as the "real
individual" (in the wider sense of the word) the tissue-forming
organism made up of various organs; and we may here briefly and
instructively call this the histonal individual (or, more briefly,
the "histonal"). Botanists call this individual phenomenon among
the metaphyta a sprout (_blastus_). Zoologists give the title of
"person" (_prosopon_) to the corresponding unity among the animals.
The two forms agree very much in their general features, and may be
called "individuals of the second order," if we take the cells to be
the first and the stock the third stage in the hierarchy of organic
individuality. In comprising them here under the general head of
histonals, or histonal individuals, I mean by this to designate the
definite physiological unity of the multicellular and tissue-forming
organism, as contrasted with the unicellular protist on the one hand,
and the higher stem, made up of several histonals, on the other.

The plant-histonal, which Alexander Braun especially clearly marked
out and described as the sprout, is found in two principal forms in
the kingdom of the metaphyta--the lower form of the layer-sprout
(_thallus_) and the higher form of the stalk-sprout (_culmus_).
The thallus predominates in the lower and older sub-kingdom of the
layer-plants (_thallophyta_), in the classes of the algæ and fungi;
the culmus in the higher and younger sub-kingdom of the stalk-plants
(_cormophyta_), in the classes of the mosses, ferns, and flowering
plants. The culmus presents in general the characteristic form of
an axial central organ, the stalk, with lateral organs, the leaves,
attached to this at the sides, the former having an unlimited vertical
growth and the latter an unlimited basal growth. The thallus does not
yet show this important morphological division. There are, however,
exceptions in both groups of the metaphyta. The large and highly
developed _fucoidea_ among the algæ exhibit similar differentiations
of organs to those we distinguish as stalk and leaves in the higher
cormophyta. On the other hand, they are wanting in the lower
liverworts, which form a thallus like many of the algæ; thus, for
instance, the liverwort _riccia fluitans_ is just like the brown
alga _dictyota dichotoma_. Other primitive liverworts (such as the
_anthoceros_) have also a very simple thallus; but most of them have
a separation of the thallus into an axial organ (stalk) and several
lateral organs (leaves). In the distribution of labor among the
leaves there then emerge the differences between the lower leaves,
foliage leaves, higher leaves, and flower leaves. A simple poppy-plant
(_papaver_) or a single-flowered _gentiana ciliata_, which has only one
bloom at the top of its branchless stalk, is a good example of a highly
developed culmus.

To the plant-sprout corresponds in the animal world the _person_. All
the tissue-animals pass in the course of their embryonic development
through the important stage of the _gastrula_, or "cup-shaped embryo."
The whole body of the tissue-animal at this stage forms at first a
simple gut-sac or gastric sac (the primitive gut), the cavity of
which opens outward by a primitive mouth. The thin wall of the sac is
formed by two superimposed layers of cells, the two primary germinal
layers. This gastrula is the simplest form of the "person," and the two
germinal layers are its sole organs.

The diverse animal forms which develop along different lines
from this common embryonic form of the gastrula may be grouped
into two sub-kingdoms, the lower (_cœlenteria_) and the upper
(_cœlomaria_) animals. The former correspond in the simplicity of
their structure in many respects to the thallophyta, and the latter
to the cormophyta. Of the four stems of the cœlenteria (which
have only a ventral opening and no gut-cavity) the gastræads remain
at the gastrula stage, and the sponges are formed by multiplication
of the same stems of gastræads. On the other hand, the cnidaria
develop into higher radial (star-shaped) persons, and the platodes
into lower bilateral persons. From the latter are derived the worms
(_vermalia_), the common stem-groups of the five higher animal stems,
the unarticulated mollusks, echinoderms, and tunicates, and the
limb-forming articulates and vertebrates.

A large part of the physiological advantages and morphological
perfection which the higher histona have, as contrasted with the lower,
may be traced to the circumstance that the tissue-forming organism
articulates--that is to say, divides on its long axis into several
sections. With this multiplication of groups of organs there goes, as a
rule, a more or less extensive division of work among them, a leading
factor of higher development. In this point also we see the biogenetic
parallelism between the two great groups of the tissue-plants and
tissue-animals.

In the kingdom of the tissue-plants the articulated cormophyta rise
high above the unarticulated thallophyta. While the articulation of
the stem of the former proceeds and leaves are developed at the knots
(_nodi_) between each two sections of the stalk, far greater play is
offered to polymorphic differentiation than in the thallophyta, which
are generally without this metamerism. The formation of the bloom in
the flowering plants or phanerogams consists in a sexual division of
labor among the thickly gathered leaves in a short section of a stem.

To the two groups of unarticulated and articulated sprouts in the
kingdom of the tissue-plants correspond, in many respects, the two
sections of the tissue-animals, the unarticulated and the articulated.
The two stems of the articulates and vertebrates rise above all the
other metazoa by the perfection of their organism and the variety
of their functions. In the articulates the metamerism is chiefly
external--an articulation of the body wall. In the vertebrates it
mainly affects the internal organs, the skeleton, and the muscular
system. The vertebration (articulation) of the vertebrates is not
outwardly visible like that of the articulates. In both stems the
articulation is similar in the lower and upper forms, as we find in
the annelids and myriapods, the acrania and cyclostoma. On the other
hand, the higher the organization the greater is the unlikeness of
the members or articulated parts, as in the arachnida and insects,
the amphibia and amniotes. The same antithesis is found in the lower
and higher crustacea. This metamerism of the higher metazoa is of a
motor character, having been acquired through the manner of movement
of the lengthened body; but we find in some groups of the lower, and
usually unarticulated, metazoa a propagative metamerism, determined
by budding at the end; such is the strobilation of the chain-worms
and the scyphostoma polyps. The individual metamera (parts) that are
released from the end of the chain in these cases immediately show
their individuality. This is also the case with many of the annelids,
in which every member that is separated has the power to reproduce the
whole chain of metamera.

The third and highest stage of individuality to which the multicellular
organism attains is the stock or colony (_cormus_). It is usually
formed by a permanent association of histonals that are produced
by cleavage (imperfect segmentation or budding) from one histonal
individual. The great majority of the metaphyta form complex plants in
this sense. But among the metazoa we find this form of individuality
only in the lower (and generally stationary) stages of development.
Here also there is a striking parallelism of development between the
two chief groups of the histona. At the lower stages of stock-formation
there is equality of the social histonals. But in the higher grades
they become unequally developed in the division of labor; and the
greater the differences between them become, the greater is the
centralization of the whole stock (as in the case of the siphonophora).
We may therefore distinguish two principal forms of stocks--the
homonomous and heteronomous, the one without, and the other with,
division of labor among the histonals.

The history of civilization teaches us that its gradual evolution is
bound up with three different processes: (1) Association of individuals
in a community; (2) division of labor (ergonomy) among the social
elements, and a consequent differentiation of structure (polymorphism);
(3) centralization or integration of the unified whole, or rigid
organization of the community. The same fundamental laws of sociology
hold good for association throughout the entire organic world; and also
for the gradual evolution of the several organs out of the tissues
and cell-communities. The formation of human societies is directly
connected with the gregariousness of the nearest related mammals. The
herds of apes and ungulates, the packs of wolves, the flocks of birds,
often controlled by a single leader, exhibit various stages of social
formation; as also the swarms of the higher articulates (insects,
crustacea), especially communities of ants and termites, swarms
of bees, etc. These organized communities of free individuals are
distinguished from the stationary colonies of the lower animals chiefly
by the circumstance that the social elements are not bodily connected,
but held together by the ideal link of common interest.




VIII

FORMS OF LIFE

 Morphology--Laws of symmetry--Fundamental forms of animals
 and plants--Fundamental forms of protists and histona--Four
 chief classes of fundamental forms: (1) Centrostigma: vesicles
 (smooth vesicle and tabular vesicle); (2) Centraxonia: typical
 forms with central axis--Uniaxial (monaxonia, equipolar and
 unequipolar)--Transverse-axial (stauraxonia, double-pyramidal
 and pyramidal); (3) Centroplana: fundamental forms with
 central plane--Bilateral symmetry--Bilateral-radial and
 bilateral-symmetrical fundamental forms--Asymmetrical fundamental
 forms; (4) Anaxonia: irregular fundamental forms--- Causes of
 form-construction--Fundamental forms of monera, protists, and
 histona--Fundamental form and mode of life--Beauty of natural
 forms--Æsthetics of organic forms--Art forms in nature.


The infinite variety of forms which we observe in the realm of organic
life not only delight our senses with their beauty and diversity, but
also excite our curiosity, in suggesting the problem of their origin
and connection. While the æsthetic study of the forms of life provides
inexhaustible material for the plastic arts, the scientific study of
their relations, their structures, their origin and evolution, forms
a special branch of biology, the science of forms or morphology. I
expounded the principles of this science in my _General Morphology_
thirty-eight years ago. They are so remote from the ordinary curriculum
of education, and are so difficult to explain without the aid of
numerous illustrations, that I cannot think of going fully into
them here. In the present chapter I will only briefly describe those
features of living things which relate to the difficult question of
their ideal fundamental forms, the laws of their symmetry, and their
relation to crystal-formation. I have treated these intricate questions
somewhat fully in the last (eleventh) part of _Art-forms in Nature_.
The hundred plates contained in this work may serve as illustrations of
morphological relations. In the following pages the respective plates
are indicated by the letters A-f, with the number of each.

The unity of the organic structure, which expresses itself everywhere
in the fundamental features of living things and in the chemical
composition and constructive power of their plasm, is also seen in
the laws of symmetry in their typical forms. The infinite variety of
the species may, both in the animal and plant worlds, be reduced to
a few principal groups or classes of fundamental forms, and these
show no difference in the two kingdoms (_cf._ plate 6). The lily has
the same regular typical form as the hexaradial coral or anemone
(A-f, 9, 49), and the bilateral-radial form is the same in the
violet and the sea-urchin (clypeaster, A-f, 30). The dorsiventral or
bilateral-symmetrical form of most green leaves is repeated in the
frame of most of the higher animals (the cœlomaria); the distinction
of right and left determines in each the characteristic antithesis of
back and belly.

The distinction between protists and histons is much more important
than the familiar division of organisms into plants and animals, in
respect of their fundamental forms and their configuration. For the
protists, the unicellular organisms (without tissue) exhibit a much
greater freedom and variety in the development of their fundamental
forms than the histons, the multicellular tissue-forming organisms. In
the protists (both protophyta and protozoa) the constructive force of
the elementary organism, the individual cell, determines the symmetry
of the typical form and the special form of its supplementation; but in
the histons (both metaphyta and metazoa) it is the plasticity of the
tissue, made up of a number of socially combined cells, that determines
this. On the ground of this tectological distinction we may divide
the whole organic world into four kingdoms (or sub-kingdoms), as the
morphological system in the seventh table shows.

In respect of the general science of fundamental forms (promorphology),
the most interesting and varied group of living things is the class
of the radiolaria. All the various fundamental forms that can be
distinguished and defined mathematically are found realized in the
graceful flinty skeletons of these unicellular sea-dwelling protozoa.
I have distinguished more than four thousand forms of them, and
illustrated by one hundred and forty plates, in my monograph on the
_Challenger_ radiolaria [translated].

Only a very few organic forms seem to be quite irregular, without any
trace of symmetry, or constantly changing their formless shape, as we
find, for instance, in the amœbæ and the similar amœboid cells
of the plasmodia. The great majority of organic bodies show a certain
regularity both in their outer configuration and the construction of
their various parts, which we may call "symmetry" in the wider sense
of the word. The regularity of this symmetrical construction often
expresses itself at first sight in the arrangement side by side of
similar parts in a certain number and of a certain size, and in the
possibility of distinguishing certain ideal axes and planes cutting
each other at measurable angles. In this respect many organic forms
are like inorganic crystals. The important branch of mineralogy that
describes these crystalline forms, and gives them mathematical
formulæ, is called crystallography. There is a parallel branch of the
science of biological forms, promorphology, which has been greatly
neglected. These two branches of investigation have the common aim of
detecting an ideal law of symmetry in the bodies they deal with and
expressing this in a definite mathematical formula.

The number of ideal fundamental forms, to which we may reduce the
symmetries of the innumerable living organisms, is comparatively
small. Formerly it was thought sufficient to distinguish two or three
chief groups: (1) radial (or actinomorphic) types, (2) bilateral (or
zygomorphic) types, and (3) irregular (or amorphic) types. But when
we study the distinctive marks and differences of these types more
closely, and take due account of the relations of the ideal axes and
their poles, we are led to distinguish the nine groups or types which
are found in the sixth table. In this promorphological system the
determining factor is the disposition of the parts to the natural
middle of the body. On this basis we make a first distinction into four
classes or types: (1) the centrostigma have a _point_ as the natural
middle of the body; (2) the centraxonia a straight line (axis); (3) the
centroplana a plane (median plane); and (4) the centraporia (acentra or
anaxonia), the wholly irregular forms, have no distinguishable middle
or symmetry.


 I. CENTROSTIGMATIC TYPES.--The natural middle of the body is a
 mathematical point. Properly speaking, only one form is of this
 type, and that is the most regular of all, the sphere or ball.
 We may, however, distinguish two sub-classes, the smooth sphere
 and the flattened sphere. The smooth sphere (_holospœra_) is a
 mathematically pure sphere, in which all points at the surface are
 equally distant from the centre, and all axes drawn through the
 centre are of equal length. We find this realized in its purity
 in the ovum of many animals (for instance, that of man and the
 mammals) and the pollen cells of many plants; also cells that
 develop freely floating in a liquid, the simplest forms of the
 radiolaria (_actissa_), the spherical cœnobia of the volvocina
 and catallacta, and the corresponding pure embryonic form of the
 _blastula_. The smooth sphere is particularly important, because it
 is the only absolutely regular type, the sole form with a perfectly
 stable equilibrium, and at the same time the sole organic form which
 is susceptible of direct physical explanation. Inorganic fluids
 (drops of quicksilver, water, etc.) similarly assume the purely
 spherical form, as drops of oil do, for instance, when put in a
 watery fluid of the same specific weight (as a mixture of alcohol and
 water).

 The flattened sphere, or facetted sphere (_platnosphæra_), is known
 as an endospherical polyhedron; that is to say, a many-surfaced body,
 all the corners of which fall in the surface of a sphere. The axes
 or the diameters, which are drawn through the angles and the centre,
 are all unequal, and larger than all other axes (drawn through the
 facets). These facetted spheres are frequently found in the globular
 silicious skeletons of many of the radiolaria; the globular central
 capsule of many spheroidea is enclosed in a concentric gelatine
 envelope, on the round surface of which we find a net-work of fine
 silicious threads. The meshes of this net are sometimes regular
 (generally triangular or hexagonal), sometimes irregular; frequently
 starlike silicious needles rise from the knots of the net-work (A-f,
 1, 51, 91). The pollen bodies in the flower-dust of many flowering
 plants also often assume the form of facetted spheres.

 II. CENTRAXONIA TYPES.--The natural middle of the body is a straight
 line, the principal axis. This large group of fundamental forms
 consists of two classes, according as each axis is the sole fixed
 ideal axis of the body, or other fixed transverse axes may also
 be distinguished, cutting the first at right angles. We call the
 former uniaxial (_monaxonia_), and the latter transverse-axial
 (_stauraxonia_). The horizontal section (vertically to the chief
 axis) is round in the uniaxials and polygonal in the transverse-axial.

 In the monaxonia the form is determined by a single fixed axis,
 the principle axis; the two poles may be either equal (_isopola_)
 or unequal (_allopola_). To the isopola belong the familiar simple
 forms which are distinguished in geometry as spheroids, biconvex,
 ellipsoids, double cones, cylinders, etc. A horizontal section,
 passing through the middle of the vertical chief axis, divides the
 body into two corresponding halves. On the other hand, many of the
 parts are unequal in size and shape in the _allopola_. The upper pole
 or vertex differs from the basal pole or ground surface; as we find
 in the oval form, the planoconvex lens, the hemisphere, the cone,
 etc. Both sub-classes of the monaxonia, the allopola (conoidal) and
 the isopola (spheroidal), are found realized frequently in organic
 forms, both in the tissue-cells of the histona and the independently
 living protists (A-f, 4, 84).

 In the stauraxonia the vertical imaginary principal axis is cut by
 two or more horizontal cross-axes or radial-axes. This is the case in
 the forms which were formerly generally classed as regular or radial.
 Here also, as with the monaxonia, we may distinguish two sub-classes,
 isopola and allopola, according as the poles of the principal axis
 are equal or unequal.

 Of the _stauraxonia isopola_ we have, for instance, the double
 pyramids, one of the simplest forms of the octahedron. This form is
 exhibited very typically by most of the acantharia, the radiolaria
 in which twenty radial needles (consisting of silicated chalk) shoot
 out from the centre of the vertical chief axis. These twenty rays
 are (if we imagine the figure of the earth with its vertical axis)
 distributed in five horizontal zones, with four needles each, in
 this wise: two pairs cross at right angles in the equatorial zone,
 but on each side (in north and south hemispheres) the points of four
 needles fall in the tropical zone, and the points of four polar
 needles in the polar circles; twelve needles (the four equatorial
 and eight polar) lie in two meridian planes that are vertical to
 each other; and the eight tropical needles lie in two other meridian
 planes which cross the former at an angle of forty-five degrees.
 In most of the acantharia (the radial acanthometra and the mailed
 acanthophracta)--there are few exceptions--this remarkable structural
 law of twenty radial needles is faithfully maintained by heredity.
 Its origin is explained by adaptation to a regular attitude which
 the sea-dwelling unicellular body assumes in a certain stage of
 equilibrium (A-f, 21, 41). If the points of the real needles are
 connected by imaginary lines, we get a polyhedrical body, which may
 be reduced to the form of a regular double pyramid. This typical form
 of the equipolar stauraxonia is also found in other protists with a
 plastic skeleton, as in many diatomes and desmidiacea (A-f, 24). It
 is more rarely found embodied in the tissue-cells of the histona.

 Unequipolar stauraxonia are the pyramids, a fundamental form that
 plays an important part in the configuration of organic bodies. They
 were formerly described as regular or fundamental forms. Such are the
 regular blooms of flowering plants, the regular echinoderms, medusæ,
 corals, etc. We may distinguish several groups of them according to
 the number of the horizontal transverse axes that cut the vertical
 main axis in the middle.

 Two totally different divisions of the pyramidal types are the
 regular and the amphithecta pyramids. In the regular pyramids the
 transverse axes are equal, and the ground-surface (or base) is a
 regular polygon, as in the three-rayed blooms of the iris and crocus,
 the four-rayed medusæ (A-f, 16, 28, 47, 48, etc.), the five-rayed
 "regular echinoderms," most of the star-fish, sea-urchins, etc. (A-f,
 10, 40, 60), and the six-rayed "regular corals" (A-f, 9, 69).

 The amphithecta (or two-edged) pyramids, a special group of
 pyramidal types, are characterized by having as their basis a
 rhombus instead of a regular polygon. We may, therefore, draw two
 imaginary transverse axes, vertical to each other, through the
 ground-surface, both equipolar, but of unequal length. One of the
 two may be called the sagittal axis (with dorsal and ventral pole),
 and the other the transverse axis (with right and left pole); but
 the distinction is arbitrary, as the two are equipolar. In this lies
 the chief difference from the centroplane and dorsiventral forms, in
 which only the lateral axis is equipolar, the sagittal axis being
 unequipolar. We find the bisected pyramid in a very perfect form in
 the class of the ctenophora (or comb-medusæ, A-f, 27), where it is
 quite general. The striking typical form of these pelagic cnidaria
 is sometimes called biradial, sometimes four-rayed and bilateral,
 and sometimes eight-rayed-symmetrical. Closer study shows it to be a
 rhombus-pyramid. The originally four-rayed type, which it inherited
 from craspedote medusæ, has become bilateral by the development of
 different organs to the right and left from those before and behind.

 Similar rhombo-pyramidal forms to those of the ctenophora are also
 found in some of the medusæ and siphonophora, many of the corals and
 other cnidaria, and many flowers. The name "two-edged" which is given
 to this special type is taken from the ancient two-edged sword. Its
 chief axis is unequipolar, the handle being at the basic pole and
 the point at the verticle pole; but the two edges left and right are
 equal (poles of the lateral axis), and also the two broad surfaces
 (dorsal and ventral, joined by the sagittal axis).

 III. CENTROPLANE TYPES.--The natural middle of the body is a plane,
 the median or chief plane (_planum medianum_ or _sagittale_); it
 divides the bilateral body into two symmetrical halves, the right
 and the left. With this is associated the characteristic antithesis
 of back (_dorsum_) and belly (_venter_); hence, in botany this
 type (found, for instance, in most green leaves) is called the
 dorsiventral, and in zoology the bilateral in the narrower sense. One
 characteristic of this important and wide-spread type is the relation
 of three different axes, vertical to each other; of these three
 straight axes (enthyni) two are unequipolar and the third equipolar.
 Hence, the centroplanes may also be called tri-axial (_triaxonia_).
 In most of the higher animals (as in our own frame) the longest of
 the three axes is the principal one (_axon principalis_); its fore
 pole is the oral or mouth pole, and its hinder pole is the aboral
 or caudal (tail) pole. The shortest of the three enthyni is, in our
 body, the sagittal (arrow) or dorsiventral axis; its upper pole is
 at the back and its lower pole at the belly. The third axis--the
 transverse or lateral axis--is equipolar, one pole being called the
 right and the other the left. The various parts which make up the two
 halves of the body have relatively the same disposition in each half;
 but absolutely speaking (namely, in relation to the middle plane)
 they are oppositely arranged.

 Further, the centroplane or bilateral forms are also characterized
 by three vertical axes which may be drawn through each of the normal
 axes. The first of these normal planes is the median plane; it is
 defined by the chief axis and the sagittal axis, and divides the body
 into two symmetrical halves, the right and left. The second normal
 plane is the frontal plane; this passes through the chief axis and
 the transverse axis (which is parallel to the frontal surface in
 our body), and divides the dorsal half from the ventral half. The
 third normal plane is the cingular (waist) plane: this is defined by
 the sagittal and transverse axes. It divides the head half (or the
 vertical part) from the tail half (or the basal part).

 The name "bilateral symmetry," which is especially applied to the
 centroplane and dorsiventral types, is ambiguous, as I pointed out
 in 1866 in an exhaustive analysis and criticism of these fundamental
 forms in the fourth book of the _General Morphology_. It is used in
 five different senses. For our present general purpose it suffices to
 distinguish two orders of centroplane types, the bilateral-radial and
 the bilateral-symmetrical; in the former the radial (pyramidal) form
 is combined with the bilateral, but not in the latter.

 The bilateral-radial type comprises those forms in which the radial
 structure is combined in a very characteristic fashion with the
 bilateral. We have striking examples in the three-rayed flowers
 of the orchids (A-f, 74), the five-rayed blooms of the labiate
 and papilionaceous flowers, etc., in the plant world; and in the
 five-rayed "irregular" echinoderms, the bilateral sea-urchins
 (spatangida, clypeastrida, A-f, 30) in the animal world. In these
 cases the bilateral symmetry is recognizable at the first glance, as
 is also the radial structure, or the composition from three to five
 or more raylike parts (paramera), which are arranged bilaterally
 round a common central plane.

 The bilateral-symmetrical type is general among the higher animals
 which move about freely. The body consists of two antithetic parts
 (_antimera_), and has no trace of radial structure. In the free
 moving, creeping, or swimming animals (vertebrates, articulates,
 mollusks, annelids, etc.) the ventral side is underneath, against the
 ground, and the dorsal side upward. This form is clearly the most
 useful and practical of all conceivable types for the movement of
 the body in a definite direction and position. The burden is equally
 distributed between the two sides (right and left); the head (with
 the sense organs, the brain, and the mouth) faces frontward and the
 tail behind. For thousands of years all artificial vehicles (carts on
 land and ships in water) have been built on this type. Selection has
 recognized it to be the best and preserved it, while it has discarded
 the rest. There are, however, other causes that have produced the
 predominance of this type in green leaves--the relation to the
 supporting stalk, to the sunlight that falls from above, etc.

Special notice must be taken of those bilateral forms which were
originally symmetrical (by heredity), but have subsequently become
asymmetrical (or of unequal halves), by adaptation to special
conditions of life. The most familiar example among the vertebrates
are the flat-fishes (_pleuronectides_), soles, flounders, turbots,
etc. These high and narrow and flattened boney-fishes have a perfect
bilateral symmetry when young, like ordinary fishes. Afterwards they
form the habit of laying on one side (right or left) at the bottom of
the sea; and in consequence the upper side, exposed to the light, is
dark colored, and often marked with a design (sometimes very like the
stony floor of the ocean--a protective coloring), while the side the
flat-fish lies on remains without color. But, what is more curious,
the eye from the under side travels to the upper side, and the two
eyes lie together on one side (the right or left); while the bones of
the skull and the softer parts of each side of the head grow quite
crooked. Naturally, this ontogenetic process, in which a striking lack
of symmetry succeeds to the early complete symmetry of each individual,
can only be explained by our biogenetic law; it is a rapid and brief
recapitulation (determined by heredity) of the long and slow phyletic
process which the flat-fish has undergone for thousands of years in its
ancestral history to bring about its gradual modification. At the same
time, this interesting metamorphosis of the _pleuronectides_ gives us
an excellent instance of the inheritance of acquired characteristics,
as a consequence of constant œcological habit. It is quite
impossible to explain it on Weismann's theory of the germ-plasm.

We have another striking example among the invertebrates in the snails
(_gasteropoda_). The great majority of these mollusks are characterized
by the spiral shape of their shells. This variously shaped, and often
prettily colored and marked, snail's house is in essence a spirally
coiled tube, closed at the upper end and open at the lower (or mouth):
the mollusk can at any moment withdraw into its tube. The comparative
anatomy and ontogeny of the snails teach us that this spiral shell
came originally from a simple discoid or cylindrical dorsal covering
of the once bilateral-symmetrical mollusk, by the two sides of the
body having an unequal growth. The cause of it was a purely mechanical
factor--the sinking of the growing visceral sac, covered with the
shell, to one side; one part of the viscera contained in it (the
heart, kidneys, liver, etc.) grew more strongly on one side than the
other in consequence of this; and this was accompanied by considerable
displacement and modification of the neighboring parts, especially the
gills. In most snails one of the gills and kidneys and the ventricle
of the heart corresponding to these have disappeared altogether,
only those of the opposite side remaining; and the latter have moved
from the right side to the left, or vice versa. The conspicuous lack
of symmetry between the two halves of the body which resulted from
this finds expression in the spiral form of the snail's shell. This
remarkable ontogenetic metamorphosis also can be fully explained by a
corresponding phylogenetic process, and affords a very fine instance of
the inheritance of acquired characters.

There are also many examples of this asymmetry of bilateral forms in
the plant world, such as the green foliage-leaves of the familiar
begonia and the blooms of _canna_.

IV. THE CENTRAPORIA.--Few organic forms are completely irregular and
without axes, as usually the attraction to the earth (geotaxis) or to
the nearest object determines the special direction of growth, and so
the formation of an axis in some direction or other. Nevertheless,
we may instance as quite irregular the soft and ever-changing
plasma-bodies of many rhizopods, the amœbinæ, mycetozoa, etc. Most
of the sponges also--which we regard as stocks of gastræads--are
completely irregular in structure; the most familiar example is the
common bath-sponge.

An impartial and thorough study of organic forms has convinced me that
their actual, infinitely varied configurations may all be reduced
to the few typical forms I have described. Comparative anatomy and
ontogeny further teach us that the countless modifying processes
which have led to the appearance of the various species have acted by
adaptation to different environments, habits, and customs, and give
us, in conjunction with heredity, a physiological explanation of this
morphological transformation. But the question arises as to the origin
of these few geometrically definable types, and the cause of their
divergence.

In this important and difficult question we find a great variety
of opinions and a strong leaning to dualistic and mystic theories.
Educated laymen, who have only a partial and imperfect acquaintance
with the biological facts, think that they are justified here in
appealing to a supernatural creation of forms. They contend that only a
wise creator, following a rational and conscious design, could produce
such structures. Even distinguished and informed scientists lean in
this matter towards mystic and transcendental ideas; they believe that
the ordinary natural forces do not suffice to explain these phenomena,
and that at least for the first construction of these fundamental types
we must postulate a deliberate creative thought, a design, or some such
teleological cause, and therefore consciously acting final causes. So
say Nägeli and Alexander Braun.

In direct opposition to this, I have ever maintained the view that the
action of familiar physical forces--mechanical efficient causes--fully
suffices to explain the origin and transformation of these fundamental
types, as well as for all other biological and inorganic processes. In
order to understand this monistic position thoroughly, and to meet the
errors of dualism, we must bear in mind always the radical processes of
growth which control all organic and inorganic configuration, and also
the long chain of advancing stages of development, which lead us from
the simplest protists, the monera, to the most advanced organisms.

The unicellular organisms exhibit the greatest variety from the
promorphological point of view. In the single class of the radiolaria
we find all imaginable geometrical types represented. This is seen
in a glance at the one hundred and forty plates on which I have
depicted thousands of these graceful little protozoa in my monograph
(_Challenger Report_, vol. xviii.). On the other hand, the monera, at
the lowest stage of organic life, the structureless organisms without
organs that live on the very frontier of the inorganic world, are very
simple. Especially interesting in this connection are the chromacea,
which have hitherto been so undeservedly and so incomprehensibly
neglected. Among the well-known and widely distributed chroococcacea,
the chroococcus, cœlosphærium, and aphanocapsa are quite the most
primitive of all organisms known to us--and at the same time the
organisms that enable us best to understand the origin of life by
spontaneous generation (archigony). The whole organism is merely a
tiny, bluish-green globule of plasm, without any structure, or only
surrounded by a thin membrane; its fundamental form is the simplest of
all, the centraxial smooth sphere. Next to these are the oscillaria
and nostochina, social chromacea, which have the appearance of thin,
bluish-green threads. They consist of simple primitive (unnucleated)
cells joined to each other; they seem often to be flattened into a
discoid shape as a result of close conjunction. Many protists are found
in two conditions, one mobile with very varied and changeable forms,
and one stationary with a globular shape. But when the separate living
cell begins to form a firm skeleton or protective cover for itself,
it may assume the most varied and often most complicated forms. In
this respect the class of the radiolaria among the protozoa, and the
class of the diatomes among the protophyta (both of which have flinty
shells), surpass all the other groups of the diversified realm of the
protists. In my _Art-forms in Nature_ I have given a selection of their
most beautiful forms (diatomes, A-f, 4, 84; radiolaria, A-f, 1, 11, 21,
22, 31, 41, 51, 61, 71, 95). The most remarkable and most important
fact about them is that the artistic builders of these wonderful and
often very ingenious and intricate flinty structures are merely the
plastidules or micella, the molecular and microscopically invisible
constituents of the soft viscous plasm (sarcode).

The configuration of the histona differs essentially from that of
the protists, since in the case of the latter the simple unicellular
body produces for itself alone the whole form and vital action of the
organism, while in the histona this is done by the cell state, or the
social combination of a number of different cells, which make up the
tissue body. Hence the ideal type which we can always define in the
actual histonal form has quite a different significance from that in
the unicellular protists. In the latter we find the utmost diversity in
the configuration of the independent living cells and the protective
cover it forms; among the histona the number of fundamental forms
is limited. It is true that the cells themselves which make up the
tissues may exhibit a great variety in form and structure; but the
number of the different tissues which they make up is small, and so
is the number of ideal types exhibited by the organism they combine
to form--the sprout (_culmus_) in the plant kingdom and the person in
the animal kingdom. The same may be said of the stock (_cormus_) in
both kingdoms--that is to say, of the higher individual unity which is
constituted by the union of several sprouts or persons.

The two classes of fundamental forms which are especially found in the
plant sprouts or the animal persons are the radial and bilateral. The
one is determined by the stationary life, the other by free movement in
a certain attitude and direction (swimming in water or creeping on the
ground). Hence we find the radial form (as pyramidal) predominant in
the blooms and fruits of the metaphyta, and the persons of the polyps,
corals, and regular echinoderms. On the other hand, the bilateral or
dorsiventral form preponderates in most free-moving animals; though
it is also found in many flowers (papilionaceous and labial flowers,
orchids, and others that are fertilized by insects). Here we have
to seek the cause of the bilateralism in different features, in the
relations with the insects, in the mode of their fastening to and
distribution on the stalk (for the green foliage leaves), and so on.

The complex individuals of the first order, the stocks (_cormi_), are
more dependent in their growth on the spatial conditions of their
environment than the sprouts or persons; hence their typical form is
generally more or less irregular, and rarely bilateral.

The interest which we take in natural and artistic forms, and which
has for thousands of years prompted men to reproduce the former in
the latter, depends for the most part, if not altogether, on their
beauty--that is to say, on the feeling of pleasure we experience in
looking at them. The causes of this pleasure and joy in the beautiful
and the naturalness of its development are explained in æsthetics. When
we combine this science with the results of modern cerebral physiology,
we may distinguish two classes of beauty--direct and indirect. In
direct or sensible beauty the internal sense-organs, or the æsthetic
neurona or sense-cells of the brain, are immediately affected with
pleasure. But in indirect or associational beauty these impressions
are combined with an excitement of the phronetic neurona--the rational
brain-cells which effect presentation and thought.

Direct or sensible beauty (the subject of sensual æsthetics) is the
direct perception of agreeable stimuli by the sense-organs. We may
distinguish the following stages of its perfection: 1. Simple beauty
(the subject of primordial æsthetics); the pleasure is evoked by the
direct sense-impression of a simple form or color. Thus, for instance,
a wooden sphere makes an agreeable impression as compared with a
shapeless piece of wood, a crystal as compared with a stone, a sky-blue
or golden-yellow spot as compared with a greenish-blue or dull-yellow
one (in music a simple pure bell-tone as compared with a shrill
whistle). 2. Rhythmic beauty (the subject of linear æsthetics); the
æsthetic sensation is caused by the serial repetition of some simple
form--for instance, a pearl necklace, a chainlike community of monera
(nostoc) or of cells (diatomes, A-f, 84, figs. 7 and 9): in music a
tasteful series of simple notes. 3. Actinal beauty (the subject of
radial æsthetics); the pleasure is excited by the orderly arrangement
of three or more homogeneous simple forms about a common centre, from
which they radiate; for instance, a regular cross or a radiating
star, the three counter-pieces in the iris-bloom, the four paramera
in the body of the medusa, the five radial-pieces in the star-fish.
The familiar experience of the kaleidoscope shows how amply the simple
radial constellation of three or more simple figures may delight
our æsthetic sense (in music we have the simple harmony of several
simultaneous notes). 4. Symmetrical beauty (the subject of bilateral
æsthetics); the pleasure is caused by the relation of a simple object
to its like, the mutual completion of two similar halves (the right and
left parts). When we fold a piece of paper over an ink-stain in such a
way that it is equally impressed on both halves of the fold, we get a
symmetrical figure which makes an agreeable impression on our natural
sense of space or equilibrium.

The æsthetic impressions in indirect associational beauty (the subject
of associative or symbolical æsthetics) are not only much more varied
and complex than those we have described, but they also play a much
more important part in the life of man and the higher animals. The
anatomic condition for this higher physiological function is the
elaborate construction of the brain in the higher animals and man,
and particularly the development of the special association-centres
(thought-centres, reason-sphere) and their differentiation from the
internal sense-centres. In this millions of different neurona or
psychic cells co-operate, the sensual æstheta acting in conjunction
with the rational phroneta, and thus, by complex associations of
ideas, much higher and more valuable functions arise. We may indicate
four chief groups of this associational or indirect beauty. 5.
Biological beauty (the subject of botanical and zoological æsthetics):
the various forms of organisms and their organs (for instance, a
flower, a butterfly) excite our æsthetic interest by association with
their physiological significance, their movements, their bionomic
relations, their practical use, and so on. 6. Anthropistic beauty
(the subject of anthropomorphic æsthetics): man, as "the measure of
all things," regards his own organism as the chief object of beauty,
either morphologically considered (beauty of the whole body and
its various organs--the eyes, mouth, hair, flesh-tint, etc.), or
physiologically (beauty of movements or positions), or psychologically
(the expression of the emotions in the physiognomy). As man transfers
to the objective world this personal gratification he experiences from
self-consideration, and anthropomorphically regards other beings in
the light of them, this anthropistic æsthetic obtains a far-reaching
significance. 7. Sexual beauty (the subject of erotic æsthetics): the
pleasure is caused by the mutual attraction of the sexes. The supreme
importance of love in the life of man and most other organisms,
the powerful influence of the passions, the sexual selection that
is associated with reproduction, have evoked an infinite number of
æsthetic creations in every branch of art relating to the antithesis of
man and woman. The special pleasure which is caused by the bodily and
mental affinities of the sexes can be traced phylogenetically to the
cell-love of the two sexual cells, or the attraction of the sperm-cell
to ovum. 8. Landscape beauty (the subject of regional æsthetics): the
pleasure which is caused by the sight of a fine landscape, and that
finds satisfaction in modern landscape-painting, is more comprehensive
than that of any other æsthetic sensations. In point of space the
object is larger and richer than any of the individual objects in
nature which are beautiful and interesting in themselves. The varying
forms of the clouds and the water, the outline of the blue mountains
in the background, the woods and meadows in the middle-distance,
and the living figures in the foreground, excite in the mind of the
spectator a number of different impressions which are woven together
into a harmonious whole by a most elaborate association of ideas. The
physiological functions of the nerve-cells in the cortex which effect
these æsthetic pleasures, and the interaction of the sensual æstheta
with the rational phroneta, are among the most perfect achievements
of organic life. This "regional æsthetics," which has to establish
scientifically the laws of landscape beauty, is much younger than the
other branches of the science of the beautiful. It is very remarkable
that absolute irregularity, the absence of symmetry and mathematical
forms, is the first condition for the beauty of a landscape (as
contrasted with architecture, and the beauty of separate objects in
nature). Symmetrical arrangement of things (such as a double row of
poplars or houses) or radial figures (a flower-bed or artificial wood)
do not please the finer taste for landscape; they seem tedious.

A comparative survey of these eight kinds of beauty in natural forms
discovers a connected development, rising from the simple to the
complex, from the lower to the higher. This scale corresponds to the
evolution of the sense of beauty in man, ontogenetically from the
child to the adult, phylogenetically from the savage to the civilized
man and the art critic. The stem-history of man and his organs, which
explains to us in anthropogeny the gradual rise from lower to higher
forms by the interaction of heredity and adaptation, also finds an
application in the history of æsthetics and ornamentation. It teaches
us how feeling, taste, emotion, and art have been gradually evolved. On
the other hand, we have corresponding to this evolutionary series the
scale of the typical forms which lie at the root of the real forms of
bodies both in nature and art.




SEVENTH TABLE

THE MORPHOLOGICAL SYSTEM OF ORGANISMS

Division of living things (plants and animals) into two kingdoms
(protista and histona) on the ground of their cell-structure and
body-structure.


  ┌──────────────────────────────────────────────────────────┐
  │  First organic kingdom: UNICELLULAR, protista.           │
  │                                                          │
  │Organisms which as a rule remain unicellular              │
  │throughoutlife (_monobia_), less frequently they          │
  │form loose cell communities (_cœnobia_) by                │
  │repeated cleavage, but never real tissues.                │
  │                                                          │
  │            Sub─kingdom of the protista.                  │
  ├───────────────────────────┬──────────────────────────────┤
  │    A. PRIMITIVE PLANTS    │     B. PRIMITIVE ANIMALS     │
  │       (protophyta).       │          (protozoa).         │
  │                           │                              │
  │      A. Character:        │        B. Character:         │
  │      Plasmodomous.        │        Plasmophagous.        │
  │                           │                              │
  │     Unicellulars with     │      Unicellulars with       │
  │    vegetal metabolism:    │      animal metabolism:      │
  │   Carbon─assimilation.    │    Albumin─assimilation.     │
  │                           │                              │
  │      CHIEF GROUPS:        │        CHIEF GROUPS:         │
  │                           │                              │
  │     I. Phytomonera        │        I. Zoomonera.         │
  │                           │                              │
  │Protophyta without nucleus │  Protozoa  without  nucleus  │
  │         (monera)          │          (monera).           │
  │        Chromacea          │          Bacteria.           │
  │                           │                              │
  │     II. Algariæ.          │        II. Sporozoa.         │
  │                           │                              │
  │Unicellular algæ with      │ Nucleated protozoa without   │
  │nucleus, without ciliary   │ mobile processes: Gregarinæ, │
  │motion: Paulotomea,        │ chytridinæ.                  │
  │diatomea.                  │                              │
  │                           │                              │
  │     III. Algettæ.         │        III. Rhizopoda.       │
  │                           │                              │
  │Unicellular algæ with      │ Nucleated  protozoa  with    │
  │nucleus, and with ciliary  │ pseudopodia: Labosa,         │
  │motion: Mastigota,         │ radiolaria.                  │
  │melthallia, siphonea.      │                              │
  │                           │        IV. Infusoria.        │
  │                           │                              │
  │                           │ Nucleated protozoa with      │
  │                           │ cilia or lashes:             │
  │                           │ Flagellata, ciliata.         │
  └───────────────────────────┴──────────────────────────────┘


  ┌────────────────────────────────────────────────────────────┐
  │      Second organic kingdom: MULTICELLULAR, histona.       │
  │                                                            │
  │ Organisms which are only unicellular at the                │
  │ beginning of their existence, are later                    │
  │ multicellular, and always form real tissues                │
  │ (_histobia_) by the firm conjunction of social cells.      │
  │                                                            │
  │              Sub─kingdom of the histona.                   │
  ├────────────────────────────┬───────────────────────────────┤
  │      C. TISSUE PLANTS      │    D. TISSUE ANIMALS          │
  │        (metaphyta).        │        (metazoa).             │
  │                            │                               │
  │        C. Character:       │       D. Character:           │
  │        Plasmodomous.       │       Phasmophagous.          │
  │                            │                               │
  │    Multicellulars with     │    Multicellulars with        │
  │    vegetal metabolism:     │     animal metabolism:        │
  │   Carbon─assimilation.     │    Albumin─assimilation.      │
  │                            │                               │
  │       CHIEF GROUPS:        │       CHIEF GROUPS:           │
  │                            │                               │
  │      I. Thallophyta.       │       I. Cœlenteria           │
  │                            │       (cœlenterata).          │
  │ Thallus─plants. Metaphyta  │                               │
  │ with thallus: Algæ, mycetæ │ Metazoa without body          │
  │ (fungi).                   │ cavity and anus: Gastræada.   │
  │                            │ Sponges, cnidaria, platodes.  │
  │       II. Mesophyta.       │                               │
  │                            │        II. Cœlomaria          │
  │ Median plants, with        │        (bilaterals).          │
  │ prothallium: Mosses, ferns │                               │
  │ (muscinæ filicinæ).        │ Metazoa with body cavity      │
  │                            │ and anus (generally also      │
  │                            │ blood─vessels). Vermalia,     │
  │      III. Anthophyta       │ mollusca, echinoderma,        │
  │       (phanerogams).       │ articulata, tunicata,         │
  │                            │ vertebrata.                   │
  │ Flowering  plants, with    │                               │
  │ blooms and seeds           │                               │
  │ (spermophyta):             │                               │
  │ Gymnosperms, angiosperms.  │                               │
  │                            │                               │
  │                            │                               │
  │                            │                               │
  │                            │                               │
  └────────────────────────────┴───────────────────────────────┘




IX

MONERA

 The simplest forms of life--Cell theory and cell dogma--Precellular
 organisms: monera, cytodes, and cells--Actual monera--Chromacea
 (cyanophyceæ)--Chromatophora--Cœnobia of chromacea: vital
 phenomena--Bacteria--Relations of the bacteria to the chromacea,
 the fungi, and the protozoa--Rhizomonera (protamœba, protogenes,
 protomyxa, bathybius)--Problematic monera--Phytomonera (plasmodoma)
 and zoomonera (plasmophaga)--Transition between the two classes.


In the study and explanation of all complex phenomena the first
thing to do is to understand the simple parts, the manner of their
combination, and the development of the compound from the simple. This
principle applies generally to inorganic objects, such as minerals,
artificially constructed machines, etc. It is also of general
application in biological work. The efforts of comparative anatomy are
directed to the comprehension of the intricate structure of the higher
organisms from the rising scale of organization and life in the lower,
and the origin of the former by historical development from the latter.
The modern science of the cell (cytology), which has in a short time
attained a considerable rank, pursues a method in opposition to this
principle. The intricate composition of the unicellular organism, in
many of the higher protists (such as the ciliata and infusoria) and
many of the higher tissue-cells (such as the neurona) has led to the
erroneous ascription of a highly complex organization to the cell in
general. One would be justified in saying that of late the cell-theory
has established itself in the dangerous and misleading position of a
cell-dogma.

The modern treatment of the science, as we find it in numbers of recent
works, even in some of the most distinguished manuals, and which we
must resent on account of its dogmatism, culminates in something like
the following theses:

1. The nucleated cell is the general elementary organism; all living
things are either unicellular, or made up of a number of cells and
tissues.

2. This elementary organism consists of at least two different organs
(or, more correctly, organella), the internal nucleus and the outer
cell-body (or cytoplasm).

3. The matter in each of these cell-organs--the caryoplasm of the
nucleus and the cytoplasm of the body--is never homogeneous (or
consisting of a chemical substratum), but always "organized," or
made up of several chemically and anatomically different elementary
constituents.

4. The plasm (or protoplasm) is, therefore, a morphological, not a
chemical, unity.

5. Every cell comes (and has come) only from a mother-cell, and every
nucleus from a mother-nucleus (_omnis cellula e cellula--omnis nucleus
e nucleo_).

These five theses of the modern cell-dogma are by no means sound; they
are incompatible with the theory of evolution. I have, therefore,
consistently resisted them for thirty-eight years, and consider them
to be so dangerous that I will briefly give my reasons. First, let
us clearly understand the modern definition of the cell. It is now
generally defined (in accordance with the second thesis) as being
composed of two essentially different parts, the nucleus and the
cell-body, and it is added that these organella differ constantly
both in respect of chemistry, morphology, and physiology. If that
is really so, the cell cannot possibly be the primitive organism; if
it were, we should have a miracle at the beginning of organic life
on the earth. The theory of natural evolution clearly and distinctly
demands that the cell (in this sense) is a secondary development from
a simpler, primary, elementary organism, a homogeneous cytode. There
are still living to-day very simple protists which do not tally with
this definition, and which I designated _monera_ in 1866. As they must
necessarily have preceded the real cells, they may also be called
"precellular organisms."

The earliest organisms to live on the earth, with which the wonderful
drama of life began, can, in the present condition of biological
science, only be conceived as homogeneous particles of plasm--biogens
or groups of biogens, in which there was not yet the division of
nucleus and cell-body which characterizes the real cell. I gave the
name "cytodes" to these unnucleated cells in 1866, and joined them
with the real nucleated cells under the general head of "plastids."
I also endeavored to prove that such cytodes still exist in the form
of independent monera, and in 1870 I described in my _Monograph on
the Monera_ a number of protists which do not tally with the above
definition.

Fifty years ago I made the first careful observations of living monera
(_protamœba_ and _protogenes_), and described them in my _General
Morphology_ (vol. i., pp. 133-5; vol. ii., p. xxii.) as structureless
organisms without organs and the real beginnings of organic life.
Soon afterwards, during a stay in the Canary Islands, I succeeded
in following the continuous life-history of a related organism of
the rhizopod type, which behaved like a very simple mycetozoon, but
differed in having no nucleus; I have reproduced the picture of it in
the first plate of my _History of Creation_. The description of this
orange-red globule of plasm (_protomyxa aurantiaca_) appeared first in
my _Monograph on the Monera_. Most of the organisms which I comprised
under this name exhibited the same movements as true rhizopods (or
sarcodina). It was afterwards proved of some of them that there was
a nucleus hidden within the homogeneous particle of plasm, and that,
therefore, they must be regarded as real cells. But this discovery
was wrongly extended to the whole of the monera, and the existence of
unnucleated organisms was denied altogether. Nevertheless, there are
living to-day several kinds of these organisms without organs, some
of them being very widely distributed. The chief examples are the
chromacea and the bacteria, the former with vegetal and the latter with
animal metabolism (or the former plasmodomous = plasma-forming, and the
latter plasmophagous = plasma-feeding). On the ground of this important
chemical difference, I distinguished two principal groups of the monera
in my _Systematic Phylogeny_ twenty years ago--the phytomonera and
the zoomonera, the former being unnucleated protophyta and the latter
unnucleated protozoa.

Among living organisms the chromacea are certainly the most primitive
and the nearest to the oldest inhabitants of the earth. Their simplest
forms, the chroococcacea, are nothing but small structureless particles
of plasm, growing by plasmodomism (formation of plasm) and multiplying
by simple cleavage as soon as their growth passes a certain limit
of individual size. Many of them are surrounded by a thin membrane
or somewhat thicker gelatinous covering, and this circumstance had
prevented me for some time from counting the chromacea as monera.
However, I became convinced afterwards that the formation of a
protective cover of this kind around the homogeneous particle of
plasm may indeed be regarded from the physiological stand-point as a
"purposive" structure, but at the same time may be looked upon, from
the purely physical stand-point, as a result of superficial strain.
On the other hand, the physiological character of these plasmodomous
monera is especially important, as it gives us the simple key to the
solution of the great question of spontaneous generation (or archigony,
_cf._ chapter xv.).

The chromacea are to-day found in every part of the earth, living
sometimes in fresh water and sometimes in the sea. Many species form
blue-green, violet, or reddish deposits on rocks, stones, wood, and
other objects. In these thin gelatinous plates millions of small
homogeneous cytodes are packed close together. Their tint is due to a
peculiar coloring matter (phycocyan), which is chemically connected
with the substance of the plasma-particle. The shade of this color
differs a good deal in the various species of chromacea (of which more
than eight hundred have been distinguished); in the native species it
is generally blue-green or sage-green, sometimes blue, cyanine blue,
or violet. Hence the common name cyanophyceæ (_i.e._, blue algæ).
It is incorrect, for two reasons; firstly, because only a part of
these protophyta are blue, and, secondly, because they (as simple,
primitive plants without tissue) must be distinguished from the real
algæ (phyceæ), which are multicellular, tissue-forming plants. Other
chromacea are red, orange, or yellow in color, as the interesting
_trichodesmium erythræum_, for instance, the flaky masses of which,
gathering in enormous quantities, cause at certain times the yellow
or red coloring of the sea-water in the tropics; it is these that are
responsible for the name "Red Sea" on the Arabian and "Yellow Sea" on
the Chinese coast. When I passed the equator in the Sunda Straits on
March 10, 1901, the boat sailed through colossal accumulations, several
miles in width, of this trichodesmium. The yellow or reddish surface of
the water looked as if it were strewn with sawdust. In the same way,
the surface of the Arctic Ocean is often colored brown or reddish-brown
by masses of the brown _procytella primordialis_ (formerly described as
_protococcus marinus_).

It is clearly quite illogical to regard the chromacea as a class
or family of the algæ, as is still done in most manuals of botany.
The real algæ--excluding the unicellular diatomes and paulotomes,
which belong to the protophyta--are multicellular plants that form
a _thallus_ or bed of a certain form and characteristic tissue. The
chromacea, which have not advanced as far as the real nucleated cell,
are unnucleated cytodes of a lower and earlier stage of plant-life.
If one would compare the chromacea with algæ or other plants at all,
the comparison cannot be with their constituent cells, but merely
with the chromatophora or chromatella, which are found in all green
plant-cells, and form _part_ of their contents. To be more precise,
these green granules of chlorophyll must be regarded as organella of
the plant-cell, or separated plasma-formations which arise beside the
nucleus in the cytoplasm. In the embryonic cells of the germs of plants
and in their vegetation points the chromatophora are as yet colorless,
and are developed, as solid, very refractive, globular, or roundish
granules, from the firm layer of plasm which immediately surrounds the
nucleus. Afterwards they are converted, by a chemical process, into
the green chlorophyll granules or chloroplasts, which have the most
important function in the plasmodomism or carbon-assimilation of the
plant.

The fact that the green chlorophyll granules grow independently
within the living plant-cell and multiply by segmentation is very
important and interesting. The globular chloroplasts are constricted
in the middle, and split into two equal daughter-globules. These
daughter-plastids grow, and multiply in turn in the same way. Hence
they behave within the plant-cell just like the free-living chromacea
in the water. On the strength of this significant comparison, one of
our ablest and most open-minded scientists, Fritz Müller-Desterro, of
Brazil, pointed out in 1893 that we may see in every green vegetal cell
a symbiosis between plasmodomous green and plasmophagous not-green
companions (_cf._ my _Anthropogeny_, figs. 277 and 278, and in the
text).

Many species of the simplest chromacea live as monobia (individually).
When the tiny plasma globules have split into two equal halves by
simple segmentation, they separate, and live their lives apart. This
is the case with the common, ubiquitous chroococcus. However, most
species live in common, the plasma granules forming more or less thick
cœnobia, or communities or colonies of cells. In the simplest case
(_aphanocapsa_) the social cytodes secrete a structureless gelatinous
mass, in which numbers of blue-green plasma globules are irregularly
distributed. In the _glœocapsa_, which forms a thin blue-green
gelatinous deposit on damp walls and rocks, the constituent cytodes
cover themselves immediately after cleavage with a fresh gelatinous
envelope, and these run together into large masses. But the majority
of the chromacea form firm, threadlike cell communities or chains
of plastids (catenal cœnobia.) As the transverse cleavage of the
rapidly multiplying cytodes always follows the same direction, and
the new daughter-cytodes remain joined at the cleavage surfaces, and
are flattened into discoid shape, we get stringlike formations or
articulated threads of considerable length, as in the oscillaria and
nostochina. When a number of these threads are joined together in
gelatinous masses, we often get large, irregular, jelly-like bodies, as
in the common "shooting-star jellies" (_nostoc communis_). They attain
the size of a plum.

In view of the extreme importance which I attach to the chromacea as
the earliest and simplest of all organisms, it is necessary to put
clearly the following facts with regard to their anatomic structure and
physiological activity:

1. The organism of the simplest chromacea is _not_ composed of
different organella or organs; and it shows no trace of purposive
construction or definite architecture.

2. The homogeneous tinted plasma granule which makes up the entire
organism in the simplest case (_chroococcus_) exhibits no plasma
structure (honeycomb, threads, etc.) whatever.

3. The original globular form of the plasma particle is the simplest of
all fundamental types, and is also that assumed by the inorganic body
(such as a drop of rain) in a condition of stable equilibrium.

4. The formation of a thin membrane at the surface of the structureless
plasma granule may be explained as a purely physical process--that of
surface strain.

5. The gelatinous envelope which is secreted by many of the chromacea
is also formed by a simple physical (or chemical) process.

6. The sole essential vital function that is common to all the
chromacea is self-maintenance, and growth by means of their vegetal
metabolism, or plasmodomism (=carbon assimilation); this purely
chemical process is on a level with the catalysis of inorganic
compounds (chapter x.).

7. The growth of the cytodes, in virtue of their continuous
plasmodomism, is on a level with the physical process of crystal growth.

8. The reproduction of the chromacea by simple cleavage is merely the
continuation of this simple growth process, when it passes the limit of
individual size.

9. All the other vital phenomena which are to be seen in some of the
chromacea can also be explained by physical or chemical causes on
mechanical principles. Not a single fact compels us to assume a "vital
force."

Especially noteworthy in regard to the physiological character of these
lowest organisms are their bionomic peculiarities, especially the
indifference to external influences, higher and lower temperatures,
etc. Many of the chromacea live in hot springs, with a temperature
of fifty to eighty degrees centigrade, in which no other organism is
found. Other species may remain for a long time frozen in ice, and
resume their vital activity as soon as it thaws. Many chromacea may be
completely dried up, and then resume their life if put in water after
several years.

Next in order to the chromacea we have the bacteria, the remarkable
little organisms which have been well known in the last few decades
as the causes of fatal diseases, and the agents of fermentation,
putrefaction, etc. The special science which is concerned with
them--modern bacteriology--has attained so important a position in
a short period--especially as regards practical and theoretical
medicine--that it is now represented by separate chairs at most of
the universities. We may admire the penetration and the perseverance
with which scientists have succeeded, with the aid of the best modern
microscopes and methods of preparation and coloring, in making so
close a study of the organism of the bacteria, determining their
physiological properties, and explaining their great importance for
organic life by careful experiments and methods of culture. The
bionomic or economic position of the bacteria in nature's household
has thus secured for these tiny organisms the greatest scientific and
practical interest.

However, we find that certain general views have been maintained by
specialists in bacteriology up to our own time which are in curious
contrast with these brilliant results. The biologist who studies the
systematic relations of the bacteria from the modern point of view of
the theory of descent is bewildered at the extraordinary views as to
the place of the bacteria in the plant-world (as segmentation-fungi),
their relations to other classes of plants, and the formation of their
species. When we carefully consider the morphological properties that
are common to all true bacteria and compare them with other organisms,
we are forced to the conclusion that I urged years ago in various
writings: the bacteria are not real (nucleated) cells, but unnucleated
cytodes of the rank of the monera; they are not real (tissue-forming)
fungi, but simple protists; their nearest relatives are the chromacea.

The individual organisms of the simplest kind, which bacteriologists
call "bacteria-cells," are not real nucleated cells. That is the clear
negative result of a number of most careful investigations which
have been made up to date with the object of finding a nucleus in
the plasma-body of the bacteria. Among recent exact investigations
we must especially note those of the botanist Reinke, of Kiel, who
sought in vain to detect a nucleus in one of the largest and most
easily studied genera of the bacteria, the _beggiatoa_, using every
modern technical aid. His conviction that this important cell-structure
is really lacking is the more valuable, as it is very prejudicial
to his own theory of "dominants." Other scientists (especially
Schaudinn) have recently claimed, as equivalent to a nucleus in some
of the larger bacteria, a number of very small granules, which are
irregularly distributed in the plasm, and are strongly tinted under
certain coloring processes. But even if the chemical identity of these
substances which take the same color were proved--which is certainly
not the case--and even if the appearance of scattered nuclein-granules
in the plasm could be regarded as a preliminary to, or a beginning
of, the differentiation of an individual, morphologically distinct
nucleus, we should not yet have shown its independence as an organellum
of the cell.

Nor is this any more proved from the circumstance that in some bacteria
(not all) we find a severance of the plasm into an inner and outer
layer, or a frothy structure with vacuole-formation, or a special
sharply outlined membrane on the plastid. Many bacteria (but not all)
have such a membrane, like the nearly related chromacea, and also the
secretion of a gelatine envelope. Both classes have also in common
an exclusively monogenetic reproduction. The bacteria multiply, like
the chromacea, by simple segmentation; as soon as the structureless
plasma-granule has reached a certain size by simple growth, it is
constricted and splits into two halves. In the long-bodied bacteria
(the rod-shaped bacilli) the constriction always goes through the
middle of the long axis, and is, therefore, simple transverse cleavage.
Many bacteria have also been said to multiply by the formation of
spores. But these so-called "spores" are really permanent quiescent
forms (without any multiplication of individuals); the central part
of the plastid (endoplasm) condenses, separates from the peripheral
part (exoplasm), and undergoes a chemical change which makes it very
indifferent to external influences (such as a high temperature).

The great majority of the bacteria differ so little morphologically
from the chromacea that we can only distinguish these two classes
of monera by the difference in their metabolism. The chromacea,
as protophyta, are plasmodomous. They form new plasm by synthesis
and reduction from simple inorganic compounds--water, carbonic
acid, ammonia, nitric acid, etc. But the bacteria, as protozoa, are
plasmophagous. They cannot, as a rule, form new plasm, but have to
take it from other organisms (as parasites, saprophytes, etc.);
they decompose it by analysis and oxydation. Hence the colorless
bacteria are without the important green, blue, or red coloring matter
(phycocyan) which tints the plastids of the chromacea, and is the real
instrument of the carbon-assimilation. However, there are exceptions
in this respect: _bacillus virens_ is tinted green with chlorophyll,
_micrococcus prodigiosus_ is blood-red, other bacteria purple, and
so on. Certain earth-dwelling bacteria (_nitro-bacteria_) have the
vegetal property of plasmodomism; they convert ammonia by oxydation
into nitrous acid, and this into nitric acid, using as their source of
carbon the carbonic acid gas in the atmosphere. They are thus quite
independent of organic substances, and feed, like the chromacea, on
simple inorganic compounds.

Hence the affinity between the plasmodomous chromacea and plasmophagous
bacteria is so close that it is impossible to give a single safe
criterion that will effectually separate the two classes. Many
botanists accordingly combine both groups in a single class with the
name of _schizophyta_, and within this distinguish as "orders" the
blue-green chromacea as _schizophycæ_ (cleavage-algæ) and the colorless
bacteria as _schizomycetes_ (cleavage-fungi). However, we must not
take this division too rigidly; and the absolute lack of a nucleus
and tissue-formation separates the chromacea just as widely from the
multicellular tissue-forming algæ as the bacteria from the fungi. The
simple multiplication by the halving of the cell, which is expressed in
the name "cleavage-plants" (_schizophyta_), is also found in many other
protists.

The number of forms that can be distinguished as species in the
technical sense is very great in the case of the bacteria, in
spite of the extreme simplicity of their outward appearance; many
biologists speak of several hundred, and even of more than a thousand,
species. But when we look solely to the outer form of the living
plasma-granule, we can only distinguish three fundamental types: (1)
Micrococci, or spherobacteria (briefly, cocci), globular or ellipsoid;
(2) bacilli, or rhabdo-bacteria (also called eubacteria, or bacteria in
the narrower sense), rod-shaped, cylindrical, and often twisted like
worms (comma-bacilli); (3) spirilla, or spirobacteria, screw-shaped
rods (vibriones when the screw is slight, and spirochæta when it
has many coils). Besides this threefold difference in the forms of
the cytodes, we have a ground of distinction in many bacilli and
spirilla in the possession of one or more very thin lashes (flagella),
which proceed from one of both poles of the lengthened plastid. The
construction and vibration of these serves for locomotion in the
swimming bacteria; but they are only found for a time in many species,
and in many others are altogether wanting.

Since, then, neither the simple outer form of the bacterium-cytodes
nor their homogeneous internal structure provides a satisfactory
ground for the systematic distinction of the numerous species,
their physiological properties are generally used for the purpose,
especially their different behavior towards organic foods (albumin,
gelatine, etc.), their chemical actions, and the various effects of
poisoning and decomposition which they produce in the living organism.
No bacteriologist now doubts that all the vital activities of the
bacteria are of a chemical nature, and precisely on this account
these microbes are of extreme importance. When we bear in mind how
complicated are the relations of the various species of bacteria to
the tissues of the human body, in which they cause the diseases of
typhus, hypochondriasis, cholera, and tuberculosis, we are bound to
admit that the real cause of these maladies must be sought in the
peculiar molecular structure of the bacterium-plasm, or the particular
arrangement of its molecules and the innumerable atoms (more than a
thousand) which are, in a very loose way, made up into special groups
of molecules. The chemical products of their mutual action are what we
call ptomaines, which are partly very virulent poisons (toxins). We
have succeeded in producing several of these poisonous matters in large
quantities by artificial culture, and isolating them and experimentally
ascertaining their nature; as, for instance, tetanin, which causes
tetanus, typhotoxin, the poison of typhus, etc.

In thus declaring the action of bacteria to be purely chemical and
analogous to that of well-known inorganic poisons, I would particularly
point out that this very justifiable statement is a pure hypothesis;
it is an excellent illustration of the fact that we cannot get on
in the explanation of the most important natural phenomena without
hypotheses. We can see nothing whatever of the chemical molecular
structure of the plasm, even under the highest power of the microscope;
it lies far below the limit of microscopic perception. Nevertheless,
no expert scientist has the slightest doubt of its existence, or that
the complicated movements of the sensitive atoms and the molecules and
groups of molecules they make up are the causes of the vast changes
which these tiny organisms effect in the tissues of the human and the
higher animal body.

Moreover, the distinction of the many species of bacteria is of
interest in connection with the general question of the nature and
constancy of a species. Whereas formerly in biological classification
only definite morphological characters, or definable differences in
outer form or inner structure, were regarded as of any moment in the
distinction of species, here, in view of the vagueness or total lack
of these characters, we have to look mainly to the physiological
properties, and these are based on the chemical differences in their
hypothetical molecular structure. But even these are not absolutely
constant; on the contrary, many bacteria lose their specific qualities
by progressive culture under changed food-conditions. By a change in
the temperature and the nutritive field in which a number of poisonous
bacteria have been reared, or by the action of certain chemicals, not
only the growth and multiplication are altered, but also the injurious
effect they have on other organisms by the generation of poisons.
This poisonous effect is weakened, and--what is most important--the
weakening is transmitted by heredity to the following generations. On
this is based the familiar process of inoculation, an admirable example
of the inheritance of acquired characteristics.

As the bacteria are still often described as "cleavage-fungi" and
classified along with the real fungi, we must particularly point
out the wide gulf that separates the two groups. The real fungi (or
_mycetes_) are metaphyta, their multicellular body (_thallus_) forming
a very characteristic sort of tissue, the mycelium; this is composed
of a number of interlaced and interwoven threads (or hyphens). Each
fungus-thread consists of a row of lengthened cells, which have a thin
membrane and enclose a number of small nuclei in the colorless plasm.
Moreover, the two sub-classes of the real fungi, the ascomycetes and
basimycetes, form peculiar fruit-bodies which generate spores (ascodia
and basidia). There is no trace whatever of these real characteristics
of the true fungus in the bacteria. Nor is it less incorrect to class
them with the fungilli, the so-called unicellular fungi or phycomycetes
(ovomycetes and zygomycetes); these form a special class of protists
which has the closest affinity to the gregarinæ.

Like the closely related chromacea, many of the bacteria show a marked
tendency to form communities or cell-colonies. These cell-communities
arise, as elsewhere, from the fact that the individuals, which
multiply rapidly by continuous cleavage, remain joined together.
This may happen in two ways. When the social bacteria secrete large
quantities of gelatine, and remain distributed in this, we have the
_zooglœa_ (as in the case of the _aphanocapsa_ and _glœocapsa_
among the chromacea). If, on the other hand, the long-bodied
bacilli remain fastened together in rows, we get the knotted
threads of _leptothrix_ and _beggiatoa_ (which may be compared with
the oscillaria). And, if these threads go into branches, we have
_cladothrix_. Other cœnobia of bacteria have the appearance of
disks, the cytodes dividing in a plane, usually in groups of four (as
in _merismopedia_), or of cube-shaped packets when they are in all
three directions of space (_sarcina_).

The two classes of bacteria and chromacea seem, in the present
condition of our knowledge, on account of their simple organization,
to be the simplest of all living things, real monera, or organisms
without organs. Hence we have to put them at the lowest stage of
the protist kingdom, and must regard the difference between them
and the most highly differentiated unicellular beings (such as the
radiolaria, ciliated infusoria, diatomes, or siphonea) as no smaller
than the difference (in the realm of the histona) between a lower
polyp (_hydra_) and a vertebrate, or between a simple alga (_ulva_)
and a palm. But if the kingdom of the protists is badly divided, on
the older rule, into a plant kingdom and an animal kingdom, the only
discriminating mark we have left is the difference in metabolism; in
that case we have to include the plasmophagous bacteria in the animal
kingdom (as Ehrenberg did in 1838) and the plasmodomous chromacea
in the plant kingdom. The remarkable class of the flagellata, which
includes ciliated unicellulars of both groups, contains several
forms which are only distinguished from the typical bacterium by the
possession of a nucleus. If it is true that in some of the protists
which were counted as bacteria a real nucleus has been detected, these
must be separated from the others (unnucleated) and included in the
nucleated flagellata.

The monera which I described in 1866, and on which I based the theory
of the monera in my monograph, belong to a different division of the
protists from the classes of bacteria and chromacea. These are the
forms which I described as _protamœba_, _protogenes_, _protomyxa_,
etc. Their naked mobile plasma-bodies thrust out pseudopodia, or
variable "false feet," from their surface, like the (nucleated) real
rhizopods (=sarcodinæ); but they differ essentially from the latter in
the absence of a nucleus. Afterwards (in my _Systematic Phytogeny_)
I proposed to separate these unnucleated rhizopods from the others,
giving the name of _lobomonera_ (_protamœba_) to the amœba-like
monera with flap-shaped feet, and the name of _rhizomonera_
(_protomyxa_, _pontomyxa_, _biomyxa_, _arachnula_, etc.) to the
gromia-like, root-feet forming monera. However, of late years, real
nuclei have been detected in each of these large monera, and so they
have been proved to be true cells. This discovery was made possible by
the improved modern methods of coloring the nucleus which I had not the
use of thirty years ago in my first observations. On the strength of
these recent discoveries many scientists claim that all the monera I
described are true cells, and must have nuclei. This baseless assertion
is much employed by the opponents of the theory of evolution in order
to deny the existence of the monera altogether.

Of the genus of monera which we call protamœba I have given an
illustration in my _History of Creation_ (tenth edition), which has
been frequently reproduced. Several species (at least two or three)
of this genus still exist, and are distinguished by the shape of
their flap-formation and their method of motion. They resemble
ordinary simple amœbæ, and only differ from these to any extent
in the absence of a nucleus. The _protamœba primitiva_ seems
to be pretty widely distributed; it has been found repeatedly by
observers (Gruber, Cienkowski, Leidy, etc.) in inland waters. In the
zoological demonstrations which I have given at the University of Jena
for forty years, and in the course of which the lowly inhabitants
of our fresh water are regularly examined with the microscope, the
_protamœba primitiva_ has been found four or five times. It
always had the same form, as I described it, moved about by the slow
formation of flaps at its surface, multiplied by simple cleavage,
and showed no trace of a nucleus in its homogeneous plasma-body even
with the most careful application of the modern methods of tinting
the nucleus. A larger number of very fine granules (microsoma) that
were irregularly distributed in the plasm, and were more or less
colored by nucleus-reagents, cannot be reckoned as clear equivalents
of the nucleus in this or in similar cases; they are probably products
of metabolism. The same may be said of the larger marine form of
rhizomoneron, which A. Gruber has recently called _pelomyxa pallida_.

The large marine form of rhizomoneron to which Huxley gave the name
of _bathybius Haeckelii_ in 1868, and as to the real nature of which
many opinions have been expressed, seems, according to the latest
investigation, not to have the significance ascribed to it. However,
the much-discussed question of the bathybius is superfluous as far as
our monera theory and the associated hypothesis of archigony (chapter
xv.) are concerned, since we have now a better knowledge of the much
more important monera-forms of the chromacea and bacteria.

In the case of some of the protists I described in my _Monograph on the
Monera_, it is at present doubtful whether their plasma-body contains
a nucleus or not, and, therefore, whether they are to be classed as
true cells or cytodes. This applies especially to the forms which
only happened to come under observation once, such as _protomyxa_
and _myxastrum_. In these obscure cases we must wait for fresh
investigations and the application of the modern methods of tinting
the nucleus. I may, however, point out, in passing, that these famous
methods of nucleus-coloring give by no means the absolute certainty
which is ascribed to them; there are other substances which take color
in the same way as chromatin. As far as my monera theory is concerned,
or the great general importance which I attach to these unnucleated
living granules of plasm, it does not matter whether a nucleus is
detected in these problematic monera or not. The chromacea alone--the
most important of all monera--completely suffice to provide a base for
the far-reaching theoretical conclusions which I draw from it.

At the close of these observations on the monera I will briefly
recapitulate the weighty inferences which we can deduce from their
simple organization. They serve as a solid foundation for the chief
theses of our monistic biology; and they are inconsistent with the
dualistic views of modern vitalists. In the first place, I emphasize
the fact that the structureless plasm-body of the simple monera has
no sort of organization and no composition from dissimilar parts
co-operating for definite vital aims. Reinke's conscious "dominant"--as
well as Weismann's mechanical "determinants"--have nothing to do here.
The whole vital activity of the simplest monera, especially of the
chromacea, is confined to their metabolism, and is therefore a purely
chemical process, that may be compared to the catalysis of inorganic
compounds. The simple formation of individuals in this primitive living
matter is merely a question of the cleavage of plasma globules of a
certain size (_chroococcus_); and their primitive multiplication (by
simple self-division) is only a continued growth (analogous to that
of the crystal). When this simple growth passes a certain limit, that
is fixed by the chemical constitution, it leads to the independent
existence of the redundant growth-products.




X

NUTRITION

 Functions of nutrition--Assimilation and disassimilation--Plasmodoma
 and plasmophaga--Phytoplasm and zooplasm--Plasmodomism of
 plants--Chlorophyll granules and nitro-bacteria--Plasmophagism of
 fungi and animals--Metasitism (conversion of metabolism)--Nutrition
 of the monera (chromacea, bacteria, rhizomonera)--Nutrition of the
 protophyta and metaphyta (cell-plants and tissue-plants)--Nutrition
 of the metazoa--- Gastræa theory--Gastro-canal system of the
 cœlenteria (gastræads, sponges, cnidaria, platodes)--Nutrition
 of the cœlomaria (digestion, circulation, respiration,
 evacuation)--Saprositism--Parasitism--Symbiosis.


The wonder of life which we call, in the widest sense of the word,
"nutrition" is the chief factor in the self-maintenance of the organic
individual. It is always bound up with a chemical modification of the
living matter, an organic metabolism (circulation of matter), and a
corresponding circulation of force. In this chemical process plasm is
used up, built up afresh, and once more disintegrated. The metabolism
which lies at the root of this chemistry of food is the essential
feature in the manifold processes of nutrition. A large part of the
several nutritive processes are explained without further trouble
by the known physical and chemical properties of inorganic bodies;
for another part of them we have not yet succeeded in doing this.
Nevertheless, all impartial physiologists now agree that it is possible
in principle, and that we have no reason to introduce a special vital
principle. All the trophic (nutritive) processes, without exception,
are subject to the law of substance.

In all the higher plants and animals the chemical process of
metabolism, with the stream of energy that accompanies it, is a very
complex vital activity, in which many different functions and organs
co-operate with the common aim of self-maintenance. As a rule, they are
distributed in four groups--namely: (1) Intussusception of food and
digestion: (2) distribution of the food in the body, or circulation;
(3) respiration, or exchange of gases; and (4) excretion of unusable
matter. In most of the histona, either tissue-plants or tissue-animals,
a number of organs are differentiated for the accomplishment of these
tasks. At the lower stages of life this division of labor is not found,
the entire process of nutrition being accomplished by a single layer of
cells (lower algæ, gastræads, sponges, lower polyps). In the protists,
again, it is the single cell that does all these things itself; in the
simplest cases, the monera, a homogeneous plasma-globule. As a long
gradation uninterruptedly unites these lowest forms of nutrition with
the more complicated forms, we must regard the latter no less than the
former as physico-chemical processes.

When we take the whole of the metabolic functions in organisms
together, we may look upon them as the outcome of two opposite chemical
processes--on the one hand the building-up of living matter by taking
in food (assimilation), and on the other the breaking-down of it in
consequence of its vital activity (disassimilation). As in every case
the plasm is the active living matter, we may say: _Assimilation_ (or
plasma-production) consists in the conversion within the organism into
the special plasm of the particular species of food that has been
received from without; _disassimilation_ (or plasma-destruction)
is the result of the work done by the plasm, which is the cause of
its partial decomposition or breakdown. In both respects there is a
striking difference between the two great kingdoms of organic nature.
The plant kingdom is, on the whole, the agent of assimilation, forming
new plasm by synthesis and reduction from inorganic matter. In the
animal world, on the contrary, disassimilation preponderates, the plasm
received being resolved by oxydation, and the actual energy taken out
of it by analysis being converted into heat and motion. Plants are
plasmodomous; animals, plasmophagous.

Of all the chemical processes the most important, because the most
indispensable, for the origin and maintenance of organic life is the
constant reconstruction of plasm. We give it the name of plasmodomism
(_domeo_=to build up), or carbon-assimilation. Botanists have the
habit of late of calling it briefly assimilation, and have thus
caused a good deal of misunderstanding. The more common and older
meaning of assimilation in animal physiology is, in the widest sense,
the intussusception and preparation of the food received. But the
carbon-assimilation in plants--what I call plasmodomism--is only the
first and original form of plasma-production. It means that the plant
is able, under the influence of sunlight, to form carbohydrates,
and from these new plasm, out of simple inorganic compounds (water,
carbonic acid, nitric acid, and ammonia) by synthesis and reduction.
The animal is unable to do this. It has to take its plasm in its
food from other organisms--plant-eaters directly, and animal-eaters
indirectly. We therefore give the title of _plasmophagous_ to these
animal "plasma-eaters." In working up the foreign plasm it has eaten,
and converting it into its own specific form of plasm, the animal
also accomplishes assimilation; but this animal albumin-assimilation
is totally different from the vegetal carbon-assimilation. The
fresh-formed animal plasm is then broken up by oxydation, and by this
analysis the energy needed for the vital movements is obtained.

The physiological contrast which we thus find between the two principal
forms of living matter, the synthetic plasm of the plant and the
analytic plasm of the animal, is of great importance for the lasting
maintenance of the whole organic world. It depends on a reversal of
the molecular movement in the plasm, the intimate nature of which is
just as little known to us as the chemical constitution of the albumins
in general, and that of living albumin, the plasm, in particular. As
I mentioned in chapter v., modern physiological chemistry has good
reason to believe that the invisible albumin-molecule is, comparatively
speaking, gigantic, and is composed of more than a thousand atoms.
These are in such an unstable equilibrium, so complicated and
impermanent an arrangement, that the slightest push or stimulus
suffices to alter them and form a new kind of plasm. As a fact, the
number and variety of kinds of plasm are immense. This is seen at
once from the ontogenetic fact that the ovum and sperm-cell of each
species (and each variety) have a specific chemical constitution.
In reproduction this is transmitted to the offspring. But, setting
aside these countless finer modifications, we may distinguish two
chief groups of kinds of plasm: the phytoplasm of the plant, with the
synthetic property of plasmodomism, and the zooplasm of the animal,
which is destitute of this property, and so confined to plasmophagy.

The remarkable synthetic process of building up the plasm, to which
we give the name of plasmodomism, or carbon-assimilation, usually
needs as its first condition the radiant energy of sunlight. Every
green plant-cell contains in its chlorophyll-granules so many tiny
laboratories, their green plasm being able to form new plasm out of
inorganic compounds under the influence of light. The water that is
needed for this, besides nitrogenous compounds (nitric acid, ammonia),
is drawn from the earth by the roots; the carbonic acid is taken from
the atmosphere by the green leaves. The immediate products of the
synthesis, due to the separation of the carbonic acid, is, as a rule, a
non-nitrogenous starch-flour (_amylum_). This is further used for the
composition of the nitrogenous albumin by an as yet unknown synthetic
process, with the aid of nitrogenous mineral compounds. In this process
of reduction the separated free oxygen is returned to the atmosphere.
The carbohydrates that chiefly co-operate in this are glucoses and
maltoses: the mineral substances, especially salts of potassium and
magnesium, and compounds of these elements with nitric acid, sulphuric
acid, and phosphoric acid. Iron is also found to be an important
element in the process, though in a very small quantity. As a rule,
the ferruginous chlorophyll can only form new plasm with the help of
light-waves. The most important part of the spectrum for this purpose
is that containing the red, orange, and yellow waves.

The chief factor in plasma-formation in the organic world is the
photosynthesis, or ordinary carbon-assimilation by chlorophyll, the
wonderful green matter that amounts to only a very small percentage
(about one-tenth) of the weight of the chlorophyll-granules, and can
be separated from their plasmatic substance by certain methods. Even
when the plant has some other color than green the chlorophyll is still
the real plasmodomous substance. Its green color is then masked by
some other color--diatomin in the yellow diatomes, phycorhodin in the
red rhodophyceæ, phycophæin in the brown phæophyceæ, and phyocyan in
the blue-green chromacea or cyanophyceæ. The latter have an especial
interest for us, because in the simplest specimens the entire organism
is merely a globular bluish-green granule of plasm. Moreover, in the
simplest forms of nucleated primitive plants (_algariæ_)--many of the
so-called unicellular algæ--the metabolism is effected by a single
grain of chlorophyll. There is usually a large number of them in the
plasm of the plant-cells.

Another kind of plasm-synthesis, quite different from the ordinary
plasmodomism by chlorophyll and sunlight has lately been discovered in
some of the lowest organisms (by Heraeus, Winogradsky, and others). The
nitro-bacteria (or nitromonades) are tiny monera (unnucleated cells)
that live in complete darkness underground. Their globular colorless
plasma-bodies contain neither chlorophyll nor nucleus. They have the
remarkable capacity of forming carbohydrates, and from these plasm,
by a peculiar synthesis out of purely inorganic compounds--water,
carbonic acid, ammonia, and nitric acid. Pfeffer has called this
carbon-assimilation, on account of its purely chemical nature,
"chemosynthesis," in opposition to the ordinary photosynthesis by
means of sunlight. There are also other bacteria (sulphur-bacteria,
purple-bacteria, etc.) that show various peculiarities of metabolism.
The nitro-bacteria must belong to the oldest monera, and represent a
transition from the vegetal chromacea to the animal bacteria.

The extensive class of the fungi (or _mycetes_) resembles a part of
the bacteria in regard to metabolism. These organisms are, it is true,
generally regarded as plants, but they have not the capacity of the
green, chlorophyll-bearing plants to supply themselves with carbon
from the carbonic acid in the atmosphere. They have to take it from
organic substances, such as albumin, carbohydrates, etc., like the
animals. But while the animals have to derive their nitrogen from the
latter, the fungi can obtain it from inorganic matter in the earth.
Fungi cannot support life without the addition of organic compounds;
but we can make them grow in a food solution consisting of sugar and
purely inorganic nitrogenous salts. Thus they are on the border that
separates the plasmodomous plants from the plasmophagous animals. Like
the latter, the fungi have evolved from the plants through changed food
conditions. We find this process even among the unicellular protists in
the phycomycetes, which descend from the siphonea. In the same way the
real multicellular fungi (ascomycetes and basimycetes) may be traced to
the tissue-forming algæ.

All true animals have to derive their food from the plant kingdom, the
vegetal feeders directly, and the flesh feeders indirectly, when they
consume vegetal feeders. Hence the animals are, in a certain sense, as
the older natural philosophy put it four hundred years ago, "parasites
of the plant world." From the point of view of phylogeny, the animal
kingdom is, therefore, clearly much younger than the plant kingdom. The
development of the animals from the plants was determined originally by
a change in the method of nutrition which we call metasitism.

The chemical modification of the living matter which is connected
with the loss of plasmodomism--in other words, the conversion of the
reducing phytoplasm into oxidizing zooplasm--must be regarded as
one of the most important changes in the history of organic life.
This "reversal of metabolism" is polyphyletic; it has been repeated
many times in the course of biological history, and has taken place
independently in very different groups of the organic world--whenever
a plasmodomous cell or group of cells (=tissue) had occasion to feed
directly on ready-made plasm, instead of giving itself the trouble of
building it up out of inorganic compounds. We see this particularly
among the unicellular protists in the independent ciliated cells.
The longer plasmophagous flagellata, which are colorless, and have
no chlorophyll (monodina, conoflagellata), closely resemble in
form and movement the older plasmadomous and chlorophyll-bearing
mastigota, from which they are descended (volvocina, peridinia); they
only differ in the manner of nutrition. The colorless flagellata
feed on ready-formed plasm, which they obtain either by means of
their lashes or by a special cell mouth in their cell body. On the
other hand, their ancestors, the green or yellow mastigota, form
new plasm by photosynthesis like true cells. But there are also
complete intermediate forms between the two groups--for instance, the
chrysomonades and the gymnodinia; these may behave alternately as
protozoa or protophyta. In the same way we can derive the phycomycetes
by metasitism from the siphonea, the fungi from the algæ; and, finally,
the process is also found in many of the higher parasitic plants
(orchids, orobanches, etc.). (See under "Parasitism.")

As is the case with every other vital function, so for the function
of metabolism we find a starting-point in the lowest and simplest
group of the protophyta, the chromacea. In their oldest forms, the
chroococcacea, the whole body is merely a blue-green, structureless,
globular plasma particle, growing by means of its plasmodomous power,
and splitting up as soon as it reaches a certain stage of growth.
There the miracle of life consists merely of the chemical process of
plasmodomism by photosynthesis. The sunlight enables the blue-green
phytoplasm to form new plasm of the same kind out of inorganic
compounds (water, carbonic acid, ammonia, and nitric acid). We may look
upon this process as a special kind of catalysis. In this case there
is absolutely nothing to be done by Reinke's "dominants," or conscious
and purposive vital forces. There are, as yet, no differentiated
physiological functions in these organisms without organs, and no
anatomically distinct members; and so their one vital activity, growth,
may very well be compared to the simple growth of inorganic crystals.

It has been pointed out repeatedly that the remarkable monera which
now play so important a part in biology as bacteria stand, in many
respects, quite apart from the ordinary vital phenomena of the
higher organisms. This is especially true of their metabolism, which
has the most striking peculiarities. Morphologically, many of the
bacteria cannot be distinguished from their nearest relatives and
direct ancestors, the chromacea, differing from them only in the
absence of coloring matter in the plasm. Many of them are simple,
globular, ellipsoid, or rod-shaped plasma particles, without any
visible organization or movement. Others move about by means of one or
more very fine lashes (like the flagellata). No real nucleus can be
discovered in the structureless plasma body. The very fine granules
which are found in some species, and the vacuole-formation that we see
in others, may be regarded as products of metabolism; and the same
may be said of the thin membrane or the thicker gelatinous envelope
which many of the bacteria secrete. This makes all the more remarkable
the peculiarity of their chemical constitution and the metabolism
determined thereby. The nitro-bacteria we have mentioned previously are
plasmodomous; the anaërobe bacteria (of butyric acid and tetanus) only
flourish where oxygen is excluded; the sulphur bacteria (_beggiatoa_)
secrete--by the oxydation of sulphuretted hydrogen--pure regulation
sulphur in the form of round granules. The ferruginous bacteria
(_leptothrix ochrocea_) store up oxyhydrate of iron (by the oxydation
of carbonic protoxide of iron). The saprogenetic bacteria cause
putrefaction, and the zymogenetic fermentation. Finally, we have the
very interesting pathogenetic bacteria which cause the most dangerous
diseases by the secretion of special poisons--toxins--festering,
small-pox, tetanus, diphtheria, typhus, tuberculosis, cholera, etc.
On account of their great practical importance, these bacteria have
of late been taken over by a special branch of biology, bacteriology.
But only a few of the many experts in this department have pointed out
the extreme theoretical significance which these zoomonera have for
the important questions of general biology. These structureless plasma
bodies show unmistakably that their vital activity is a purely chemical
phenomenon. Their great variety proves how manifold and complicated
must be the molecular composition of the plasm, even in these simplest
organisms.

The unicellular protophyta exhibit the same form of metabolism and
plasmodomism as the familiar green cells of the tissue-plants; but
in most of the protozoa we find special features of nutrition and
plasmophagy. The great class of the rhizopods is distinguished by the
fact that their naked plasma body can take in ready-formed solid food
at any point of its surface. On the other hand, most of the infusoria
have a definite mouth-opening in the outer wall of their unicellular
body, and sometimes a gullet-tube as well. Besides this cell-mouth
(_cytostoma_) we usually find also a second opening for the discharge
of indigestible matter, a cell-anus (_cytopyge_).

Metabolism in the tissue plants (metaphyta) forms a long gradation from
very simple to very complicated arrangements. The lowest and oldest
thallophyta, especially the simplest algæ, are not far removed from
the communities of protophyta, and, like these, are merely definitely
grouped colonies of cells. The social cells which form their most
rudimentary tissue are quite homogeneous, with no differentiation
beyond that of sex. The thallus or bed-formation consists in the
simplest specimens of plain or branched fine threads, consisting of
rows or chains of homogeneous cells (so _conferva_ among the green,
_ectocarpus_ among the brown, and _callithamnion_ among the red
algæ). Other algæ (such as the ulva) form thin leaf-shaped forms of
the thallus, a number of homogeneous cells lying side by side along a
level. In the larger algæ compact tissue-bodies are formed, in which
frequently firmer rows of cells exhibit the rudiments of fibres; and
the thallus divides, as in the cormophyta, into root, stalk, and
leaves. There is also a trophic differentiation, the fibres undertaking
special functions of nutrition (the conduction of the sap). The
same must be said of the mosses (_bryophyta_). Their lowest forms
(_ricciadinæ_) are close akin to the algæ; the highest mosses (the
_mnium_ and _polytrichum_, for instance) approach the cormophyta. Many
botanists comprise these lower plants--algæ, fungi, and mosses--under
the title of "cell-plants" (_cytophyta_), and oppose the higher
plants--ferns and flowering-plants--to them as "vascular plants"
(_angiophyta_), because they have complex fibres or sap vessels. This
distinction has a phylogenetic significance similar to the division
between cœlenteria and cœlomaria in the animal kingdom.

While most of the cell-plants either live in the water (algæ) or are
very simply organized on account of their saprophytic or parasitic
habits (fungi), the vascular plants mostly live on land, and have to
adapt themselves to much more complicated conditions. Their nutrition
is accordingly distributed among different functions, and special
organs have been evolved to discharge them. This is equally true of
the crytogam ferns (_pteridophyta_) and the phanerogam flowering
plants (_anthophyta_). The most important later acquisition which
distinguishes both groups from the lower cell-plants is the possession
of vascular or conducting fibres. These organs for conducting water
pass through the entire body of the vascular plant in the shape of
long tubes, formed by the combination of rows of cells; the cells
themselves die off, and their plasma content disappears. The stream of
water that rises constantly in these tubes is taken up by the roots,
conducted by the fibres to all parts, and given off (transpiration) by
the pores of the leaves. But these pores also serve for the breathing
of plants, being connected with the air-containing intercellular
passages; through these air-spaces, which serve for the aëration of
the higher plant-body, air and moisture can enter, and oxygen be given
off in respiration. Finally, many of the vascular plants have special
glands that serve for secretion (of oil, resin, etc.). In the higher
flowering plants this division of work among the various digestive
organs gives rise to a very complicated apparatus for nutrition. Among
the many remarkable structures that have been developed in this way by
adaptation to special conditions we may particularly note the organs
for catching and digesting insects in the insect-eating plants, the
European _drosera_ and _utricalaria_, and the tropical _nepenthas_ and
_dionæa_.

The long scale of evolutionary forms which we find in the tissue
animals (metazoa) leads up uninterruptedly from the simplest to
the most elaborate physiological functions and a corresponding
morphological complexity of organs. The two principal divisions of
the metazoa are chiefly distinguished by the circumstance that in the
cœlenteria one single system of organs, the gastro-canal system,
discharges the whole (or most part) of the partial functions of
nutrition; while in the cœlomaria they are usually distributed among
four different systems of organs, each of which is made up of a number
of organs. To an extent, we find once more in each great division
characteristic types of organization. However, comparative ontogeny
teaches us that all these various structures have been developed
from one simple fundamental form, as I have shown in my theory of the
gastræa (1872).

The older research into the origin of the nutritive apparatus in
the metazoa--especially its chief part, the alimentary or gastric
canal--had led to the erroneous belief that in several groups of the
metazoa it owed its origin to very different growth-processes, and
that particularly in the higher vertebrates (the amniotes) it was
a comparatively late product of evolution. On the other hand, the
comparative study of the embryology of the lower and higher animals
led me thirty-four years ago to the opposite conclusion, that a simple
gastric sac was the first and oldest organ of all the metazoa, and that
all the different forms of it had been developed from this primitive
type. I gave this view in my _Biology of the Sponges_ in 1872; and I
developed and established it in my _Studies of the Gastræa Theory_ in
1873. In the latter book I also worked out the important conclusions
that follow from this monistic reform of the theory of germinal layers
for the phylogenetic natural classification of the animal kingdom.
I began with the consideration of the simplest sponges (_olynthus_)
and cnidaria (_hydra_). The whole body of these lowest and oldest
of the cœlenteria is in essence nothing but a round, oval, or
cylindrical gastric vesicle, a digestive sac, the thin wall of which
consists of two simple layers of cells. The outer layer (the ectoderm
or skin-layer) is the covering layer of the external skin (epidermis);
it is the instrument of sensation and movement. The inner layer of
cells (entoderm or gastric layer) serves for nutrition; it clothes
the simple cavity of the sac, which admits the food by its opening
and digests it. This opening is the primitive mouth (_prostoma_ or
_blastoporus_), the inner cavity itself the primitive gut (_progaster_
or _archenteron_). I proved that there was the same composition in
the young embryos or larvæ of many of the lower animals, and showed
that the manifold and apparently very different embryonic form of all
the higher animals may be reduced to the same common type. To this I
gave the name of the "cup-embryo" or gastric larvæ (_gastrula_), and
concluded, in virtue of the biogenetic law, that it is the palingenetic
reproduction of a corresponding ancestral form (the _gastræa_)
maintained until the present by heredity. It was not until much later
(1895) that Monticelli discovered a modern gastræad (_pemmatodiscus_)
which corresponds completely to this hypothetical ancestor (see the
last edition of my _Anthropogeny_, fig. 287). The simplest living forms
of the sponges (_olynthus_) and the cnidaria (_hydra_) only differ from
this hypothetical primitive form of the gastræa by a few secondary and
subsequently acquired features.

The classes of the lower animals which we comprise under the name
cœlenteria (or cœlenterata in the widest sense) generally agree
in having all the functions of nutrition accomplished exclusively (or
for the most part) by a single system of organs, the gastro-canal or
gastro-vascular system. From their common stem-group, the gastræads,
three different stems have been evolved--the sponges, cnidaria, and
platodes. All these cœlenteria have three features in common: (1)
The gastric canal or tube has only one opening--the primitive mouth,
which serves at once for admitting food and ejecting indigestible
matter; there is no anus; (2) there is no special body-cavity
(_cœloma_) distinct from the gastric tube; (3) there is also no
trace of a vascular system. All cavities that are found in these lower
animals besides the digestive gut-cavity are direct processes from it
(with the exception of the nephridia in the platodes).

While the simple digestive gut is the sole organ of nutrition in the
stem-group of the gastræads, we find other structures co-operating in
the rest of the cœlenteria. The characteristic stem of the sponges
is distinguished by the piercing of the wall of the gastric vesicle
with several holes. Through these water pours into the body, bringing
with it the small particles of food which are received and digested
by the ciliated cells of the entoderm; the water emerges again by the
mouth-opening (_osculum_). The best-known of the sponges is the common
bath-sponge (_euspongia officinalis_), the horny skeleton of which
we use daily in washing. In these and most other sponges the large,
unshapely body is traversed by a number of branching canals, on which
there are thousands of tiny vesicles, produced by the multiplication
of a simple gastric vesicle of the primitive sponge (_olynthus_). Each
of these ciliated chambers is really a tiny gastræa, a "person" of the
simplest character (_cf._ chapter vii.). Hence we may regard the whole
sponge-body as a gastræad-stock (_cormus_).

The large group of the cnidaria offers a long series of evolutionary
stages, from very small and simple to very large and elaborate forms.
Some of them remain at a very low stage, as does our common green
fresh-water polyp (_hydra viridis_), which only differs from the
gastræa by a few variations in tissue and the formation of a crown of
feelers about the mouth. Most of the polyps form stocks (_cormi_),
the individuals shooting out buds which remain joined to the mother
animal. In these and all the other stock-forming animals the nutrition
is communistic; all the food that the individuals get and digest is
conducted by tubes to the common fund and equally distributed. In all
the larger cnidaria the body-wall becomes thicker, and is traversed by
branching gastro-canals; these convey the nutritive fluid to all parts
of the body.

While the fundamental type in the cnidaria is radial (determined
by the crown of radiating feelers or tentacles that surrounds the
mouth), it is bilateral-symmetrical in the platodes or "flat-worms"
(_plathelminthes_). In this animal-stem, moreover, the lowest forms,
the platodaria (also called _cryptocœla_ and _acæla_) come very
close to the gastræa. But most of the platodes are distinguished from
the rest of the cœlenteria by the formation of a pair of nephridia
(renal canals or water-vessels), thin tubes which, as excretory organs,
remove from the body the unusable products of metabolism, the urine.
Here we have a second organ of nutrition, the gut tube, added to the
first. In the lower platodes this remains very simple. As a rule, a
gullet tube (pharynx) is formed by the hollowing out of the mouth, as
in the corals; and as in the case of the latter branched canals, which
conduct the nutritive sap from the stomach to distant parts of the
body, grow out of the stomach, in the larger coil-worms (_turbellaria_)
and suction-worms (_trematodes_). On the other hand, the gut atrophies
in the tape-worms (_cestodes_); as these parasites live in the
intestines or other organs of animals, they can obtain their nutritive
sap directly from them through the surface of the skin.

The more highly organized cœlomaria differ from the simpler
cœlenteria chiefly by the greater complexity in the structure
and functions of their apparatus of nutrition. As a rule, these
functions are divided between four groups of organs, which are not yet
differentiated in the cœlenteria--namely: 1, organs of digestion
(gastric system); 2, organs of circulation (vascular system); 3, organs
of breathing (respiratory system); and 4, organs of excretion (renal
system). Moreover, in the cœlomaria the gastric canal has usually
two openings, the mouth and the anus. Finally, they all have a special
body-cavity (_cœloma_); this is quite separate from the gastric
canal, which is suspended in it, and serves for the formation of the
sexual cells. It is formed in the embryo by the hollowing out and
cutting off of a pair of sacs (cœlom-pouches) from the gut near the
mouth; the pouches touch, and then coalesce, as their division-walls
break down. If a part of the dividing wall remains, it serves as
mesentery to fasten the gut to the body-wall. The action of the four
groups of alimentary organs remains very simple in the lowest and
oldest cœlomaria, the worms (_vermalia_); but in the other higher
animals, which have been evolved from these, they have very varied and
often complicated features.

In the great majority of the cœlomaria the gastric system forms a
highly differentiated apparatus, composed, as in man, of a number of
different organs. The food is usually taken in by the mouth, ground
up by the jaws or the teeth, and softened with saliva, which the
salivary glands pour into the cavity of the mouth. From the mouth
the pulpy food passes in swallowing into the gullet, which often has
glandular appendages, and from this through the narrow esophagus into
the stomach. This most important part of the alimentary apparatus is
often divided into several sections, one of which (the masticating
stomach) is armed with teeth and prepared for a further triturition
of solid pieces, while the other (the glandular stomach) produces the
dissolving gastric juice. The liquefied food (_chylus_) then passes
into the small intestine (_ileum_), which has to absorb it, and is as a
rule the longest section of the alimentary canal. A number of different
digestive glands open into this intestine, the most important of them
being the liver. The small intestine is often sharply distinguished
from the large intestine (_colon_), the last large section of the
alimentary canal; into this also a number of glands and blind
intestines open. The last portion of it is called the _rectum_, and
this removes the indigestible remnants of the food (_fæces_) through
the anus.

This general plan of the alimentary system, which is common to most
of the cœlomaria in its chief features, is very much modified in
the various groups of these animals and adapted to their several
conditions of nutrition. The simplest structures are found in many of
the vermalia; the lowest forms of these, the rotifers, and especially
the gastrotricha, still closely resemble their platode ancestors, the
turbellaria. The higher type of animal-stems which have been evolved
from them are partly distinguished by special structures. Thus the
mollusks have a characteristic masticating apparatus; on their tongue
there is a hard plate (_radula_) armed with a number of teeth, which
grinds against a hard upper jaw, and so breaks up the food. In most of
the articulates this work is done by side-jaws, which consist of hard
rods and represent modified bones. The vertebrates and the closely
related tunicates are distinguished by the conversion of the first
sections of the alimentary canal into a characteristic respiratory
apparatus (gills). But the construction of the various sections of
the gastro-canal also varies a good deal in the small groups of
the cœlomaria, as it depends to a great extent on the nature of
the food and the conditions in which it is got and prepared. The
largest expenditure of mechanical and chemical energy is needed for
a voluminous solid vegetal diet. Hence the alimentary canal and its
many appendages are longest and most complicated in the plant-eating
snails, leaf-eating insects, and grass-eating ruminants. On the other
hand, they are shortest and simplest in parasitic cœlomaria, which
derive their fluid food already prepared from the contents of another
animal's intestines. In these cases the gut may altogether atrophy; as
in the _acanthocephala_ among the vermalia, the _entoconcha_ among the
mollusks, and the _sacculina_ among the crustacea.

The greater the extent of the body, and the more complex the
organization of the higher animals, the more necessary it is to have
an orderly and regular distribution of the nutritive fluid to all
parts. In the cœlenteria this work is accomplished by the gastric
canals (side branches from the gut, opening into its cavity) but in
the cœlomaria it is done much better by means of blood-vessels
(_vasa sanguifera_). These canals do not communicate directly with the
gastro-canal, but are formed independently of it in the surrounding
parenchyma of the mesoderm. They take up the filtered and chemically
improved food-fluid, which transudes through the intestinal walls, and
conduct it in the form of blood to all parts of the body. This blood
generally contains millions of cells, which are of great importance
in metabolism. The blood-cells of the lower cœlomaria are usually
colorless (leucocytes), while those of the vertebrates are mostly red
(rhodocytes).

The circulation of the blood in most of the cœlomaria is effected
by a heart, a contractile tube, formed by the local thickening of
a skin-vessel, which contracts and beats regularly by means of its
muscular bands. Originally two of these skin-vessels were developed in
the abdominal wall--a dorsal vessel in the upper and ventral vessel
in the lower wall (as in many of the vermalia). The heart is formed
from the dorsal vessel in the mollusks and articulates, but from the
ventral in the tunicates and vertebrates. The arteries are the vessels
which conduct the blood from the heart; those which conduct it from the
body to the heart are the veins. The finest branchlets of both kinds
of vessels, which form the connecting link between them, are called
capillaries; these immediately effect the interchange of matter in the
tissues by osmosis. The blood-vessels co-operate very closely with the
respiratory organs.

The interchange of gases in the organism, which we call breathing or
respiration--the taking in of oxygen and giving out of carbonic-acid
gas--does not require special organs in the lower animals. In these
it is accomplished by epithelial cells, which clothe the surface of
the body--the ectoderm of the outer skin layer and the entoderm of
the inner gut-covering. As nearly all these cœlenteria live in the
water, or (as parasites) in some fluid that contains air, and as these
fluids are constantly pouring in and out of the body, the exchange of
gases is accomplished at the same time. But in the higher animals this
is rarely found, only in the small animals of simple construction (such
as the rotifers and other vermalia, and the smallest specimens of the
mollusca and articulata). The majority of these cœlomaria attain a
considerable size, and so require special organs; these afford a larger
surface for the exchange of gases in the limited space, and accomplish
a very peculiar chemical work as the localized organs of respiration.
They fall into two groups according to the nature of the environment;
gills for breathing in water and lungs for breathing on land. The
latter take the oxygen directly from the atmosphere, and the former
from the water, in which atmosphere air is contained in solution.

The instruments of water-respiration which we call gills (_branchiæ_)
are generally attenuated parts or processes of the outer skin or the
inner gastric skin; hence we distinguish the two chief forms, external
and internal gills. Both are richly provided with blood-vessels which
bring the blood from the body for the purpose of aëration. Cutaneous
or external gills are especially found in the vertebrates, in the form
of threads, combs, leaves, pencils, tufts of feathers, etc., which are
drawn out from the entoderm as local processes of the outer skin, and
afford a wide surface for the interchange of gases between the body
and the water. In the mollusca there are usually a pair of comb-shaped
gills near the heart; in the articulates there are several pairs,
repeated in the different segments of the body. Gastric or internal
gills are peculiar to the vertebrates and the next-related tunicates,
with a small group of the vermalia, the enteropneusta. In these the
fore-gut or head-gut is converted into a gill-organ, the wall of which
is pierced with gill-fissures; the water that has been taken in by the
mouth passes away through the outer openings of these fissures. In the
lower aquatic vertebrates (acrania, cyclostoma, and fishes) the gills
are the sole organs of breathing; in the higher animals, that live in
the air, they fall into disuse, and their place is taken by lungs.
Nevertheless, heredity is so tenacious that we find from three to five
pairs of rudimentary gill-clefts in the embryo right up to man, though
they have long since ceased to have any function. This is one of the
most interesting of the palingenetic facts that prove the descent of
the amniotes (including man) from the fishes.

The group of the aquatic echinoderms has some very peculiar features of
respiration. Their body possesses an extensive water-duct, which takes
in the sea-water and returns it by special openings (skin-pores or
madreporites). The many branches of these water-vessels or ambulacral
vessels fill with water, especially the tiny feelers or feet, which
extend from the skin in thousands; they serve at once for movement,
feeling, and breathing. But many of the echinoderms have also special
gills--the star-fish have small finger-shaped cutaneous gills on
the back, the sea-urchins special leaf-shaped ambulacral gills, the
sea-cucumbers internal gastric gills (tree-shaped branching internal
folds of the rectum).

The organs of air-breathing are called, in general, lungs (_pulmones_).
Like the organs of water-breathing, they are formed sometimes from
the external and sometimes from the internal covering of the body.
Cutaneous or external lungs are found in several groups of the
vertebrates. Among the mollusks the land-dwelling lung-snails have
acquired a lung-sac by change in the work of the gill cavity: among
the articulata the lung-spiders and scorpions have two or more
trachea-lungs; that is to say, cutaneous sacs, in which are enclosed
fanwise a number of trachea-leaves. In the other air-breathing
articulates (tracheata) we find, instead of these simple or branched,
and often bushlike, air-tubes (_tracheæ_), which spread through the
whole body and conduct the air direct to the tissues. They take the
air from without by special air-holes in the skin (_stigmata_ and
_spiracula_). The myriapods and insects generally have numbers of
air-holes; the spiders only one or two, more rarely four, pairs. When
these air-tube animals return to an aquatic life (as happens with the
larvæ of various groups of insects), the outer air-holes close up, and
new thread-shaped or leaf-shaped trachea-gills are formed, which take
the air from the surrounding water by osmosis. The oldest and lowest
tracheata are the primitive air-tube animals, or protracheata, and form
the link between the older annelids and the myriapods. They have a
number of clusters of short air-tubes distributed over the whole skin,
and it is clear that these have been evolved from simple skin-glands by
change of function.

Gastric or internal lungs are only found in the higher animals, to
which we give the name of quadrupeds (or _tetrapoda_), the amphibia and
amniotes, and their fishlike ancestors, the dipneusta. These internal
lungs are sac-shaped folds of the fore-gut, formed originally from the
swimming-bladder (_nectocystis_) of the fishes by change of function.
This air-filled bladder, a sac-shaped appendage of the gullet, merely
serves the purpose of a hydrostatic organ, by varying the specific
weight, in the fishes. When the fish wishes to descend it contracts
the bladder and becomes heavier; it rises to the top by inflating it
again. The lungs were formed by the adaptation of the blood-vessels
in the wall of the swimming-bladder to the interchange of gases. In
the oldest living lung-fishes (_ceratodus_) it is still a simple sac
(_monopneumones_=one-lunged); in the others the simple gullet-cavity
divides early into a pair of sacs (_dipneumones_, two-lunged). The
wind-pipe (_trachea_--not to be confused with the organ of the same
name in the tracheata) is formed by the lengthening of their stalk
and strengthening of it with cartilaginous rings. At the anterior end
of the trachea we find already formed in the amphibia the larynx, the
important organ of voice and speech.

The function of removing unusable matter is not less important to the
organism than breathing. Just as breathing gets rid of the poisonous
carbonic acid, so the kidneys remove fluid and solid excreta in the
shape of urine; these are partly acid (uric acid, hippuric acid, etc.),
partly alkaline (urea, guanine, etc.). In most of the cœlomaria
special organs for removing these would be superfluous, as this is
accomplished (like breathing) by the stream of water that is constantly
passing through the whole body. But with the platodes we begin to
find important excretory organs in the nephridia, a pair of simple
and ramified canals which lie on either side of the gut, and open
outward. These primitive renal canals are transmitted by the platodes
to the vermalia, and by these to the higher stems of the cœlomaria.
In the latter they generally open by special funnels into the inner
body-cavity, which serves as first receptacle for the urine. Their
outer opening sometimes (primarily) goes through the outer skin at the
back (excretory pores), sometimes (secondarily) to the rectum, and
so out through the anus. The oldest articulates, the annelids, have
a pair of nephridia in each segment of the body; each renal canal,
or segmental canal, consists of three sections, an inner funnel
which opens into the body-cavity, a middle glandular section, and an
external bladder that ejects the urine by contraction. The disposition
of the renal system in the internally articulated vertebrates is very
similar to this; but now complicated structures begin to appear, a
pair of compact kidneys (_renes_), which are made up of a number of
branching nephridia. Three generations of kidneys succeed each other,
as phylogenetic stages of evolution--first the primary fore-kidneys
(_protonephros_), in the middle the secondary primitive kidneys
(_mesonephros_), and last the tertiary after-kidneys (_metanephros_).
The latter are only reached in the three highest classes of
vertebrates, reptiles, birds, and mammals. Mollusks also have a couple
of compact kidneys. They are developed from a pair of nephridia, the
funnels of which open internally into the heart-pouch (the remainder of
the reduced body-cavity); at the back they open outward. The crustacea
also have generally a pair of renal canals. On the other hand, the
protracheata (the stem-forms of the air-tube animals) have segmental
nephridia, a pair to each joint inherited from their annelid ancestors.
The rest of the tracheata, the myriapods, spiders, and insects, have,
instead of these, Malpighi tubes, funnel-shaped glands that arise from
the entodermal rectum, sometimes one pair or less, sometimes a number
in a cluster.

While most plants are purely plasmodomous, and most animals
plasmophagous, there are nevertheless in both organic kingdoms a
number of species (especially the lower) whose metabolism has assumed
peculiar forms by their relations to other organisms. To this class
belong especially the saprosites and parasites. By saprosites are
understood those plants and animals which feed entirely or mostly
on the corpses of other animals, or the decomposed matter which is
unfit for the food of higher animals. Among the unicellular protists
many of the bacteria, especially, belong to this class, and also many
fungilla (_phycomycetes_); among the metaphyta the fungi (mycetes),
and among the metazoa the sponges. I have already spoken of the many
peculiarities of metabolism in the ubiquitous bacteria; while many of
them cause putrefaction, they at the same time feed on the parts of
other organisms which have died. The fungi feed for the most part on
the decayed remains of plants and the products of putrefaction which
accumulate on the ground. In this character of scavengers they play the
same important part on land as the sponges do at the bottom of the sea.
But a number of small groups of the higher plants and animals have, as
a secondary habit, turned to saprositism. Among the metaphyta we have
especially the monotropea (to which our native asparagus, _monotropa
hypopitys_, belongs) and many orchids (_neottia_, _corallorhiza_). As
they find their plasm directly in the decayed matter in the woods,
they have lost their chlorophyll and green leaves. Among the metazoa
many of the vermalia, and some of the higher animals, such as the
rain-worm and many tube-dwelling annelids (the mud-eaters, _limicolæ_),
etc., live on putrid matter. The organs which their nearest relatives
use for obtaining, breaking up, and digesting food (eyes, jaws,
teeth, digestive glands) have been entirely or mostly lost by these
saprosites. Many of them form a transitional type to the parasites.

By parasites, in the narrower sense, we understand, in modern biology,
only those organisms which live on others and derive their nourishment
from them. They are numerous in all the chief divisions of the plant
and animal kingdoms, and their modifications are of great interest
in connection with evolution. No other circumstance has so profound
an influence on the organism as adaptation to a parasitic existence.
Moreover, there is no other section in which we can follow, step
by step, the course of the degeneration which is caused, and show
clearly the mechanical nature of the process. Hence the science of
parasites--parasitology--is one of the soundest supports of the theory
of descent, and provides an abundance of the most striking proofs of
the much-contested inheritance of acquired characteristics.

Among the unicellular organisms, the bacteria are the most conspicuous
instances of manifold adaptation to parasitic habits. As we count
these unnucleated protozoa among the oldest and simplest organisms,
and trace them directly by metasitism to the plasmodomous chromacea,
it is very probable that they turned to parasitism very early in the
history of life. Even a part of the monera (in which group we must
place the bacteria on account of their lack of a nucleus) found it
convenient and advantageous to prey on other protists and assimilate
their plasm directly, instead of going through the laborious process
of carbon assimilation themselves in the hereditary fashion. This is
also true of the large class of the sporozoa or fungilla (_gregarinæ_,
_coccidia_, etc.), real nucleated cells, which have adapted themselves
in various ways to parasitic habits. Many of them live in the
rectum, the cœlum, or other organs of the higher animals (the
gregarinæ, especially in the articulates); others in the tissues (for
instance, the sarcosporidia in the muscles of mammals, the coccidia
and myxosporidia in the liver of vertebrates). A good many of them
are "cell-parasites," and live inside the cells of other animals,
which they destroy; such are the hœmosporidia, which destroy the
blood-cells in man, and so cause intermittent fever.

Among the multicellular metaphyta it is particularly the fungi that
have taken to parasitism in various ways. Many of them are, as is
known, the most dangerous enemies of the higher animals and plants. The
various species of fungi cause certain diseases by their poisonous
(chemical) action on the tissues of their host. It is well known how
our most important cultivated plants, the vine, potato, corn, coffee,
etc., are threatened by fungoid diseases; and this is also true of many
of the lower and higher animals. It is probable that the fungi have
been evolved polyphyletically by metasitism from the algæ.

Among the higher metaphyta we find parasitism in many different
families, especially orchids, rhinanthacea (_orobranche_,
_lathraca_), convolvulacea (_cuscuta_), aristolochiacea, loranthacea
(_viscum_, _loranthus_), rafflesiacea, etc. These various kinds of
flowering-plants often grow to resemble each other by convergence
(that is to say, by their common adaptation to parasitic life); they
lose their green leaves, the plasmodomous chlorophyll of which is of
no further use to them. Frequently rudimentary leaves are left on them
in the form of colorless scales. For the purpose of clinging to the
plants they live on, and penetrating into their tissues, they evolve
special clinging apparatus (haustoria, suctorial cups, creepers). Their
stalks and roots are also modified in a characteristic way. The whole
productive force of these parasites is expended on their sexual organs;
_rafflesia_ has the largest flowers there are, more than a yard in
diameter.

Parasitism in the metazoa (in all groups) is even more frequent and
interesting than in the metaphyta. The mollusks and echinoderms
show the least disposition for it, and the platodes, vermalia, and
articulates the most. Even among the gastræada, the common ancestral
group of the metaphyta, we find parasites (kyemaria and gastremaria).
The protection they find inside their hosts is probably the reason
why these oldest of the metazoa have remained unchanged to the
present day. Real parasites are not numerous among the sponges and
cnidaria. But they are very numerous among the platodes. The suctorial
worms (_trematodes_) live partly externally (as ectoparasites)
on other animals and partly inside them (as endoparasites), and
produce serious diseases in them. They have lost the vibratory
coat of their free-living ancestors, the turbellaria, and acquired
clinging apparatus instead. The tape-worms (_cestodes_), which live
entirely in the interior of other animals, and are descended from the
suctorial worms, have lost their gastro-canal; they are nourished by
imbibition through the skin. The same degeneration is found in the
itchworms (_acanthocephala_) among the vermalia, the parasitic snails
(_entoconcha_) among the mollusks, and the root-crabs (_rhizocephala_)
among the crustacea.

The class of crustacea affords the most numerous and most instructive
examples of degeneration through parasitism, because in this class it
is found polyphyletically in very different orders and families, and
because their highly organized body shows every stage of degeneration
together in the different organs. The free-living crustacea generally
move about very rapidly and ingeniously; their numerous bones are
well jointed and excellently adapted for the most varied methods of
locomotion (running, swimming, climbing, digging, etc.); their organs
of sense are highly developed. As these are no longer used when
they take to parasitism, they atrophy and gradually disappear. The
younger crustacea all proceed from the same characteristic form of
the _nauplius_, and swim freely about; later, when they settle down
to parasitic habits, their organs of sense and locomotion atrophy. As
Fritz Müller-Desterro showed in his famous little work, _For Darwin_
(1864), forty years ago, the crustacea afford most luminous proofs of
the theory of descent and selection, and of progressive heredity and
the biogenetic law. These facts are the more important as the crab
undergoes the same degeneration by parasitic habits in a number of
different orders and families.

From parasitism we must entirely distinguish that intimate life-union
of two different organisms which we called symbiosis or mutualism.
Here we have an association of two living things for their mutual
benefit, while the parasite lives entirely at the expense of his
host. Symbiosis is found among the protista, being very wide-spread
among the radiolaria. In the gelatinous envelope (_calymma_) which
encloses the central capsule of their unicellular bodies we find a
number of motionless yellow cells (_zooxanthella_) scattered. These
are protophyta or (as it is said) "unicellular algæ" of the class of
paulotomea (_palmellacea_). They receive protection and a home from the
radiolaria, grow plasmodomously, and multiply by rapid segmentation.
A large part of the starch-flour and the plasm which they form by
carbon-assimilation goes as food directly to the radiolarium-host; the
other part of the xanthella goes on growing and multiplying. Similar
yellow zooxanthella or green zoochlorella are found as symbionta in the
tissues of many animals. Our common fresh-water polyp (_hydra viridis_)
owes its green color to the zoochlorella which live in great numbers
on the ciliated cells of its entoderm (the digestive gut-epithelium).
In general, however symbiosis is rarer in the metazoa than in the
metaphyta. In the latter case it is the fundamental feature of a whole
class of plants, the lichens. Each lichen consists of a plasmodomous
plant (sometimes a protophyte, sometimes an alga) and a plasmophagous
fungus. The latter affords a home, protection, and water to the green
alga, which repays the service by providing food.




XI

REPRODUCTION


 Reproduction and generation--Sexual
 and asexual reproduction--Superfluous
 growth--Monogony--Self-cleavage--Budding--Formation of
 spores--Amphigony--Ovum and sperm-cell--Hermaphrodite formation
 and separation of the sexes--Hermaphrodism and gonochorism
 of the cells--Monoclinism and diclinism--Monœcism and
 diœcism--Alternation of sex-division--Sexual glands of
 the histona--Hermaphroditic glands--Sexual ducts--Generative
 organs--Parthenogenesis--Pædogenesis--Metagenesis--Heterogenesis--
 Strophogenesis--Hypogenesis--Hybridism--Generation of hybrids and
 the species--Graduation of forms of reproduction.


While nutrition secures the maintenance of the organic individual,
reproduction insures that of the organic species, or the group of
definite forms which we distinguish from others by the name "species."
All individuals are more or less restricted in the duration of their
lives, and die off after the lapse of a certain time. The succession
of individuals, connected by reproduction and belonging to a species,
makes it possible for the specific form itself to last for ages. In
the end, however, the species is temporary; it has no "eternal life."
After existing for a certain period, it either dies or is converted by
modification into other forms.

The rise of new individuals by reproduction from parent organisms
is a natural phenomenon with definite time-restriction. It cannot
have continued from eternity on our planet, as the earth itself is
not eternal, and even long after its formation was incapable of
supporting organic life on its surface. This only became possible when
the surface of the glowing planet had sufficiently cooled for liquid
water to settle on it. Until this stage carbon could not enter into
those combinations with other elements (oxygen, hydrogen, nitrogen, and
sulphur) which led to the formation of plasm. As I intend to deal with
this process of _archigony_, or spontaneous generation, in a special
chapter, I leave it for the present, and confine myself to the study of
_tocogony_, or parental generation.

       *       *       *       *       *

The various forms of tocogony, or the reproduction of living things,
are generally divided into two large groups; on the one hand there is
the simple form of asexual generation (monogony), and on the other the
complex form of sexual generation (amphigony). In asexual generation
the action of one individual only is needed, this providing a product
of transgressive (redundant) growth which develops into a new organism.
In sexual generation it is necessary for two different individuals to
unite in order to produce a new being from themselves. This amphigony
(or _generatio digenea_) is the sole form of reproduction in man and
most of the higher animals. But in many of the lower animals and most
of the plants we find also asexual multiplication, or monogony, by
cleavage or budding. In the lowest organisms, the monera and many of
the protists, fungi, etc., the latter is the only form of propagation.

Strictly speaking, monogony is a universal life-process; even the
ordinary cell-cleavage, on which depends the growth of the histona, is
a cellular monogony. Hence historical biology must say that monogony
is the older and more primitive form of parental generation, and
that amphigony was secondarily developed from it. It is important to
emphasize this because, not only some of the older writers, but even
some recent ones, regard sexual generation as a universal function of
organisms, and declare that it dates from the very beginning of organic
life.

The complex and frequently very intricate phenomena of sexual
generation, as we find them in the higher organisms, become
intelligible to us when we compare them with the simpler forms of
asexual generation at the lowest stages of life. We then learn that
they are by no means unintelligible and supernatural marvels, but
natural physiological processes, which, like all others, may be traced
to the action of simple physical forces. The form of energy which
lies at the root of all tocogony is _growth_ (_crescentia_). And as
this phenomenon is also the cause, in the form of gravitation, of the
formation of crystals and other inorganic individuals, we do away with
another of the boundaries which people would establish between organic
and inorganic nature. Reproduction is a kind of nutrition and growth of
the organism beyond the individual standard, building up a part of it
into a whole. This _limit_ of individual size is determined for each
species by two factors--the inner constitution of the plasm, which is
inherited, and the dependence on the outer environment, which controls
adaptation. When this limit has been passed, the transgressive growth
takes the form of reproduction. Every species of crystal has also a
definite limit of growth; when this is passed, new crystal-individuals
are formed in the mother-water on the old individual, which grows no
further.

Asexual or monogenetic tocogony (also called "vegetative
multiplication") is always effected by a single organic individual,
and so must be traced to its transgressive growth. When this affects
the entire body as a total growth, the whole dividing into two or
more equal parts, we call the monogenetic process division (or
segmentation). But when the growth is partial, and affects only a
part of the individual, or when this special part separates from
the generating organism in the form of a bud (_gemma_), the process
is called budding or gemmation (_gemmatio_). Hence the essential
difference between the two forms of generation is that in division the
parent disappears in its partial products (children); these are of
the same age and form. But in budding the generating parent retains
its individuality; it is larger and older than the young bud. This
important difference between division and gemmation, which is often
overlooked, holds good both for protists (unicellulars) and histona
(multicellulars). The fact that in division the individual as such
is destroyed is a sufficient refutation of Weismann's theory of the
immortality of the unicellulars. (See above, and also the _Riddle_,
chapter xi.)

Reproduction by division is by far the most common of all forms of
propagation. It is the normal form of monogony, not only in many of the
protists, but also in the tissue-cells which compose the tissues of
the histona. It is, moreover, the sole method of propagation for most
of the monera, both chromacea and bacteria, which are in consequence
often comprised under the title of "cleavage-plants" (_schizophyta_).
Self-cleavage is also found among the higher multicellular
organisms--namely, the cnidaria (polyps, medusæ). It usually takes the
form of division into two parts (_dimidiatio_ or hemitomy), the body
splitting into two equal halves. The plane of division is sometimes
indefinite (fragmentary-cleavage), sometimes coincident with the long
axis (length-cleavage), sometimes with the transverse axis, vertical
to the long axis (transverse-cleavage), and less frequently with a
diagonal axis (oblique-cleavage). When the segmentation of a cell
proceeds so rapidly that the transverse-cleavage follows immediately
on the length-cleavage, and the two are at length made to coincide,
twofold division is changed into fourfold division. And when the
process is repeated in quick succession, and the body falls at last
into a number of small and equal pieces, we have manifold division
(polytomy); as in the spore-formation of the sporozoa and rhizopoda,
and in the embryonic sac of the phanerogams.

Asexual propagation by budding is chiefly distinguished from
segmentation by the fact that the determining transgressive growth is
only partial in the one and total in the other. The bud produced is,
therefore, younger and smaller than the parent from which it issues;
the latter may replace the lost part by regeneration and produce a
number of buds simultaneously or successively without losing its
individuality (whereas this is destroyed in division). Propagation
by budding is rare among the protists, and more common among the
histona--that is, with most of the tissue-plants and the lower,
stock-forming, tissue-animals (cœlenteria and vermalia). Most stocks
(cormi) are formed by a sprout or person shooting out buds which remain
united to it. The layer and shoots of tissue-plants are detached
buds. The two chief kinds of gemmation are terminal and lateral.
Terminal budding takes place at the end of the long axis, and is not
far removed from transverse division (for instance, the strobilation
of the acraspedæ medusæ and the chain tape-worms). Lateral budding is
much more common; it determines the branching of trees and generally of
complex plants, and also of the tree-shaped stocks of sponges, cnidaria
(polyps, corals), bryozoa, etc.

A third form of asexual reproduction is the formation of spores or
"germ-cells," which are usually produced in great numbers inside the
organism, then detached from it, and developed into new organisms
without needing fertilization. The spores are sometimes motionless
(rest-spores or paulospores); sometimes they have one or more lashes
which enable them to swim about (rambling-spores or planospores).
This monogenetic propagation is very common among the protists, both
protophyta and protozoa. Among the latter the sporozoa (gregarinæ,
coccidia, etc.) are remarkable for the passing away of the whole
unicellular organism in the formation of spores; in this case and
in many of the rhizopods (_mycetozoa_) the process coincides with
manifold cell-division. In other cases (radiolaria, thalamophora)
only a portion of the parental cells is used for the production of
spores. Spore-formation is very common among the cryptogams; here it
usually alternates with sexual propagation. The spores are generally
formed in special spore-capsules (sporangia). In the flowering plants
(anthophyta) sporogony has disappeared. It is found at times in the
tissue-animals (in the fresh-water sponges); in this case the sporangia
are called _gemmulæ_.

The essential feature of sexual generation is the coalescence of two
different cells, a female ovum (egg-cell) and a male sperm-cell.
The simple new cell which arises from the blending of these is the
stem-cell (_cytula_), the stem-mother of all the cells that make up
the tissues of the histon. But even among the unicellular protists
we find in many places the beginnings of sexual differentiation; it
is foreshadowed in the blending or copulation of two homogeneous
cells, the gameta. We may conceive this process, or zygosis, as a
peculiar and very favorable kind of growth, that is connected with a
rejuvenescence of the plasm; the latter is enabled to propagate by
repeated cleavage through the mixing of the two different plasma-bodies
on either side (_amphimixis_). When these two gameta become unequal
and differ in size and shape, the larger female body is called the
macrogameton or macrogonidion, and the smaller, male part, the
microgameton or microgonidion. Among the histona the first is called
the egg-cell (_ovulum_), and the latter the sperm-cell (_spermium_, or
_spermatozoon_). As a rule the latter is a very mobile ciliated cell,
the former an inert or amœboid cell. The vibratory movements of the
sperm-cells serve for approaching the ovulum in order to fertilize it.

The qualitative difference between the two copulating sexual cells
(_gonocyta_), or the chemical difference between the ovoplasm of the
female and the sperm-plasm of the male cell, is the first (and often
the only) condition of amphigony; subsequently we find in addition (in
the higher histona) a very elaborate apparatus of secondary structures.
With this chemical difference is associated a peculiar double form of
sensitive perception and an attraction based thereon, which is called
sexual chemotaxis or erotic chemotropism. This "sex-sense" of the two
gonocyta, or elective affinity of the male androplasm and the female
gynoplasm, is the cause of mutual attraction and union. It is very
probable that this sexual sense-function, akin to smell or taste, and
the movements it stimulates, are located in the cytoplasm of the two
sex-cells, while heredity is the function of the caryoplasm of the
nucleus. (_Cf._ the _Anthropogeny_, chapters vi. and vii.)

The sexual difference between the two forms of gonoplasm, the ovoplasm
of the female and spermoplasm of the male cell, is noticeable at the
very beginning of sexual differentiation in the different sizes of
the copulating gameta, and later in their increasing divergence as to
shape, composition, movement, etc. It leads further to the distribution
of the germinal regions (in which the sex-cells are formed) into two
different individuals. When the ovum and the sperm-cell are produced in
one and the same individual, we call this an hermaphrodite; and when
they are formed in two different individuals (male and female), we
call them monosexual, or gonochorists. In accordance with the various
stages of individuality which we distinguished above (chapter vii.), we
may indicate the following stages of hermaphrodism and gonochorism.

Some groups of protists, especially the highly organized ciliated
infusoria (_ciliata_), are distinguished by having a separation of
male and female plasm within the unicellular organism. The ciliata
propagate, as a rule, in large numbers by repeated division (by
indirect cell-cleavage). But this monogony has its limits, and has to
be interrupted from time to time by amphigony, a rejuvenation of the
plasm, which is effected by the conjugation of two different cells and
the partial destruction of their nuclear matter. By conjugation is
meant the partial and momentary union of two different unicellulars,
while copulation is a total and permanent coalescence. When two
ciliated infusoria conjugate they place themselves side by side, and
connect for a time by means of a bridge of plasm. A part of the nucleus
of each has already divided into two portions, one of which functions
as the female standing-nucleus (_paulocaryon_) and the other as the
male travelling-nucleus (_planocaryon_). The two mobile nuclei enter
the plasm-bridge, and move through it, pushing against each other,
into the body of the opposite cell; they then coalesce with the deeper
lying standing-nucleus. When a fresh nucleus has been thus formed (by
_amphimixis_) in each of the copulating cells, they again separate. The
two rejuvenated cells have once more acquired the power to propagate
for a long time by division.

This peculiar hermaphroditic formation of the cells, which
distinguishes the ciliated infusoria and some other protists, and
which we now know in its smallest details through the investigations
of Richard Hertwig, Maupas, and others, is especially interesting
because it proves that the chemical difference between the female
gynoplasm and the male androplasm can be found within a single cell.
This erotic division of labor is so important that formerly it was
universally ascribed to two different cells. Recent accurate research,
penetrating into the smallest visible processes of fertilization, has
shown that the essential feature in the formation of a fresh individual
(the stem-cell) is the blending of equal portions (hereditary parts)
of the male and female nuclei; the caryoplasm of the two copulating
cells is the vehicle of heredity from the parents. The cytoplasm of the
cell-body, on the other hand, serves the purposes of adaptation and
nutrition. As a rule the cell-body of the ovulum is very large, and
is, as a food-store, very richly provided with albumin, fat, and other
nutritive matter (food-yolk); while the cytoplasm of the sperm-cell is
very small, and generally forms a vibrating lash, with which it moves
along and seeks the ovum.

In most of the plants the female and male cells are produced by the
same sprout, and in many of the lower animals by one and the same
person. This kind of hermaphrodism in "individuals of the second order"
is called monoclinism ("one-beddedness"). In many of the higher plants
(monœcic stocks) and most of the higher animals we have diclinism
("two-beddedness")--in other words, the one sprout or person has
only male, and the other sprout or person only female, organs--this
is gonochorism of individuals of the second order. Monoclinism is
generally associated with sedentary life (and often necessary for it),
and diclinism with free movement. Adaptation to parasitic habits also
favors monoclinism; thus, the crabs, for instance, are for the most
part gonochoristic individuals, but the creeping crabs (_cirripedia_),
which have adopted sedentary (and to an extent parasitic) habits, have
become hermaphrodites in consequence. Many intestinal parasites among
the lower animals (such as tape-worms, suctorial worms, wonder-snails),
which live isolated lives inside other animals, have to be
hermaphroditic and able to fertilise themselves if the species is to be
maintained. On the other hand, many hermaphroditic flowers, although
they have both sorts of sex-organs, are incapable of fertilizing
themselves and have to receive this from insect visitors which carry
the pollen from one flower to another.

Individuals of the third order, which we call stocks (_cormi_) in both
the plant and animal worlds, also exhibit varying features in the
sex-persons which compose them. When male and female diclinic sprouts
or persons are found side by side on the same stock, we call this
hermaphrodism of the cormi _monœcia_ ("one-housedness"); this is the
case with most of the siphonophora and some of the corals. _Diœcia_
("two-housedness") is less common: in this one stock has only male and
the other only female sprouts or persons, as in poplars and osiers,
most of the corals, and some of the siphonophora. The physiological
advantages of crossing--the union of sex-cells of different
individuals--favor progressive sex-division in the higher organisms.

A comparative study of the features of hermaphrodism and sex-division
in the plant and animal worlds teaches us that both forms of
sex-activity are often found in closely related organisms of one and
the same group, sometimes even in different individuals of the same
species. Thus, for instance, the oyster is usually gonochoristic, but
sometimes hermaphroditic; and so with many other mollusks, vermalia,
and articulata. Hence, the question often raised, which of the two
forms of sex-division is original, is hardly susceptible of a general
answer, or without relation to the stage of individuality and the place
in classification of the group under discussion. It is certain that in
many cases hermaphrodism represents the original feature; for instance,
in most of the lower plants and many of the stationary animals
(sponges, polyps, platodes, tunicates, etc.). Where we find exceptions
in these groups, they are of secondary origin. It is equally certain,
on the other hand, that in other cases the separation of the sexes is
the primitive arrangement; as in siphonophoræ, ctenophoræ, bryozoa,
cirripedia, and mollusks. In these cases the hermaphrodism is clearly
secondary in the sense that the hermaphrodites descend originally from
gonochorists.

It is only in a few sections of the lowest histona that the two kinds
of sex-cells arise without a definite location in different parts of
the simple tissue, as in a few groups of the lower algæ and in the
sponges. As a rule they are formed only at definite positions and in a
special layer of the tissue-body, and mostly in groups, in the shape
of sexual glands (_gonades_). These bear special names in different
groups of the histona. The female glands are called archegonia in
the cryptogams, _nucellus_ (formed from the macrosporangia of the
pteridophyta) in the phanerogams, and ovaries in the metazoa. The male
glands are called antheridia in the cryptogams, pollen-sacs (formed
from the microsporangia of the ferns) in the phanerogams, and testicles
(_as spermaria_) in the metazoa. In many cases, especially in aquatic
lower animals, the ovula (as products of the ovaries) are discharged
directly outward. But, in most of the higher organisms, special sexual
ducts (_gonoductus_) have been formed to conduct both kinds of the
gonocyta out of the organism.

While the two kinds of sexual glands are usually located in different
parts of the generating organism, there are, nevertheless, a few cases
in which the sex-cells are formed directly and together from one and
the same gland. These glands are called hermaphroditic glands. Such
structures are very notable in several highly differentiated groups
of the metazoa, and have clearly been developed from gonochoristic
structures in lower forms. The class of crested medusæ, or ribbed
medusæ (ctenophoræ), contains glasslike, sea-dwelling cnidaria of a
peculiar and complicated build, which probably descend from hydromedusæ
(or craspedota). But whereas the latter have very simple gonochoristic
structures (four or eight monosexual glands in the course of the
radial canals or in the gastric wall), in the ctenophoræ the eight
hermaphroditic canals run in a meridian arch from one pole of the
cucumber-shaped body to the other. Each canal corresponds to a ciliary
streamer, and forms ovaries at one border and testicles at the other;
and these are so arranged that the eight intercostal fields (the spaces
between the eight streamers) are alternately male and female. Still
more curious are the hermaphroditic glands of the highly organized,
land-dwelling, and air-breathing lung-snails (_pulmonata_), to which
our common garden snail (_arion_) and vineyard snail (_helix_) belong.
Here we have a hermaphroditic gland with a number of tubes, each of
which forms ovaries in its outer part and sperma in the inner. Still
the two kinds of sex-cells lead separately outward.

In most of the lower and aquatic histona both kinds of sex-cells,
when they are ripe, fall directly into the water, and come together
there. But in most of the higher, and especially the terrestrial,
organisms special exits or conducting canals have been formed for the
sex-products, the sexual ducts (_gonoductus_); in the metazoa the
female have the general name of oviducts and the male spermaducts (or
_vasa deferentia_). In the viviparous histona special canals serve
for the conveyance of the sperm to the ovum, which remains inside the
mother's body; such are the neck of the archegonium in the cryptogams,
the pistil in the phanerogams, and the vagina in the metazoa. At the
outer opening of these conducting canals special copulative organs are
developed, as a rule.

When the ejected sex-cells do not directly encounter each other (as in
many aquatic organisms), special structures have to be formed to convey
the fertilizing sperm from the male to the female body. This process of
copulation becomes important, as it is associated with characteristic
feelings of pleasure, which may cause extreme psychic excitement; as
sexual love it becomes, in man and the higher animals, one of the most
powerful springs of vital activity. In many of the higher animals
(namely, vertebrates, articulates, and mollusks) there are also formed
a number of glands and other auxiliary organs which co-operate in the
copulation.

The manifold and intimate relations which exist, in man and the higher
animals (especially vertebrates and articulates), between their sexual
life and their higher psychic activity, have given rise to plenty of
"wonders of life." Wilhelm Bölsche has so ably described them in his
famous and popular work, _The Life of Love in Nature_, that I need only
refer the reader to it. I will only mention the great significance of
what are called "secondary sexual characters." These characteristics
of one sex that are wanting in the other, and that are not directly
connected with the sexual organs--such as the man's beard, the woman's
breasts, the lion's mane, or the goat's horns--have also an æsthetic
interest; they have, as Darwin showed, been acquired by sexual
selection, as weapons of the male in the struggle for the female,
and vice versa. The feeling of beauty plays a great part in this,
especially in birds and insects; the beautiful colors and forms which
we admire in the male bird of paradise, the humming-bird, the pheasant,
the butterfly, etc., have been formed by sexual selection (_cf._ the
_History of Creation_).

In various groups of the histona the male sex has become superfluous
in the course of time; the ovula develop without the need of
fertilization. That is particularly the case in many of the platodes
(trematodes) and articulates (crustacea and insects). In the bees we
have the remarkable feature that it is only decided at the moment
of laying the egg whether it is to be fertilized or not; in the one
event a female and in the other a male bee is formed from it. When
Siebold proved at Munich these facts of miraculous conception in
various insects, he was visited by the Catholic archbishop of the
city, who expressed his gratification that there was now a scientific
explanation possible of the conception of the Virgin Mary. Siebold
had, unfortunately, to point out to him that the inference from the
parthenogenesis of the articulate to that of the vertebrate was not
valid, and that all mammals, like all other vertebrates, reproduce
exclusively from impregnated ova. We also find parthenogenesis
among the metaphyta, as in the _chara crinita_ among the algæ, the
_antennaria alpina_ and the _alchemilla vulgaris_ among the flowering
plants. We are, as yet, ignorant for the most part of the causes
of this lapse of fertilization. Some light has been thrown on it,
however, by recent chemical experiments (the effect of sugar and
other water-absorbing solutions), in which we have succeeded in
parthenogenetically developing unfertilized ova.

In the higher animals the complete maturity and development of
the specific form are requisite for reproduction, but in many of
the lower animals it has been observed recently that ovula and
sperm-cells are even formed by the younger specimens in the larva
stage. If impregnation takes place under these conditions, larvæ of
the same form are born. And when these larvæ have afterwards reached
maturity and reproduced in this form, we call the process _dissogony_
("double-generation"). It is found in many of the cnidaria, especially
the medusæ. But if larvæ propagate by unfertilized ova, and so
reproduce their kind parthenogenetically, the process is known as
_pædogenesis_ ("young-generation"). It is found particularly in the
platodes (trematodes) and some of the insects (larvæ of _cecidomyca_
and other flies).

In a large number of lower animals and plants sexual and asexual
generation regularly alternate. Among the protists we find this
alternation of generation in the sporozoa; among the metaphyta in the
mosses and ferns; and among the metazoa in the cnidaria, platodes,
tunicates, etc. Often the two generations differ considerably in shape
and degree of organization. Thus, in the mosses the asexual generation
is the spore-forming moss capsule (_sporogonium_), while the sexual is
the moss plant with stalk and leaves (_culmus_). In the case of the
ferns, on the other hand, the latter is spore-forming and monogenetic,
while the thallus-formed, simple, and small fore-germ (_prothallium_)
is sexually differentiated. In most of the cnidaria a small stationary
polyp is developed out of the ovum of the free-swimming medusa, and
this polyp, in turn, generates by budding medusæ, which reach sexual
maturity. In the tunicates (salpa) a sexual social form alternates with
an asexual solitary form; the chain-salpa of the former are smaller and
differently shaped than the large individual salpa of the latter, which
again generate chains by budding. This special form of metagenesis was
the first to be observed, as it was in 1819 by the poet Chamisso, when
he sailed round the world. In other cases (for instance, in the closely
related _doliolum_) a sexual generation alternates with two (or more)
neutral ones. The explanation of these various forms of alternating
generations is given in the laws of latent heredity (atavism), division
of labor, and metamorphosis, and especially by the biogenetic law.

While in real metagenesis (alternation of generations in the strict
sense) the asexual generation propagates by budding or spore-formation,
this is done parthenogenetically in the cognate process of
heterogenesis. This it is which, especially in many of the articulates,
causes an immense increase of the species in a short time. Among the
insects we have the leaf-lice (aphides), and among the crustacea the
water-fleas (daphnides), that propagate in great numbers during warm
weather by unfertilized "summer-ova." It is not until the autumn that
males appear and fertilize the large "winter-ova"; in the following
spring the first parthenogenetic generation issues from the winter
eggs. The two heterogenetic generations are very different in the
parasitic suctorial worms (trematodes). From the fertilized ovum of the
hermaphrodite distoma we get simply constructed nurses (pædogenetic
larvæ), inside which cercaria are generated from unfertilized ova;
these travel, and are afterwards converted (inside another animal) into
distoma once more.

I have given (_General Morphology_, chap, ii., p. 104) the name of
strophogenesis to the complicated process of cell-reproduction,
which we find in the ontogeny of most of the higher histona, both
phanerogams and cœlomaria. In these there is not a real alternation
of generations, as the multicellular tissue-forming organism develops
directly from the impregnated ovum. But the process resembles
metagenesis in so far as the ontogenetic construction consists itself
in a repeated division of the cells. Many generations of cells proceed
by cleavage from the one stem-cell (the impregnated ovum) before two
of these cells become sexually differentiated, and form a generation
of sexual cells. However, the essential difference consists in the
fact that all these generations of cells--in the body of both the
higher animals and the flowering plants--remain joined together as
parts of a single bion (a unified physiological individual); but in
the alternation of generations each group produced is made up of a
number of bionta, which live as independent forms--often so different
from each other that they were formerly thought to be animals of
separate classes, such as the polyps and medusæ. Hence we must not
describe the reproductive circle of the phanerogams as an alternation
of generations, although it has started from the fern (by abbreviated
heredity).

All simple forms of sexual reproduction without alternation of
generations are comprised under the title of _hypogenesis_. The
generative cycle proceeds from ovum to ovum in one and the same
bion or physiological individual. This form of development is usual
with most of the higher animals and plants; it may proceed with or
without metamorphosis. The younger forms which arise temporarily in
the latter case, and are distinguished from the sexually ripe form
by the possession of the provisional (and subsequently disappearing)
organs--larva organs (for instance, the tadpole or the pupa), are
comprised under the general head of larvæ.

As a rule, only organisms of the same species seem to have sexual
union and generate fertile progeny. This was formerly a rigid dogma,
and served the purpose of defining the loose idea of the species.
It was said: "When two animals or plants can have fertile offspring
they belong to the same real species." This principle, which once
afforded support to the dogma of the constancy of species, has long
been discarded. We now know by numbers of sound experiments that not
only two closely related species, but even two species of different
genera, may have sexual intercourse in certain circumstances, and that
the hybrids thus generated can have fertile offspring, either by union
among themselves or with one of the parents. However, the disposition
to hybridism varies considerably, and depends on the unknown laws of
sexual affinity. This sexual affinity must be based on the chemical
properties of the plasm of the copulating cells, but it seems to show
a good deal of vagueness in its effect. As a rule, hybrids exhibit a
combination of the features of both parents.

It has been proved by many recent experiments that hybrids have a more
powerful build and can reproduce more strongly than pure offspring,
whereas pure selection has generally in time an injurious effect. A
freshening by the introduction of new blood seems to be good from time
to time. Hence, it is just the reverse of what the former dogma of the
constancy of species affirmed. The question of hybridism has, generally
speaking, no value in defining the species. Probably many so-called
"true species," which have relatively constant features, are really
only permanent hybrids. This applies especially to lower sea-dwelling
animals, the sexual products of which are poured into the water and
swarm together in millions. As we know of various species of fishes,
crabs, sea-urchins, and vermalia, that their hybrids are very easily
produced and maintained by artificial impregnation, there is nothing to
prevent us from believing that such hybrids are also maintained in the
natural state.

The short survey we have made of the manifold varieties of reproduction
is sufficient to give an idea of the extraordinary wealth of this world
of wonders. When we go more closely into details we find hundreds of
other remarkable variations of the process on which the maintenance
of the species depends. But the most important point of all is the
fact that all the different forms of tocogony may be regarded as
connected links of a chain. The steps of this long ladder extend
uninterruptedly from the simple cell-division of the protists to the
monogony of the histona, and from this to the complicated amphigony
of the higher organisms. In the simplest case, the cell-cleavage of
the monera, propagation (by simple transverse division) is clearly
nothing more than transgressive growth. But even the preliminary
stage of sexual differentiation, the copulation of two equal cells
(_gameta_), is really nothing but a special form of growth. Then, when
the two gameta become unequal in the division of labor, when the larger
inert macrogameton stores up food in itself, and the smaller, mobile
microgameton swims in search of it, we have already expressed the
difference between the female ovum and the male sperm-cell. And in this
we have the most essential feature of sexual reproduction.

The reproduction of the organism is often regarded as a perfect mystery
of life, and as the vital function which most strikingly separates
the living from the lifeless. The error of this dualistic notion is
clear the moment one impartially considers the whole gradation of
forms of reproduction, from the simplest cell-division to the most
elaborate form of sexual generation, in phylogenetic connection. It is
obvious all through that transgressive growth is the starting-point
in the formation of new individuals. But the same must be said of
the multiplication of inorganic bodies--the cosmic bodies on the
larger scale, crystals on the smaller scale. When a rotating sun
passes a certain limit of growth by the constant accession of falling
meteorites, nebulous rings are detached at its equator by centrifugal
force, and form into new planets. Every inorganic crystal, too, has
a certain limit of individual growth (determined by its chemical and
molecular constitution). However much mother-water you add, this
is never passed, but new crystals (daughter-crystals) form on the
mother-crystal. In other words, growing crystals propagate.




XII

MOVEMENT

 Mechanics as the science of motion (kinematics and
 phoronomism)--Chemistry of vital movement--Active and passive
 movements--Undulatory movement--Mechanism of imbibition--Autonomous
 and reflex movements--Will and willing--Mixed movements--Movements
 of growth--Direction of the vital movement--Direction of the
 crystallizing force--Direction of cosmic motion--Movements of
 protists--Amœboid, myophenous, hydrostatic, secretory, vibratory
 movements: cilia and lashes--Movements of histona, metaphyta, and
 metazoa--Locomotion of tissue animals: ciliary motion and muscular
 movements--Muscles of the skin--Active and passive organs of
 movement--Radiata, articulata, vertebrata, mammalia--Human movements.


All things in the world are in perpetual motion. The universe is a
_perpetuum mobile_. There is no real rest anywhere; it is always
only apparent or relative. Heat itself, which constantly changes, is
merely motion. In the eternal play of cosmic bodies countless suns and
planets rush hither and thither in infinite space. In every chemical
composition and decomposition the atoms, or smallest particles of
matter, are in motion, and so are the molecules they compose. The
incessant metabolism of the living substance is associated with a
constant movement of its particles, with the building up and decay of
plasma-molecules. But here we must disregard all these elementary kinds
of movement, and be content with a brief consideration of those forms
of motion which are peculiar to organic life, and a comparison of them
with the corresponding motions of inorganic bodies.

The science of motion, or mechanics, is now taken in very different
senses: (1) in the widest sense as a philosophy of life [generally
called mechanism or mechanicism in England], equivalent to either
monism or materialism; (2) in the stricter sense as the physical
science of motion, or of the laws of equilibrium and movement in
the whole of nature (organic and inorganic); (3) in the narrowest
sense as part of physics, or dynamics, the science of moving forces
(in opposition to statics, the science of equilibrium); (4) in the
purely mathematical sense as a part of geometry, for the mathematical
definition of magnitudes of movement; and (5) in the biological sense
as phoronomy, the science of the movements of organisms in space.
However, these definitions are not yet universally adopted, and
there is a good deal of confusion. It would be best to follow the
lead of Johannes Müller, as we are going to do here, and restrict
the name phoronomy to the science of the vital movements which are
peculiar to organisms, in contrast to kinematics, the exact science
of the inorganic movements of all bodies. The real material object
of phoronomy is the plasm, the living matter that forms the material
substratum of all active vital movements.

On our monistic principles the inner nature of organic life consists in
a chemical process, and this is determined by continuous movements of
the plasma-molecules and their constituent atoms. As we have already
considered this metabolism in the tenth chapter, we need do no more
here than point out that both the general phenomena of molecular
plasma-movement and their special direction in the various species of
plants and animals can be reduced in principle to chemical laws, and
are subject to the same laws of mechanics as all chemical processes
in organic and inorganic bodies. In this we emphasize our opposition
to vitalism, which sees in the _direction_ of plasma-movement the
supernatural influence of a mystical vital force or of some ghostly
"dominant" (Reinke). We agree with Ostwald, who also reduces these
complex movements to the play of energy in the plasm--that is to say,
in the last instance to modifications of chemical energy. In regard to
the visible movements of the living things which concern us at present,
we must first distinguish passive and active, and subdivide the latter
into reflex and autonomous.

Many movements of the living organism which the inexpert are inclined
to attribute to life itself are purely passive; they are due either to
external causes which do not proceed from the living plasm, or to the
physical composition of the organic but no longer living substance.
Purely passive movements, which play an important part in bionomy and
chorology, comprise such as the flow of water and the rush of the wind;
they cause considerable changes of locality and "passive" migrations
of animals and plants. Purely physical, again, is what is known as the
Brownian molecular movement which we observe with a powerful microscope
in the plasm of both dead and living cells. When very fine granules
(for instance, of ground charcoal) are equally distributed in a liquid
of a certain consistency, they are found to be in a constant shaking or
dancing movement. This movement of the solid particles is passive, and
is due to the shocks of the invisible molecules of the fluid which are
continually impinging upon each other. In the rhizopods--the remarkable
protozoa whose unicellular organism sheds so much light on the obscure
wonders of life--we notice a curious streaming of the granules in
the living plasm. Within the cytoplasm of the amœbæ particles
travel up and down in all directions. On the long thin plasma-threads
or pseudopodia which stream out from the unicellular body of the
radiolaria and thalamophora, thousands of fine particles move about,
like promenaders in a street. This movement does not come from the
passive granules, but from the active invisible molecules of the
plasm, which are always changing their relative positions. Thus also
the movements of the blood-cells which we can see with the microscope
in the circulation of a young transparent fish, or in the tail of a
frog-larva, are not due to the action of the blood-cells themselves,
but to the flow of the blood caused by the beat of the heart.

An important factor in the life of many organisms, especially the
higher plants, is the physical phenomenon called _imbibition_; it
consists in the penetration of water between the molecules of solid
bodies (drawn to them by molecular attraction), and the consequent
displacement of the molecules by the fluid. In this way the volume of
the solid body is increased, and movements are produced which may have
the appearance of vital processes. The energy of these imbibitional
bodies is notoriously very powerful; we can, for instance, split large
blocks of stone by the insertion of a piece of wood dipped in water. As
the cellulose membrane of plant-cells has this property of imbibition
in a high degree (either in the living or the dead cell), the movements
it causes are of great physiological importance. This is especially
the case when the imbibition of the cell wall is one-sided, and causes
a bending of the cell. In consequence of the unequal strain in the
drying of many fruits, they split open and project their seeds to some
distance (as do the poppy, snap-dragon, etc.). The moss-capsules also
empty their spores as a result of imbibition-curving (in the teeth
of the openings of the spore-cases). The hygroscopic points of the
heron-bill (_erodium_) curl up in the dry state and stretch out when
moist; hence they are used as hygrometers in the construction of
meteorological huts. The so-called "resurrection plants" (_anastatica_,
the rose of Jericho, and _selaginella lepidophylla_), which close up
like a fist when dry, spread their leaves out flat when moistened (the
leaves imbibing strongly on the inner side). There is no more real
case of "resuscitation" (as many believe) in these cases than in the
mythological resurrection of the body. However, these phenomena of
imbibition are not active vital processes; they are independent of the
living plasm, and due solely to the physical constitution of the dead
cell-membranes.

In contrast with these passive movements of organisms, we have
the active movements which proceed from the living plasm. In the
ultimate analysis, it is true, these may be reduced to the action of
physical laws just as well as the passive movements. But the causes
of them are not so clear and obvious; they are connected with the
complicated chemical molecular processes of the living plasm, of the
physical regularity of which we are now fully convinced, though their
complicated mechanism is not yet understood. We may divide into two
groups the many different movements, which are called vital in this
stricter sense, and were formerly regarded as evidences of the presence
of a mystic vital force, according as the stimulus--the sensation of
which is caused by the movement--is directly perceptible or not. In
the first case, we have stimulated (or reflex or paratonic) movements,
and in the second voluntary (autonomous or spontaneous) movements. As
the will appears to be free in the latter, they have been left out of
consideration by many physiologists, and handed over to the treatment
of the metaphysical psychologist. On our monistic principles this is a
grave error; nor is it improved when "psychonomism" appeals to a false
theory of knowledge. On the contrary, the conscious will (and conscious
sensation) is itself a physical and chemical process like unconscious
and involuntary movement (and unconscious feeling). They are both
equally subject to the law of substance. However, only the external
stimuli which cause reflex movements are known to us to any great
extent and experimentally recognizable; the internal stimuli, which
affect the will, are mostly unknown, and are not directly accessible
to investigation. They are determined by the complicated structure of
the psychoplasm, which has been gradually acquired by phylogenetic
processes in the course of millions of years.

The great problem of the will and its freedom--the seventh and last
of Dubois-Reymond's world-riddles--has been dealt with fully in the
_Riddle_ (chapter vii.). But as we still meet with the most glaring
contradictions and confusion in regard to this difficult psychological
question, I must touch upon it briefly once more. In the first place, I
would remind the reader that it is best to restrict the name "will" to
the purposive and conscious movements in the central nervous system of
man and the higher animals, and to give the name of impulses (tropisms)
to the corresponding unconscious processes in the psychoplasm of the
lower animals, as well as of the plants and protists. For it is only
the complicated mechanism of the advanced brain structure in the higher
animals, in conjunction with the differentiated sense-organs on the one
side and the muscles on the other, that accomplishes the purposive and
deliberate actions which we are accustomed to call acts of will.

But the distinction between voluntary (autonomous) and involuntary
(reflex) movements is as difficult to carry out in practice as it is
clear in theory. We can easily see that the two forms of movement
pass into each other without any sharp boundary (like conscious and
unconscious sensation). The same action, which seems at first a
conscious act of the will (for instance, in walking, speaking, etc.),
may be repeated the next moment as an unconscious reflex action. Again,
there are many important mixed or instinctive movements, the impulse to
which comes partly from internal and partly from external stimuli. To
this class belong especially the movements of growth.

Every natural body that grows increases its extent, fills a larger
part of space, and so causes certain movements of its particles; this
is equally true of inorganic crystals and the living organism. But
there are important differences between the growth in the two cases.
In the first place, crystals grow by the external apposition of fresh
matter, while cells grow by the intussusception of fresh particles
within the plasm (_cf._ chapter x.). In the second case, in growth,
which determines the whole shape of the organism, two important factors
always co-operate, the inner stimulus, which depends on the specific
chemical constitution of the species, and is transmitted by heredity,
and the external stimulus which is due to the direct action of light,
heat, gravity, and other physical conditions of the environment, and is
determined by adaptation (phototaxis, thermotaxis, geotropism, etc.).

A peculiar property of many vital movements (but by no means all)
is the definite direction they exhibit; these are generally called
purposive movements. For the teleologist they afford one of the chief
and most welcome proofs of the dualistic theory of the older and the
modern vitalism. Baer, especially, has laid stress on the purposiveness
of all vital movement. It has been given a more precise expression
recently by Reinke. His "dominants" are "intelligent directive
forces," essentially different from all forms of energy or natural
forces, and not subject to the law of substance. These metaphysical
"vital spirits" are much the same as the immortal soul of dualistic
psychology or the divine emanations of ancient theosophy. They are
supposed not only to regulate the special development and construction
of every species of animal and plant, and direct it to a predetermined
end, but also to control all the various movements of the organism
and its organs down to the cells. These "hyperenergetic forces" are
equivalent to the "organizing principle" and the "unconscious will"
of Edward Hartmann, the "arranging and controlling protoplasmic
forces" of Hanstein and others. All these metaphysical, supernatural,
and teleological ideas, like the older mystic notion of a special
vital force, rest on a perversion of judgment by the apparent freedom
of will and purposiveness of organization in the higher organisms.
These thinkers overlook the fact that this purposiveness can be
traced phylogenetically to simple physical movements in the lower
organisms. Moreover, they overlook or deny the definite direction of
inorganic forms of energy, though this is just as clear in the origin
of a crystal as in the composition of the whole world-structure, in
the direction of the mind as in the orbit of a planet. Hence it is
important to bear in mind always these two forms of mechanical energy,
and emphasize their identity with the direction of vital movement.

The force of gravitation which is at work in crystal-formation in
the simple chemical body exhibits just as definite a direction as
that which appears in the plasm in cell-construction. In this and
other respects the comparison of the cell with the crystal, which was
made even by the founders of the cell-theory, Schleiden and Schwann,
in 1838, is thoroughly justified, though it is not correct in some
other aspects. When the crystal is formed in the mother-water, the
homogeneous particles of the chemical substance arrange themselves
in a perfectly definite direction and order, so that mathematical
planes of symmetry and axes arise within, and definite angles at the
surface. On the strength of this, modern crystallography distinguishes
six different systems of crystals. But, in different conditions, the
same substance may crystallize in two or even three different systems
(dimorphism and trimorphism of the crystal); thus, for instance,
carbonate of lime crystallizes as calcspar in the hexagonal, and as
arragonite in the rhombic system. If Reinke would be consistent, he
ought to postulate a "dominant" for every crystal, to control the order
and direction of the particles in its formation. He makes the curious
statement (in 1899) that direction "is not a measurable magnitude" like
energy, and so is not subject, like it, to the law of substance. We can
mathematically determine the direction of the constructive force in the
crystal just as well as in the cell.

If we comprise under the head of cosmokinesis the whole of the
movements of the heavenly bodies in space, we cannot deny that they
have a definite direction in detail, although our knowledge of this is
still very incomplete. We can calculate the distances and speeds and
movements of the planets round the sun with mathematical accuracy; and
we gather from our astronomical observations and calculations that a
similar regularity prevails in the movements of the other countless
bodies in infinite space. But we do not know either the first impulse
to these complex movements or their final goal. We can only conclude
from the great discoveries of modern physics, supported by spectrum
analysis and celestial photography, that the universal law of substance
on the one side and the law of evolution on the other control the
gigantic movements of the heavenly bodies just as they do the living
swarm of tiny organisms that have inhabited our little planet for
millions of years. Reinke ought, consistently, to admire the cosmic
intelligence of the Supreme Being in these movements of the cosmic
masses and its emanations, the "dominants," in the actual direction
of their movements, as much as he does in the plasma-flow in the tiny
organism.

The manifold gradation of vital movement which we find everywhere in
the higher organisms is not without expression even in the protist
realm. In this respect the chromacea, the simplest forms of vegetal
monera, and the bacteria, which we regard as corresponding animal
forms, developed from the former by metasitism, are of great interest.
As microscopic scrutiny fails to detect any purposive organization in
these unnucleated cells, and it is impossible to discover different
organs in their homogeneous plasma-body, we have to look upon their
movements as direct effects of their chemical molecular structure. But
the same must be said also of a number of nucleated cells, both among
the protophyta and the protozoa; only in this case the structure is
less simple, in so far as both the nucleus itself and the surrounding
cell-body exhibit, in indirect division, complicated movements in the
plasm (caryokinesis). Apart from these, however, there is nothing to
be seen in many unicellular beings (_e.g._, paulotomea, or calcocytea)
that we need call "vital movement." On the border between the organic
and inorganic worlds we have, as regards movement, the simplest forms
of the chromacea, chroococcacea. We can see no vital movement in
these structureless particles of plasm except slight changes of form,
which occur when they multiply by cleavage. The internal molecular
movements of the living matter, which effect their simple plasmodomous
metabolism and growth, lie beyond our vision. The reproduction itself,
in its simplest form of self-cleavage, seems to be merely a redundant
growth, exceeding the limit of individual size for the homogeneous
plasma-globule (_cf._ chapters ix. and x.).

The great majority of the protists have the appearance of real,
nucleated cells. Hence we have to distinguish two different forms
of movement in the unicellular organism--the inner movement in the
caryoplasm of the nucleus and the outer in the cytoplasm of the
cell-body; the two enter into close mutual relations during the
remarkable process of partial resolution of the nucleus (caryolysis).
In this modification and partial dissolution of their constituents we
observe, during indirect cell-division, certain complicated movements
(the significance of which is as yet entirely unknown), that are
accomplished by both the granules of chromatin and the threads of
achromin, and which are comprised under the head of nuclear movements
(caryokinesis). It has lately been attempted to explain them on purely
physical principles. The same may be said of the internal flow of the
plasm which we find in the plasmodia of the amœbæ and mycetozoa, and
in the endoplasm of many of the protophyta and protozoa.

The slow displacement of the molecules of plasm which is at the
bottom of these plasma-movements also causes a variety of external
changes of form in simple naked cells. Variable processes like folds
or fingers (the "fold-feet," _lobopodia_) appear on their surface. As
they are best observed in the common amœbæ (naked nucleated cells
of the simplest kind), they are called amœboid movements. With
these is connected the variable movement of the larger rhizopods, the
radiolaria and thalamophora, in which hundreds of fine threads radiate
from the surface of the naked plasma-body. A number of recent experts
on the rhizopods, such as Bütschli, Richard Hertwig, Rhumbler, and
others, have attempted to trace to purely physical causes this varying
formation of pseudopodia, and their branching and net-like structure
(without definite direction).

It is more difficult to do this in the case of the most highly
differentiated of the protozoa, the infusoria. With these the free
movement of the unicellular protozoon is farther advanced through
the formation of permanent hairlike processes (long single lashes in
the flagellata, and a number of short lashes in the ciliata) on the
cell-surface and the movement of these by contraction and expansion,
like the limbs, tentacles, and bones of the higher animals. The
apparent spontaneity and various modulation in the ever-changing
movements of these cell-feet is, in many of the infusoria, so like the
autonomous voluntary movements in the metazoa that several experts on
the infusoria have been moved on this account to ascribe individual
(and even conscious) souls to them. Hence the difference between the
various kinds of living movement is already very considerable before
we leave the kingdom of the protists. On the one hand, the lowest
monera (chromacea) join on directly to inorganic phenomena. On the
other hand, the highly differentiated infusoria (ciliata) show so
great a resemblance to the higher animals in their differentiated and
autonomous movements that they have been credited with the possession
of "free-will." There is no such thing as a sharp division.

In a large section of the higher protozoa differentiated organs of
movement are developed, which may be compared to the muscles of the
metazoa. In the cytoplasm threadlike, contractile structures are
formed, and these have, like the muscular fibres of the metazoa, the
power to contract and expand again in definite directions. These
myophæna or myonema form, in many of the infusoria, both ciliata
and flagellata, a special thin layer of parallel or crossed fibres
underneath the exoplasm or the hyaline skin-layer of the cell. The
metabolic body of the infusorium may be altered in various ways by the
autonomous contraction of these. Special instances of these myophæna
are the _myophrisca_ of the acantharia--contractile threads which
surround the radial needles of these radiolaria like a crown. They
are found in their outer gelatine envelope, the calymma, and by their
contraction extend it, and so lessen the specific gravity.

Many of the aquatic protophyta and protozoa have the power of
autonomous and independent locomotion, and this often has the
appearance of being voluntary. Among the simplest fresh-water
protozoa are the arcellina or thecolobosa (_difflugia_, _arcella_),
little rhizopods that are distinguished from the naked amœbæ by
the possession of a firm envelope. They usually creep about in the
slime at the bottom, but in certain circumstances rise to the surface
of the water. As Wilhelm Engelmann has shown, they accomplish this
hydrostatic movement by means of a small vesicle of carbonic acid,
which expands their unicellular body like an air-balloon; the specific
weight of the cell-body, which is of itself heavier than water, is
sufficiently lowered by this. The same method is followed by the pretty
radiolaria which live floating (as plankton) at various depths of the
sea. Their unicellular (originally globular) body is divided by a
membrane into a firm inner central capsule and a soft outer gelatine
covering. The latter, known as the calymma, is traversed by a number
of water-vesicles or vacuoles. As a result of an osmotic process,
carbonic acid may be secreted or pure water (without the salt of the
sea-water) be imbibed in these vacuoles; by this means the specific
gravity of the cell is lessened, and it rises to the surface. When
it desires to make itself heavier and sink, the vacuoles discharge
their lighter contents. These hydrostatic movements of the radiolaria
(for which the myophrisca, still more complicated structures, have
been developed in the acantharia) attain by simple means the same end
that is accomplished in the siphonophora and fishes by air-filled and
voluntarily contractile swimming-bladders.

Numbers of the unicellulars alter their position very
characteristically by secreting a thick mucus at one side of their body
and fastening this to the ground. If the secretion continues, a longish
jelly-like stalk is produced by which the cell slowly pushes itself
along, like a boat with a rowing-pole. This secretory locomotion is
found, among the protophyta, in the desmidiacea and diatomes, and in
some of the gregarinæ and rhizopods among the protozoa. The peculiar
rolling movements of the oscillaria (threadlike chains of blueish-green
unnucleated cells, closely related to the chromacea) are also effected
by the secretion of mucus. On the other hand, it is probable that the
sliding movements of many of the diatomes are due to fine processes
(vibratory hairs?) in the plasm, which proceed either out of the seams
(_raphe_) of the bivalvular silicious shells or through the fine pores
in them.

Especially important in the easy and rapid locomotion of many
unicellulars is the formation of fine hairlike processes at the surface
of the body; in the broadest sense, they are called vibratory hairs.
If only a few whiplike threads are formed, they are called _whips_
(_flagella_); if many short ones, _lashes_ (_cilia_). Flagelliform
movement is found in some of the bacteria, but especially in the
mastigophorous "whip-infusoria," in the mastigota among the protophyta,
and the flagellata among the protozoa. As a rule, we have in these
cases one or two (rarely more) long and very thin whip-shaped
processes, starting from one pole of the long axis of the oval, round,
or long cell-body. These whips (_flagella_) are set in vibratory motion
(apparently often voluntary) in various ways, and serve not only for
swimming or creeping, but also for feeling and securing food. Similar
whip-cells (_cellulæ flagellatæ_) are also found very commonly in the
body of tissue-animals, usually packed together in an extensive layer
at the inner or outer surface (ciliated epithelium). If single cells
are released from the group, they may live independently for some time,
continuing their movements and resembling free infusoria. The same may
be said of the travelling spores of many of the algæ, and of the most
remarkable of all ciliated cells--the spermia or spermatozoa of plants
and animals.

As a rule they are cone-shaped, having an oval or pear-shaped (though
often also rod-shaped) head, which tapers into a long and thin thread.
When their lively movements were first noticed in the male seminal
fluid (each drop of which contains millions of them) two hundred years
ago, they were thought to be real independent animalcules, like the
infusoria, and so obtained their name of seed-animals (spermatozoa).
It was a long time (sixty years ago) before we learned that they are
detached glandular cells, which have the function of fertilizing the
ovum. It was discovered at the same time that similar vibratory cells
are found in many of the plants (algæ, mosses, and ferns). Many of the
latter (for instance, the spermatozoids of the cycadea) have, instead
of a few long whips, a number of short lashes (_cilia_), and resemble
the more highly developed ciliated infusoria (_ciliata_).

The ciliary movement of the infusoria is held to be a more perfect form
of vibratory movement, because the many short lashes found on them are
used for different purposes, and have accordingly assumed different
forms in the division of labor. Some of the cilia are used for running
or swimming, others for grasping or touching, and so on. In social
combinations we have the ciliated cells of the ciliated epithelium of
the higher animals--for instance, in the lungs, nostrils, and oviducts
of vertebrates.

In the unicellular, non-tissue forming protists, all the vital
movements seem to be active functions of the plasm of the single
cell; but in the histona, the multicellular tissue-forming organisms,
they are the outcome of the combined movements of the many cells
which compose the tissue. Careful anatomic study and experimental
physiological scrutiny of the motor processes are, therefore, first
directed, in the case of the histona, to clearing up the nature and
activity of the special cells which compose the tissue, and then the
structure and functions of the tissue itself. When we start from this
point, and survey the manifold active motor phenomena of the histona
as a whole, we see at once an essential agreement in the phoronomy of
the two kingdoms of the metaphyta and metazoa, in the sense that at the
lower stages the chemical and physical character of the motor processes
can be clearly shown and can be traced to an interchange of energy in
the plasm of the cells that make up the tissue. In the higher stages,
however, we find striking differences, the voluntary character of many
autonomous movements being very conspicuous in the higher animals,
and thus the great problem of the freedom of the will is added to the
purely physiological questions of stimulated movement, growth-movement,
etc.

Moreover, the movements of the metazoa are much more varied and
complicated than those of the metaphyta, in consequence of the higher
differentiation of their sense-organs and the centralization of their
nervous system. The former have generally free locomotion and the
latter not. The special mechanism of the organs of movement is also
very different in the two groups. In most of the metazoa the chief
motor organs are the muscles, which have developed in the highest
degree the power of definitely directed contraction and expansion.
In most of the metaphyta, on the other hand, the chief part of the
movements depend on the strain of the living plasm, or what is called
the _turgor_ or expansibility of the plant-cells. This is effected
by the osmotic pressure of the internal cell-fluid and the elasticity
of the cellulose wall, which is thus expanded. Nevertheless, in both
cases--and in all "vital" phenomena--the real cause of the process is,
in the ultimate analysis, the chemical play of energy in the active
plasm.

The metaphyta, with few exceptions, are fixed in one spot for life, or
only mobile for a short time when they are young. In this they resemble
the lower metazoa, the sponges, polyps, corals, bryozoa, etc. They have
not free locomotion. The motor phenomena which we find in them affect
only special parts or organs. They are mostly reflex or paratonic,
and due to external stimuli. Only a few of the higher plants exhibit
autonomous or spontaneous movement, the stimulating cause of which is
unknown to us, and which may be compared to the apparently voluntary
actions of the higher animals. The lateral feather-leaves of an Indian
butterfly flower (_hedysarum gyrans_) move in circles through the air,
like a pair of arms swinging, without any external cause; they complete
a circle in a couple of minutes. Variations in the intensity of light
have no effect on them. Similar spontaneous movements of the leaves
of several species of clover (_trifolium_) and sorrel (_oxalis_) are
performed only in the dark, not in the light. The terminal leaf of
the meadow-clover repeats its rotation, which describes more than one
hundred and twenty degrees of an arc, every two to four hours. The
mechanical cause of these spontaneous "variation movements" seems to
lie in variations of expansibility.

Voluntary and autonomous turgescence-movements of this kind are only
observed in a few of the higher plants, but stimulated movements that
are accomplished by the same mechanism are very common in the vegetal
world. We have, especially, the well-known "sleep," or nyktitropic
movements, of many plants. Many leaves and flowers hold themselves
vertically to the streaming rays of the sun. When darkness comes on
they contract, and the calices of the flowers close. Many flowers are
open for only a few hours a day. The mechanism of turgescence, which
effects these swelling movements, consists in the co-operation of the
osmotic pressure of the internal cell-fluid and the elasticity of the
strained cell-membrane enclosing the cytoplasm. The strain of the outer
cellulose membrane on the plasmatic primordial sac within it grows so
much on the accession of osmotically active matter that the internal
pressure is equal to several atmospheres, and the elastic strained
membrane stretches from ten to twenty percent. When water is withdrawn
again from one of these swollen or turgescent cells, the membrane
contracts; the cell becomes smaller, and the tissue looser. Other
stimuli besides light (heat, pressure, electricity) may produce these
expansional variations, and, as a consequence of it, certain reflex
movements (or paratonic variational movements). The most striking and
familiar examples are the flesh-eating fly-trap (_dionæa muscipula_)
and the sensitive plant (_mimosa pudica_); their contraction is caused
by mechanical stimuli, shaking, pressure, or the touching of the leaves.

Most of the higher animals have the power of free and voluntary
locomotion. It is, however, wanting in some of the lower classes,
which spend the greater part of their life at the bottom of the water,
like plants. Hence these were formerly held to be vegetable--thus
the sponges, polyps, and corals among the cœlenteria. A number
of classes of the cœlomaria have also adopted the stationary
life, such as the bryozoa and the spirobranchia among the vermalia,
many mussels (oysters, etc.), the actinia among the tunicates, the
sea-lilies (_crinoidea_) among the echinoderms, and even highly
organized articulate, such as the tube-worms (_tubicolæ_), among the
annelids, and the crawling crabs (_cirripedia_), among the crustacea.
All these stationary metazoa move freely in their youth, and swim about
in the water as _gastrulæ_, or in some other larva form. They have
taken only gradually to stationary habits, and have been considerably
modified, and often greatly degenerated, in consequence; for instance,
in the loss of the higher sense-organs, the bones, and even of the
whole head. Arnold Lang has shown this very clearly in his excellent
work on the influence of stationary life on animals. The study of
these retrogressive metamorphoses is very important for the theory of
progressive heredity and selection; it also shows the great value of
free locomotion for the higher sensitive and intellectual development
of the animals and man.

In many of the lower aquatic metazoa the surface of the body is covered
with vibratory epithelium--that is to say, with a layer of skin-cells
which bear either one long whip (_flagellum_) or several short lashes
(cilia). Flagellated epithelium is especially found in the cnidaria
and platodes; ciliated epithelium mostly in the vermalia and mollusca.
As the lashing motion of these hairlike processes brings a constant
stream of fresh water to the surface of the body, they first of all
effect respiration through the skin. But in many of the smaller metazoa
they also serve the purpose of locomotion, as in the gastræads,
the turbellaria, the rotifera, the nemertina, and the young larvæ
of many other metazoa. The vibratory apparatus reaches its highest
development in the _ctenophora_. The extremely delicate and soft body
of these gherkin-shaped cnidaria swims slowly in the water by means
of the strokes of thousands of tiny oar-blades. They are arranged in
eight longitudinal rows which stretch from the mouth to the opposite
pole. Each oar-blade consists of the long hair-lashes of a group of
epithelial cells glued together.

The chief motor organs in the metazoa are the muscles which constitute
the "flesh" of the body. Muscular tissue consists of contractile
cells--that is to say, of cells with the sole property of contraction.
When the muscular cell contracts, it becomes shorter and its diameter
increases. This brings nearer together the two parts of the body to
which its ends are attached. In the lower metazoa the muscle-cells
have, as a rule, no particular structure; but in the higher animals the
contractile plasm undergoes a peculiar differentiation, which has the
appearance under the microscope of a transverse streaking of the long
cells. On this ground a distinction is drawn between striated muscles
and simple non-striated or smooth muscles. The more vigorous, rapid,
and definite is the contraction of the muscle, the more marked is the
streaky character, and the more pronounced the difference between the
doubly refractive muscular particles from the simple refractive. The
striated muscle is "the most perfect dynamo we know of" (Verworn). The
normal heart of a man accomplishes every day, according to Zuntz, a
work of about twenty thousand kilogrammetres--in other words, an energy
that would suffice to lift to a height of one metre a weight of twenty
thousand kilogrammes. In many flying insects (gnats, for instance) the
flying muscles make three hundred to four hundred contractions a second.

In the lower and higher classes of the metazoa the muscle amounts to
no more than a thin layer of flesh underneath the skin. This layer
consists of muscular cells, which come originally from the ectoderm
in the form of internal contractile processes of the skin-cells
themselves, as in the polyps. In other cases the muscle-cells are
developed from the connective-tissue cells of the mesoderm, the
middle skin-layer, as in the ctenophora. This mesenchymic muscle is
less common than epithelial muscle. In most of the askeletal vermalia
the subdermal muscle divides into two layers--an outer deposit of
concentric muscles and an inner layer of longitudinal muscles; in the
cylindrical worms (nematodes, sagittæ, etc.) the latter fall into
four longitudinal bands, one pair of upper (dorsal) and a pair of
lower (ventral) muscular bands. At those parts of the body which are
especially used for locomotion the muscle is more strongly developed,
as in the belly-side of the crawling worms and mollusks. This muscular
surface develops into a kind of fleshy "foot" (_podium_); it assumes
a great variety of forms in the various classes of mollusks. In most
of the snails which creep on the solid ground it grows into a muscular
"flat-foot" (_gasteropoda_); in the mussels which cut like a plough
through the soft slime it forms a sharp "hatchet-foot" (_pelecypoda_).
The keel-snails (_heteropoda_) swim by means of a "keel-foot," which
works like the screw of a ship; the floating-snails (_pteropoda_) swim
unsteadily (like butterflies flying) by means of a pair of head-folds,
which develop from the side of the anterior foot-section. In the
highest mollusks, the cuttle-fishes (_cephalopoda_), this fore-foot
divides into four or five pairs of folds, which grow into long and very
muscular "head-arms"; the numbers of strong suckers on the latter have
also special muscles. In all these non-articulate mollusks and vermalia
hard skeletons are either altogether wanting or (like the external
shells of the mollusks) they have no functional relation to the motor
muscles. It is otherwise in the higher animals, in which we find this
relation to a solid jointed skeleton that becomes a passive motor
apparatus.

The higher groups of the animal kingdom in which a characteristic solid
skeleton is developed and forms an important starting-point for the
muscles, as well as a support and protection for the whole body, are
the three stems of the echinoderms, articulates, and vertebrates.
All three groups are very rich in forms, and far surpass all the
other stems of the animal world in the perfection of their locomotive
apparatus. However, the disposition and development of the skeleton as
a passive support, and the correlation of the muscles to it as active
pulling-organs, differ very much in the three classes, and are the
chief factors in determining their characteristic types; they show
clearly (even apart from other radical differences) that the three
stems have arisen independently of each other from three different
roots in the vermalia-stem. In the echinoderms the calcareous skeleton
is formed from chalky deposits in the corium, in the articulates from
chitine secretions of the epidermis, and in the vertebrates from
cartilage of an internal chord-sheath (_cf._ _Anthropogeny_, chapter
xxvi.).

The remarkable stem of the sea-dwelling echinoderms or "prickly skins"
is distinguished from all the other animal groups by a number of
striking peculiarities; prominent among these are the special formation
of their active and passive motor organs and the curious form of their
individual development. In this ontogenesis two totally different
forms appear successively--the simple astrolarva and the elaborately
organized and sexually mature astrozoon. The small, free-swimming
astrolarva has the general structural features of the rotatoria, and
so shows, in accordance with the biogenetic law, that the original
stem-form of the echinoderms (the amphoridea) belonged to this group
of the vermalia. I have briefly explained these structures in the
_History of Creation_ (chapter xxii.), and more fully in my essay on
the amphoridea and cystoidea (1896). The little astrolarva has no
muscles, and no water-vessels or blood-vessels. It moves by means
of vibratory lashes or bands, which are attached to special armlike
processes at the surface. These arms are regularly developed to the
right and left of the bilateral symmetrical larva (which as yet shows
no trace of the five-rayed structure). By a very curious modification
the small bilateral astrolarva is transformed into the totally
different pentaradial astrozoon, the large sexually mature echinoderm
with a pronounced five-rayed structure. (See _Art-forms in Nature_,
plates 10, 20, 30, 40, 60, 70, 80, 90, and 95.) It has a most elaborate
organization, with muscles and cuticular skeleton, blood-vessels and
water-vessels, etc. A section of the astrozoa--the living crinoidea,
or sea-lilies, and the extinct classes of blastoidea (sea-buds),
cystoidea (sea-apples), and amphoridea (sea-urns)--grow in stationary
fashion at the bottom of the sea. The other four extant classes
creep about in the sea--the sea-gherkins (holothuria), the star-fish
(asteridea and ophoidea), and the sea-urchins (echinidea). Their
creeping motion is accomplished by two kinds of organs--water-feet
and skin-muscles. The latter find their support and attachment in
solid calcareous needles, which develop from chalky deposits in the
corium. As these calcareous needles (which are particularly conspicuous
in the sea-urchin) are set movably in special protuberances of the
calcareous plates of the cuticular skeleton, and moved by little
muscular needles, the echinoderms walk on them as if they were stilts.
Between these, however, a number of water-feet arise from inside--thin
tubes like the fingers of a glove, which are filled with water by
an internal conduit-system (the so-called ambulacral system) and
become stiff. These very extensible ambulacral feet, often provided
with a suctorial plate at the closed outer end, serve for creeping,
sucking, touching, and grasping. As these distinctive motor organs
of the echinoderms--both the ambulacral feet with their complicated
water-tubes and the movable needles with their joints and muscles--are
found in hundreds, often in thousands, on every individual five-rayed
astrozoon, we might say that the echinoderms have the most advanced
and complicated motor organs of all animals. Their historical
development is perfectly understood from its earliest stages, since
Richard Semon found, in his ingenious pentact æatheory (1888),
the correct phylogenetic meaning of the curious embryology of the
echinoderms discovered in 1845 by Johannes Müller. I endeavored in 1896
to establish it in detail, in relation to paleontological discoveries,
in the essay I have mentioned.

The large stem of the articulata (the richest in forms of all the
animal stems) comprises three chief classes--the annelids, crustacea,
and tracheata. All three groups agree in the essential features
of their organization, especially in the external articulation or
metamerism of the long bilateral body, and also in the repetition of
the internal organs in each joint or segment. In each joint there is
originally a knot of the ventral nervous system (the ventral marrow), a
chamber of the dorsal heart, a chitine-ring of the cutaneous skeleton,
and a corresponding group of muscles.

Of the three great classes of the articulates the annelids are
developed directly from the vermalia, of which both the nematoda and
nemertinæ approach very closely to them. The two other and more highly
organized classes, the crustacea and tracheata, are younger groups,
independently evolved from two different stems of the annelids. The
annelids, or "ringed-worms" (to which, _e.g._, the rain-worms belong),
have mostly a very homogeneous articulation; their segments or metamera
repeat the same structure to a great extent, especially the subdermal
muscles. In a transverse section we see in every joint underneath the
layer of concentric muscles a pair of dorsal and a pair of ventral
muscles. Their epidermis has secreted a thin covering of chitine, in
the tubular worms a leather-like or calcified tube. There are no bones
in the oldest annelids; in the younger bristle-worms (_polychæta_) one
or two pairs of short unjointed feet (_parapodia_) are found in every
joint.

The other two chief classes of the articulates develop long and jointed
feet of very varied forms, and at the same time assume different shapes
of limbs in the division of labor. This heterogeneous articulation
(heteronomy) is the more pronounced the higher the whole organization.
This is equally true of the aquatic, gill-breathing crustacea (crabs,
etc.) and the tracheata (terrestrial animals breathing through a
trachea, the myriopods, spiders, and insects). In the higher groups of
both classes the number of limbs is usually not higher than fifteen to
twenty; and they are distributed in three principal sections--head,
breast, and posterior part of the body. The firm covering of chitine,
which was delicate and thin in most of the annelids, is much thicker in
most of the crustacea and tracheata, and often hardened by a calcareous
deposit; it forms a solid ring of chitine in each segment, inside which
the motor muscles are attached. The successive hard rings are connected
by thin, mobile, intermediate rings, so that the whole body combines
firmness, elasticity, and mobility in a high degree. The structure of
the long jointed legs, which are fixed in pairs on each segment, is
very similar. Hence the typical character of the motor organs of the
crustacea lies in the circumstance that both in the body and the limbs
the muscles are attached to the interior of hollow chitine tubes, and
go in these from member to member.

The vertebrates are just the reverse in structure. In their case
a solid internal skeleton is formed in the longitudinal axis of
the body, and the muscles are external to these supporting organs.
The articulation or metamerism itself is not visible externally in
the vertebrates; it is only seen in the muscular system when the
non-articulated skin has been removed. Then, even in the lowest
skull-less vertebrates, the acrania, the internal skeleton of which
consists merely of a cylindrical, solid, and elastic axial rod
(_chorda_), we see on each side a row of muscular plates (fifty to
eighty in the amphioxus). In this case there are not pairs of limbs,
and it is the same with the oldest craniate animals, the cyclostoma
(myxinoida and petromyzonta). It is only with the third class of the
vertebrates, the true fishes (_pisces_), that two pairs of lateral
limbs appear--the breast-fins and belly-fins. From these, in their
terrestrial descendants, the oldest amphibia of the Carboniferous
Period, the two pairs of jointed legs--fore-legs (carpomela) and
hind-legs (tarsomela)--are derived. These four lateral five-toed legs
have a very characteristic and complicated articulation, both in the
internal bony skeleton and the muscular system that encloses this and
is attached to it. From the amphibia, the earliest quadrupeds, this
locomotive apparatus is transmitted by heredity to their descendants,
the three higher classes of the vertebrates, reptiles, birds, and
mammals. As I have dealt with these important structures fully in my
_Anthropogeny_ (chapter xxvi.), and given a number of illustrations of
them, I must refer the reader to that work,[8] and will only make a few
observations on the mammals.

Both parts of the motor apparatus, the internal bony skeleton (the
passive supporting apparatus) and the external muscular system (the
active motor), exhibit a great variety of construction within the
mammal class, in consequence of adaptation to the most different
habits and functions. We have only to compare the running carnivora
and ungulata, the leaping kangaroos and jerboas, the burrowing moles
and hyperdæi, the flying cheiroptera and bats, the fishlike swimming
sirens and whales, and climbing lemures and apes. In all these and the
remaining orders of the mammals the whole regular structure of the
motor apparatus is strikingly adapted to the habits of life which have
been formed by this adaptation itself. Nevertheless, we see that the
essential character of the inner organization which distinguishes the
mammals as a class is not affected by this adaptation, but constantly
maintained by heredity. These recognized facts of comparative anatomy
and ontogeny, and the concordant results of paleontology, prove
convincingly that all living and fossil mammals, from the lowest
ungulates and marsupials to the ape and man, have descended from one
common stem-form, a pro-mammal, that lived in the Triassic Period;
its earlier ancestors in the Permian Period were reptiles, and, in
the Carboniferous Period, amphibia. Among the characters of the
locomotive apparatus which are peculiar to mammals we have, on the
one hand, the structure of the vertebral column and the skull, and,
on the other hand, the formation of the muscles which are attached
to these supporting organs. In the skull we particularly notice the
formation of the lower jaw and the joint by which it is connected with
the temporal bone. This joint is temporal, and so distinguished from
the square joint of the other vertebrates. The latter is found in the
mammals in the tympanic cavity of the middle-ear, between the hammer
(the modified joint of the lower jaw, _articulare_) and the anvil (the
original _quadratum_). In harmony with this remarkable modification
of the maxillary joint, the corresponding muscles have naturally
also undergone a considerable transformation. A distinctive muscle
that is only found in the mammals and regulates their respiration is
the diaphragm, which completely divides the abdominal and thoracic
cavities; the various muscles, from the blending of which it has been
formed, still remain separate in the other vertebrates.

The many organs by means of which our human organism accomplishes its
manifold movements are just the same as in the apes, and the mechanism
of their action is in no way different. The same two hundred bones,
in the same order and composition, form our internal bony skeleton;
the same three hundred muscles effect our movements. The differences
we find in the form and size of the various muscles and bones (and
which are, as is well known, also found between lower and higher
races of men) are due to differences in growth in consequence of
divergent adaptation. On the other hand, the complete agreement in the
construction of the whole motor apparatus is explained by heredity from
the common stem-form of the apes and men. The most striking difference
between the movements of the two is due to man's adaptation to the
erect posture, while the climbing of trees is the normal habit of the
ape. However, it is unquestionable that the former is an evolution
from the latter. A double parallel to this modification is seen in the
jerboa among the ungulates, and in the kangaroo among the marsupials.
Both these, in springing, use only the strong hinder extremities, and
not the weaker fore-limbs; as a result of this their posture has become
more or less erect. Among the birds we have an analogous case in the
penguins (_aptenodytes_); as they no longer use their atrophied wings
for flight, but only in swimming, they have developed an erect posture
when on land.

The human will is also not specifically different from that of the ape
or any other mammal; and its microscopic organs, the neurona in the
brain and the muscular cells in the flesh, work with the same forms
of energy, and are similarly subject to the law of substance. Hence
it is immaterial for the moment whether one believes in the freedom
of the will according to the antiquated creed of indeterminism, or
whether one holds it to be refuted scientifically by the arguments
of modern determinists; in either case the acts of the will and
voluntary movements follow the same laws in man as in the ape. The high
development of the function in civilized man, the ample differentiation
of speech and morality, art and science--in a word, the ethical
significance of the will for higher culture--is in no way discordant
to this monistic and zoologically grounded conception. In the lower
races these privileges of the civilized will are only found in a slight
degree, and some of them are wholly wanting among the lowest races. The
distance between the lowest savage and the most civilized human being
is greater, in this respect also, than that which separates the savage
from the anthropoid ape. However, I refer the reader to the remarks
I made at the close of the seventh chapter of the _Riddle_ on the
problem of the freedom of the will and the infinite literature relating
thereto. The reader who desires to go further into this subject will
find it well treated in the works of Traugott Trunk (1902) and Paul Rée
(1903) [also in Dr. Stout's recent little manual of psychology and Mr.
W. H. Mallock's _Religion as a Credible Doctrine_].




XIII

SENSATION

 Sensation and consciousness--Unconscious and conscious
 sensation--Sensibility and irritability--Reflex sensation and
 perception of stimuli--Sensation and living force--Reaction
 to stimuli--Resolution of stimuli--External and internal
 stimuli--Conveyance of stimuli--Sensation and striving--Sensation
 and feeling--Inorganic and organic sensation--Light sensation,
 phototaxis, sight--Sensation of warmth, thermotaxis--Sensation of
 matter, chemotaxis--Taste and smell--Erotic chemicotropism--Organic
 sensations--Sensation of pressure--Geotaxis--Sensation of
 sound--Electric sensation.


Sensation is one of those general terms that have at all times been
liable to the most varied interpretations. Like the cognate idea of
the "soul," it is still extremely ambiguous. During the eighteenth
century it was generally believed that the function of sensation was
peculiar to animals, and was not present in plants. This opinion found
its most important expression in the well-known principle in Linné's
_Systema Naturæ_: "Stones grow: plants grow and live: animals grow,
live, and feel." Albrecht Haller, who gathered up all the knowledge
of his time relating to organic life in his _Elementa Physiologiæ_
(1766), distinguished as its two chief characters "sensibility" and
"irritability." The one he ascribed exclusively to the nerves, and the
other to the muscles. This erroneous idea was subsequently refuted, and
in our own time irritability is conceived to be a general property of
all living matter.

The great advance made by the comparative anatomy and experimental
physiology of animals and plants in the first half of the nineteenth
century brought to light the fact that irritability or sensibility is
a common quality of all organisms, and that it is one of the principal
characteristics of vital force (_cf._ chapter ii.). The greatest merit
in connection with its experimental study attaches to the famous
Johannes Müller. In his classical _Manual of Human Physiology_ (1840)
he established his theory of the specific energy of the nerves and
their dependence on the sense-organs on the one hand and the mental
life on the other. He devoted the fifth chapter of his book to the
former and the sixth to the latter, approaching particularly to
Spinoza in his general psychological views; he treated psychology as
a part of physiology, and thus put on a sound scientific basis that
naturalistic conception of the place of psychology in the biological
system which we now regard as the correct view. At the same time he
proved that sensation is a function of the organism as much as movement
or nutrition.

The view of sensation that prevailed in the second half of the
nineteenth century was very different. On the one hand the experimental
and comparative physiology of the sense-organs and the nervous system
immensely enriched our exact knowledge by the invention of ingenious
methods of research and the use of the great advance made by physics
and chemistry. The famous investigations of Helmholtz and Hertwig on
the physics of the senses, of Matteucci and Dubois-Reymond on the
electricity of the muscles and nerves, and the great progress made in
vegetal physiology by Sachs and Pfeffer, and in physiological chemistry
by Moleschott and Bunge, enabled us to realize that even the most
mysterious of the wonders of life depend on physical and chemical
processes. By the application of the different stimuli--light, heat,
electricity, and chemical action--to the various sensitive or irritable
organs under definitely controlled conditions, scientists succeeded in
subjecting with exactness a great part of the phenomena of stimulation
to mathematical measurements and formulæ. The science of the stimuli
and their effects acquired a strictly physical character.

On the other hand, in most striking contradiction to the immense
advance of experimental physiology, we see that the general
conception of the various vital processes, and especially of the
inner nerve-action that converts the functions of the senses into
mental life, is most curiously neglected. Even the fundamental idea
of sensation, which plays the chief part in it, is disregarded more
and more. In many of the most valuable modern manuals of physiology,
containing long chapters on stimuli and stimulation, there is little or
no mention of sensation as such. This is chiefly due to the mischievous
and unjustifiable gulf that has once more been artificially created
between physiology and psychology. As the "exact" physiologists
found the study of the inner psychic processes which take place in
sense-action and sensation inconvenient and unprofitable, they gladly
handed over this difficult and obscure field to the "psychologists
proper"--in other words, to the metaphysicians, who had for the
starting-point of their airy speculations the belief in an immortal
soul and divine consciousness. The psychologists readily abandoned the
inconvenient burden of experience and _a posteriori_ knowledge, to
which the modern anatomic physiology of the brain laid special claim.

The greatest and most fatal error committed by modern physiology in
this was the admission of the baseless dogma that all sensation must
be accompanied by consciousness. As most physiologists share the view
of Dubois-Reymond, that consciousness is not a natural phenomenon,
but a hyperphysical problem, they leave it and this inconvenient
"sensation" outside the range of their researches. This decision is,
naturally, very agreeable to the prevalent metaphysics; it has just as
much interest in the transcendental character of sensation as in the
liberty of the will, and thus the whole of psychology passes from the
empirical province of natural science into the mystical province of
mental science. For its foundation they then take the "critical theory
of knowledge," which ignores the results of the real physiological
organs--the senses, nerves, and brain--and draws its "superior wisdom"
from the inner mirroring of self by the introspective analysis of
presentations and their associations. It is extraordinary that even
distinguished monistic physiologists suffer themselves to be taken
in with this sort of metaphysical jugglery, and dismiss the whole of
psychology from their province; their psychomonism readmits the soul as
a supernatural entity, and delivers it, in contrast with the "world of
bodies," from the yoke of the law of substance.

Impartial reflection on our personal experience during sensation and
consciousness will soon convince us that these are two different
physiological functions, which are by no means necessarily associated;
and the same may be said of the third principal function of the
soul--the will. When we learn an art--for instance, painting or
playing the piano--we need months of daily practice in order to become
expert at it. In this we experience every day hundreds of thousands
of sensations and movements which are learned and repeated with full
consciousness. The longer we continue the practice and the more we
adapt and accustom ourselves to the function, the easier and less
conscious it becomes. And when we have practised the art for some
years, we paint our picture or play our piano unconsciously; we think
no longer of all the small, subtle shades of sensation and acts of
will which were necessary in learning. The mere impulse of the will to
paint the picture once more or play the piece again suffices to release
the whole chain of complicated movements and accompanying sensations
which had originally to be learned slowly, laboriously, and with
full consciousness. An experienced pianist plays the most difficult
piece--if he has learned it and repeated it thousands of times--"half
in a dream." But it needs only a slight accident, such as a mistake
or a sudden interruption, to bring back the wandering attention to
the work. The piece is now played with clear consciousness. The same
may be said of thousands of sensations and movements which we learned
at first consciously in childhood, and then repeat daily afterwards
without noticing--such as in walking, eating, speaking, and so on.
These familiar facts prove of themselves that consciousness is a
complicated function of the brain, by no means necessarily connected
with sensation or will. To bind up the ideas of consciousness and
sensation inseparably is the more absurd, as the mechanism or the real
nature of consciousness seems very obscure to us, while the idea of it
is perfectly clear: we know that we know, feel, and will.

The word "irritability" is generally taken by modern physiology to mean
that the living matter has the property of reacting on stimuli--that
is to say, of responding by changes in itself to changes in its
environment. The stimulus, or action of a foreign energy, must,
however, be felt by the plasm before the corresponding stimulated
movement (in the form of various manifestations of energy) will be
produced. Hence the question whether this sensation is (in certain
cases) associated with consciousness or (generally) remains unconscious
is of a subordinate interest. The plant that is caused to open its
floral calyx by the stimulus of light acts just as unconsciously in
this as the coral that spreads out its crown of tentacles under the
same influence; and when the sensitive carnivorous plant (_dionæa_ or
_drosera_) closes its leaves in order to catch and destroy the insect
sitting on them, it acts in the same way as the sensitive actinia or
coral when it draws in its crown of tentacles for the same object--in
both cases without consciousness! We call these unconscious movements
"reflex actions." I have dealt somewhat fully with these reflex
movements in the seventh chapter of the _Riddle_, and must refer the
reader thereto. This elementary psychic function always depends on
a conjunction of sensation and movement (in the widest sense). The
movement that the stimulus provokes is always preceded by a sensation
of the influence exerted.

Modern physiology makes desperate efforts to avoid the use of the
word "sensation" and substitute for it "perception of stimulus." The
chief blame for this misleading expression is due to the arbitrary
and unjustified separation of psychology from physiology. The latter
is supposed to occupy itself with the material phenomena and physical
changes, leaving to psychology the privilege of dealing with the
higher mental phenomena and metaphysical problems. As we reject this
distinction altogether on monistic principles, we cannot consent
to separate sensation from the perception of stimuli--whether this
sensation be accompanied with consciousness or not. Moreover, modern
physiology, in spite of its desire to keep clear of psychology, sees
itself compelled in a thousand ways to use the words "sensation" and
"sensitive," especially in the science of the organs of sense.

What we call sensation or perception of stimuli may be regarded
as a special form of the living force or actual energy (Ostwald).
Sensitiveness or irritability, on the other hand, is a form of virtual
or potential energy. The living substance at rest, which is sensitive
or irritable, is in a state of equilibrium and indifference to its
environment. But the active plasm, that receives and feels a stimulus,
has its equilibrium disturbed, and corresponds to the change in its
environment and its internal condition. This response of the organism
to a stimulus is called "reaction"--a term that is also used (in
the same sense) in chemistry to express the interaction of bodies
on each other. At each stimulation the virtual energy of the plasm
(sensitiveness) is converted into living or kinetic force (sensation).
The share of the stimulus in this conversion is described as a
"release" of energy.

The term "reaction" stands in general for the change which any body
experiences from the action of another body. Thus, for instance, to
take the simplest case, the interaction of two substances in chemistry
is called a reaction. In chemical analysis the word is used in a
narrower sense to denote that action of one body on another which
serves to reveal its nature. Even here we must assume that the two
bodies feel their different characters; otherwise they could not act
on each other. Hence every chemist speaks of a more or less "sensitive
reaction." But this process is not different in principle from the
reaction of the living organism to outer stimuli, whatever be their
chemical or physical nature. And there is no more essential difference
in psychological reaction, which is always bound up with corresponding
changes in the psychoplasm, and so with a chemical conversion of
energy. In this case, however, the process of reaction is much more
complicated, and we can distinguish several parts or phases of it:
1, the outer excitation; 2, the reaction of the sense-organ; 3, the
conducting of the modified impression to the central organ; 4, the
internal sensation of the conducted impression; and, 5, consciousness
of the impression.

The important idea of a release of energy--the term we give to the
effect of the stimulus--is also used in physics. If we put a piece of
burning wood in a barrel of powder, the flame causes an explosion. In
the case of dynamite a simple mechanical shock is enough to produce
the most enormous expenditure of force in the explosive matter. When
we discharge a bow the slight pressure of the finger on the tense
cord suffices to send out the arrow or bolt on its deadly mission. So
also a sound or a ray of light that strikes the ear or eye suffices
to bring about a number of complex effects by means of the nervous
system. In the fertilization of the ovum by the male sperm the chemical
conjunction of the two formative principles is sufficient to cause the
growth of a new human being out of the microscopic plasma-globule, the
stem-cell (_cytula_). In these and thousands of other reactions a very
slight shock suffices to provoke the largest effects in the stimulated
substance. This shock, which we call a release of energy, is not the
direct cause of the considerable result, but merely the occasion for
bringing it about. In these cases we have always a vast accumulation
of virtual energy converted into living force or work. The magnitude
of the two forces has no relation at all to the smallness of the shock
which led to the conversion. In this we have the difference between
stimulated action and the simple mechanical action of two bodies on
each other, in which the quantity of the energy expended is equal on
both sides, and there is no stimulus.

The immediate effect of a stimulus on living matter can best be
followed in external physical or chemical stimuli, such as light,
heat, pressure, sound, electricity, and chemical action. In these
cases physical science is often able to reduce the life-process to the
laws of inorganic nature. This is more difficult with the internal
stimuli within the organism itself, which are only partly exposed
to physiological investigation. It is true that here also the task
of science is to reduce all the biological phenomena to physical and
chemical laws. But it can only discharge a part of this difficult task,
as the phenomena are too complicated, and their conditions too little
known in detail, to say nothing of the crudeness and imperfectness of
our methods of research. Yet, in spite of all this, comparative and
phylogenetic physiology convinces us that even the most complicated
of our internal excitations, and particularly the mental activity of
the brain, depend just as much as the outer stimulations on physical
processes, and are equally subject to the law of substance. This is, in
fact, true of reason and consciousness.

In man and all the higher animals the stimuli are received by the
organs of sense and conducted by their nerves to the central organ. In
the brain they are either converted into specific sensations in the
sense-centres, or conveyed to the motor region, where they provoke
movements. The conduction of stimuli is simpler in the lower animals
and the plants; the tissue-cells either directly affect each other or
are connected by fine threads of plasm. In the unicellular protists
the stimulus which strikes one particular spot of the surface may be
immediately communicated to the other parts of the unified plasmic body.

We shall see in the course of our inquiry that the simplest form of
sensation (in the widest sense) is common to inorganic and organic
bodies, and thus that sensitiveness is really a fundamental property
of all matter, or, more correctly, all substance. We may, therefore,
ascribe sensation to the constituent atoms of matter. This fundamental
thought of hylozoism, expressed long ago by Empedocles, has lately
been very definitely urged, especially by Fechner. However, the able
founder of psychophysics (_cf._ the _Riddle_, p. 35) assumes that
consciousness (or thought, in the Spinozistic sense) always accompanies
this universal property of sensation. In my opinion, consciousness is a
secondary psychic function, only found in man and the higher animals,
and bound up with the centralization of the nervous system. Hence it is
better to speak of the unconscious sensation of the atoms as _feeling_
(_æsthesis_), and their unconscious will as _inclination_ (_tropesis_).
It finds expression in the one-sided action of a stimulus as a
"directed movement" or "stimulated movement" (_tropismus_ or _taxis_).

The familiar ideas of sensation and feeling are often confused, and
employed in very different ways in both physiology and psychology. The
metaphysical tendency which so completely separates the two sciences,
and the physiological tendency which agrees with it, regard feeling
as a purely psychic or spiritual function, whereas in the case of
sensation they have to admit the connection with bodily functions,
especially sense-action. In my opinion, the two ideas are purely
physiological and cannot be sharply separated, or only in the sense
that sensation relates more to the external (objective) part of the
sensory nerve-process, and feeling to the internal (subjective) part.
Hence we may define the difference in a general way by saying that
sensation perceives the different qualities of the stimuli, and feeling
only the quantity, the positive or negative action of the stimulus
(pleasure or pain). In this last and widest sense we may ascribe
the feeling of pleasure and pain (in the contact with qualitatively
differing atoms) to all atoms, and so explain the elective affinity in
chemistry (synthesis of loving atoms, inclination; analysis of hating
atoms, disinclination).

Our monistic system (whether it be taken as energism or materialism,
or more correctly as hylozoism) regards all substance as having
"soul"--that is to say, endowed with energy. In the chemical analysis
of organisms we do not find any elements that are not found in
inorganic nature; we find that the movements in organisms obey the
same laws of mechanics as the latter; we believe that the conversion
of energy in the living matter occurs in the same way, and is provoked
by the same stimuli, as in inorganic matter. We are forced to conclude
from. these experiences that the perception of stimuli--sensation in
the objective and feeling in the subjective sense--is also generally
present in the two. All bodies are in a certain sense "sensitive." It
is just in this dynamic conception of substance that monism differs
essentially from the materialistic system, which regards one part of
matter as "dead" and insensitive. In this we have the best means of
joining consistent materialism or realism with consistent spiritualism
or idealism. But, as a first condition of such a union, we must demand
a recognition that organic life is subject to the same general laws
as inorganic nature. In both cases the outer world acts alike as
a stimulus on the inner world of the body. We can easily see this
if we glance at the various kinds of sensation which correspond to
the various kinds of stimuli. Light and heat, external and internal
chemical stimuli, pressure and electricity, cause analogous sensations
and modifications in their effect on organic and inorganic bodies.

The effect which the light-stimulus has on living matter, the sensation
of light that results, and the chemical changes of energy that follow,
are of great physiological importance in all organisms. We might even
say that sunlight is the first, oldest, and chief source of organic
life; all other exertions of force depend in the long run on the
radiant energy of sunlight. The oldest and most important function
of plasm--one which is at the same time a cause of its formation--is
carbon-assimilation; and this plasmodomism is directly dependent on
sunlight. If it acts in a one-sided way, it causes the particular form
of stimulation which we call phototaxis or heliotropism. This is of a
positive character--that is to say, they turn towards the source of the
light--in the great majority of organisms, both protists and histona.
Everybody knows that flowers that are growing in the window of a room
turn to the light. However, many organisms which have grown accustomed
to living in the dark are heliotropically negative; they shun the light
and seek darkness, such as the fungi, many lucifugous mosses and ferns,
and many deep-sea animals.

The principal organs of light-sensation in the higher animals are the
eyes; they are wanting in many of the lower animals as well as the
plants. The essential difference between the real eye and a part of
the skin that is merely sensitive to light is that the eye can form a
picture of objects in the outer world. This faculty of vision begins
with the formation of a small convergent lens, a biconvex refracting
body at a certain spot on the surface. Dark pigment-cells which
surround it absorb the light-rays. From this first phylogenetic form of
the organ of vision up to the elaborate human eye there is a long scale
of evolutionary stages--not less extensive and remarkable than the
historical succession of artificial optical instruments from the simple
lens to the complicated modern telescope or microscope. This great
"wonder of life"--the long scale of the evolution of the eye--has an
interesting tearing on many important questions of general physiology
and phylogeny. We can, in this case, see clearly how a very complicated
and purposive apparatus can arise in a purely mechanical way, without
any preconceived design or plan. In other words, we can see how an
entirely new function--and one of its principal functions, vision--has
arisen in the organism by mechanical means.

The advanced vision of the higher animals is made up of a great number
of different functions, with a corresponding complexity of detail in
the anatomic structure of the eye. No other organ, after the brain,
is so necessary as the eye for the multifarious vital activities of
the higher animals, and especially for the mental life of civilized
man and the progress of art and science. What would the human mind be
if we could not read, write, and draw, and have a direct knowledge
through the eye of the forms and colors of the outer world? Yet this
invaluable structure is only the highest and most perfect stage in
the long chain of evolutionary processes which has its starting-point
in the general sensitiveness to light, or the photic irritability of
plasm. However, we find a number of varieties and grades of this even
among the unicellular protists, and, indeed, the very lowest and oldest
of the protists, the monera. Various species of both the chromacea and
the bacteria are heliotropic to different degrees, and have a fine
sensitiveness to the strength of the light stimulus.

The stimulating effect which light has on the homogeneous plasm of the
monera is also found in a number of inorganic bodies. In these cases
the photic stimulus produces partly chemical and partly mechanical
changes. Every chemist speaks of substances that are more or less
"sensitive" to light; the photographer speaks of his "sensitive
plates," the painter of his "sensitive colors." Many chemical compounds
are so sensitive to light that they are destroyed at once in sunlight,
and so have to be kept in the dark. There is no other word but
"sensation" to express the attitude of the atoms towards each other
which becomes so conspicuous in these cases under the influence of
sunlight. It seems to me that this phenomenon is a clear justification
of our hylozoic monism when it affirms that all matter is psychic. In
metaphysics sensation is held to be an essential property of the soul.

In the same general way as light the heat-stimulus acts on organisms,
and causes the sensations, sometimes pleasant and sometimes unpleasant,
which we call the subjective feeling of heat, warmth, coolness, or
cold. The sense-organ that receives these impressions of temperature is
the surface of the unicellular plasmic body in the protists, and the
skin (epidermis) that protects the surface from the outer world in the
histona. In all living things the temperature of the surrounding medium
(water or air) has a great influence in regulating the life-processes;
in the stationary animals and plants it is the temperature of the
ground to which they are attached. This temperature must always be
between the freezing-point and boiling-point of water, as fluid water
is indispensable for the imbibition of the living matter and the
molecular movements within the plasm. At the same time, some of the
lower protists (chromacea, bacteria) can endure very high and very
low temperatures, but only for a short time. Some protists (monera
and diatomes) can stand a temperature of 200° C. for several days,
and others can be heated above boiling-point without being killed.
Arctic and High-Alpine plants and animals may be in a frozen condition
for several months, yet live again when they are thawed. However, the
resistance to these extremes of cold lasts for only a limited time, and
in the frozen state all vital functions are at a standstill.

In the great majority of living things the vital activity is confined
within narrow limits of temperature. Many plants and animals in the
tropics which have been accustomed for thousands of years to the
constancy of the hot equatorial climate can endure only very restricted
variations of temperature. On the other hand, many of the inhabitants
of Central Siberia, where the climate is very hot in the short summer
and very cold in the long winter, can stand great variations. Thus
the living plasm has experienced considerable changes in its sense
of warmth through adaptation to different environments; not only the
maximum and the minimum, but the optimum (most agreeable point),
is subject to very great variations. This can easily be observed
and followed experimentally in the phenomena of thermotaxis or
thermotropism--that is to say, the effect that follows from a one-sided
action of the heat-stimulus. The organism that falls below the minimum
of temperature is said to be stiff with cold, while the organism that
rises above the maximum is stiff with heat.

The heat-stimulus acts on inorganic as well as organic bodies, like
the light-stimulus. The law holds good in both cases that higher
temperatures increase sensation, while lower ones paralyze it. There is
a minimum, an optimum, and a maximum, for many chemical and physical
processes in the inorganic world. As far as the melting effect of water
is concerned, freezing is the minimum of the heat stimulus and boiling
the maximum. As the various chemical compounds meet in water at very
different temperatures, we have an optimum for many substances--that is
to say, a degree of warmth which is most favorable to the solution of
a given quantity of a solid body in water. On the whole, the law holds
for chemical processes that they are accelerated by high temperatures
and retarded by low ones (like the human passions!); the former have
a stimulating and the latter a benumbing effect. As the action of the
various chemical compounds on each other is determined by the nature
of the elements and their affinities, we must trace the variations in
their conduct towards thermic stimuli to a sensation of temperature in
the constituent atoms; increase of temperature stimulates it, while
decrease lessens or paralyzes it. Here, again, the simple inorganic
processes have a general resemblance to the complicated vital phenomena
in the organic body.

Since we regard the whole of organic life as, in the ultimate analysis,
merely a very elaborate chemical process, we shall quite expect that
chemical stimuli are the most important factors in sensation. And this
is so in point of fact; from the simplest moneron up to the most highly
differentiated cell and on to the flower in the plant and the mental
life of man, the vital processes are dominated by chemical forces and
conversions of energy, which are set in play by external or internal
chemical stimuli. The excitation which they produce is called, in a
general way, "sensation of matter" or chemæsthesis; the basis of it
is the mutual relation of the chemical elements which we describe as
chemical affinity. In this affinity we have the play of attractive
forces which lie in the nature of the elements themselves, especially
in the peculiar properties of their constituent atoms; and this cannot
be explained unless we ascribe unconscious sensation (in the widest
sense) to the atoms, an inherent feeling of pleasure and the reverse,
which they experience in the contact of other atoms (the "loves and
hatreds of the elements" of Empedocles).

The numbers of different stimuli that act chemically on the plasm
and excite its "sensation of matter" may be divided into two
groups--external and internal stimuli. The latter lie within the
organism itself, and cause the internal "organic sensations";
the former are in the outer world, and are felt as taste, smell,
sex-impulse, etc. In the higher animals special chemical sense-organs
have been developed for these chemical stimuli. As these are well known
to us from our own human experience, and comparative physiology shows
us the same structures in the higher animals, we will deal first with
them. In general the same law holds for these external chemical stimuli
as for optical and thermic stimuli; we can recognize a maximum limit
of their action, a minimum below which they fail to stimulate, and an
optimum or stage in which their influence is strongest.

The important part played in human life by taste and the pleasure
associated with it is well known. The careful choice and preparation
of savory food--which has become an art in gastronomy and a branch
of practical philosophy in gastrosophy--was just as important two
thousand years ago with the Greeks and Romans as it is to-day in royal
banquets or the Lucullic dinners of millionaires. The excitement that
we see associated with this refined combination of rich foods and
drinks, and that finds expression in so many speeches and toasts, has
its philosophic root in the harmony of gustatory sensations and the
varying play of stimuli that the delicate dishes and wines exercise
on the organs of taste, the tongue and palate. The microscopic organs
of these parts of the mouth are the gustatory papillæ--cup-shaped
structures, covered with spindle-shaped "taste-cells," and having a
narrow opening into the cavity of the mouth. When sapid matters, drinks
and fluid or loose particles of food, touch the taste-cells, they
excite the fine terminal branchlets of the gustatory nerve which enters
the cells. As we find that there are similar structures in most of the
higher animals, and that they also choose their food with some care,
we may confidently assume that they have sensations of taste like man.
However, no trace of this is found in many of the lower animals; in
these cases it is impossible to lay down a line of demarcation between
taste and smell.

In man and the higher air-breathing vertebrates the seat of the sense
of smell is in the nostrils; in man it is especially that part of the
mucous lining of the nasal cavity which we call the "olfactory region"
(the uppermost part of the nasal dividing wall, the superior and middle
meatus). It is necessary for a sensation of smell that the odorous
matter, or olfactory stimuli, be brought in a finely divided condition
over the moist olfactory membranes. When they touch the olfactory
cells--slender, rod-shaped cells with very fine hairs at the free
end--they excite the ends of the olfactory nerve which are connected
with the cells.

In many animals, especially mammals, the sense of smell has a much more
important part in life than it has in man, in whom it is relatively
feeble. It is well known that dogs and other carnivora, and even
ungulates, have a much keener smell. In these cases the nasal cavity,
which is the seat of the sense, is much larger, and the muscles in it
are much stronger. The nostrils of the air-breathing vertebrates have
been developed from a pair of open nasal depressions in the skin of
the fish's head. But in these aquatic vertebrates the chemical action
of the olfactory stimuli must be of a different character, like the
sensation of taste. The odorous matter is, in these cases, brought
into contact with the olfactory membrane in a liquid form (in which
condition it is not perceptible to man). In fact, the division between
the senses of smell and taste disappears altogether in the lower
animals. These two "chemical senses" are closely related, and have a
common feature in the direct chemical action of the stimulus on the
sensitive part of the skin.

A chemical sensation of matter that corresponds completely to the real
taste-sensation in the higher animals is found in some of the higher
carnivorous plants. The leaves of the sun-dew (_drosera rotundifolia_)
are very sensitive insect-traps, and are armed at the edge with
knob-like tentacles, sticky hairs that secrete an acid, flesh-digesting
juice. When a solid body (but not a raindrop) touches the surface of
the leaf the stimulus acts in such a way on the tentacle heads as to
contract the leaf. But the acid fluid which serves for digestion,
and corresponds to the gastric juice in the animal, is only secreted
by the corpuscles if the solid foreign body is nitrogenous (flesh or
cheese). Hence the leaves of these insectivorous plants taste their
meat diet, and distinguish it from other solids, to which they are
indifferent. In the broader sense, in fact, we may describe the points
of the roots of plants as organs of taste; they plunge into the richer
parts of the earth which yield more nourishment, and avoid the poor
parts. In unicellular plants and animals the action of chemical stimuli
is especially conspicuous when it is one-sided, and provokes definite
movements in one particular direction (_chemotaxis_).

The movements of unicellular organisms that are provoked by chemical
stimuli and are known as chemotropism (more recently as chemotaxis) are
particularly interesting because they show the existence of a chemical
sensitiveness, somewhat resembling taste or smell, in the lowest
organisms, and even in the homogeneous plasm of the monera. Repeated
experiments of Wilhelm Engelmann, Max Verworn, and others, have shown
that many bacteria, diatomes, infusoria, rhizopods, and other protists,
have a similar sense of taste; they move towards certain acids (for
instance, a drop of malic acid) or a bubble of oxygen that lies on
one side of the drop of water in which the protists are under the
microscope. Many pathogenetic bacteria secrete poisonous substances
which are very injurious to the human frame. The active white
blood-cells, leucocytes, in the human blood have a special "taste" for
these bacteria-poisons, and concentrate in large quantities, by means
of their amœboid movements, at those parts of the body where they
are secreted. If the leucocytes prove the stronger in their struggle
with the bacteria, they destroy them, and in this way they act as
sanitary officers in keeping poisonous infection out of our organism.
But if the bacteria win the battle, they are transported into other
parts of the body by the leucocytes; they distinguish their plasm by
taste, and may cause a deadly infection.

We have a particularly interesting and important species of chemical
irritation in the mutual attraction of the two sex-cells, to which
I gave the name of chemotropism thirty years ago, and which I
described as the earliest phylogenetic source of sexual love (see the
_Anthropogeny_, chapters vii. and xxix.). The remarkable phenomena
of impregnation, the most important of all the processes of sexual
generation, consist in the coalescence of the female ovum and the
male sperm-cell. This could not take place if the two cells had not a
sensation of their respective chemical constitution and disposition
for union; they come together under this impulse. This sexual affinity
is found at the lowest stages of plant life, in the protophyta and
algæ. With these both cells--the smaller male microgameta and the
larger female macrogameta--are often mobile, and swim about in order
to effect a union. In the higher plants and animals only the small
male cell is mobile as a rule, and swims towards the large immobile
ovum in order to blend with it. The sensation that impels it is of a
chemical nature, allied to taste and smell. This has been proved by
the splendid experiments of Pfeffer, who showed that the male ciliated
cells of ferns are attracted by malic acid, and those of the mosses by
cane-sugar, just in the same way as by the exhalation from the female
ovum. Conception depends on exactly the same erotic chemotropism in the
fertilization of all the higher organisms.

Erotic chemotropism must be regarded as a general sense-function of the
sexual cells in all amphigonous organisms, but in the higher organisms
special forms of the sex-sense, connected with specific organs, are
developed; as the source of sexual love they play a most important
part in the life of many of the histona. In man and most of the higher
animals these feelings of love are associated with the highest features
of psychic life, and have led to the formation of some most remarkable
customs, instincts, and passions. Wilhelm Bölsche has given us an
admirable selection from this infinitely rich and attractive realm
in his famous _Life of Love in Nature_ (1903). It is well known that
this sexual sense as we have it in man has been developed from the
nearest related mammals, the apes. But while it offers a shameless and
repulsive spectacle in many of the apes, it has been greatly ennobled
and refined in man in the development of civilization. However, the
sexual sense-organs and their specific energy have remained the same.
In the vertebrates and the articulates and many other metazoa the
copulative organs are equipped with special cell-forms (voluptuous
particles), which are the seat of intensely pleasurable feelings (see
the _Anthropogeny_, chapter xxix., plate 30). The pubic hairs which
clothe the _mons Veneris_ are also delicate organs of the sex-sense,
and so are the tactile hairs about the mouth. In these cases the
correlation between the sensitive forms of energy in the copulative
organs and the psychic functions of the central nervous system has
been remarkably developed. Moreover, a large part of the rest of the
skin may co-operate as a secondary organ of the sex-sense, as is seen
in the effect of caressing, stroking, embracing, kissing, etc. Goethe,
at once the greatest lyric poet and the subtlest and profoundest
monistic philosopher of Germany, has given unrivalled expression to
this sensual, yet supersensual, basis of sexual love. Ontogeny teaches
unmistakably that its elementary organs, the epidermic cells, develop
entirely from the ectoderm.

By "organic sensations" modern physiology understands the perception
of certain internal bodily states, which are mostly brought about by
chemical stimuli (to a small extent by mechanical and other irritation)
in the organs themselves. As subjective feelings of the organism itself
these states are most aptly called "feelings"--the positive states,
pleasure, comfort, delight; the negative, discomfort, pain, etc.
These organic sensations (also called common sensations or feelings)
are of great importance for the self-regulation of the complicated
organism. To the positive organic sensations belong not only the bodily
feeling of satiety, repose, or comfort, but also the psychic feelings
of joy, good humor, mental rest, etc. Among negative common feelings
we have not only hunger and thirst, bodily fatigue, bodily pain,
sea-sickness, etc., but also mental strain, vertigo, bad humor, and
so on. Between the two groups we have the third category of neutral
organic sensations, which involve neither pleasure nor pain, but merely
the perception of certain internal conditions, such as muscular strain
(in lifting heavy objects), the disposal of the limbs (in crossing the
legs), and so on.

Chemical sensation is just as general and important in organic nature
as in the life of organisms. In this case it is nothing less than the
basis of chemical affinity. No chemical process can be thoroughly
understood unless we attribute a mutual sensation to the atoms,
and explain their combination as due to a feeling of pleasure and
their separation to a feeling of displeasure. The great Empedocles
(fifth century B.C.) explained the origin of all things long ago by
the various combination of pure elements, the interaction of love
(attraction) and hate (repulsion). This attraction or repulsion is, of
course, unconscious, just as in the instincts of plants and animals. If
one prefers to avoid the term "sensation," it may be called "feeling"
(_æsthesis_), while the (involuntary) movement it provokes may be
called "inclination" (_tropesis_), and the capacity for the latter
"tropism" (more recently _taxis_, _cf._ chapter xii. of the _Riddle_).
We may illustrate it from the simplest case of chemical combination.
When we rub together sulphur and mercury, two totally different
elements, the atoms of the finely divided matter combine and form a
third and different chemical body, cinnabar. How would this simple
synthesis be possible unless the two elements _feel_ each other, move
towards each other, and _then_ unite?

We find universally distributed in nature the sensation of the
mechanical stimulus of gravitation, the most comprehensive statement
of which is given in Newton's law of gravity. According to this
fundamental and all-ruling law, any two particles of matter are
attracted in direct proportion to their mass and inverse proportion to
the square of their distance. This form of attraction, also, can be
traced to a "sensation of matter" in the mutually attracting atoms.
The local sensation that any body provokes by contact with the surface
of an organism is felt as pressure (_baros_). A stimulus that causes
this pressure alone brings about a counter-pressure as a reaction,
and an effort to neutralize it, the pressure-movement (_barotaxis_
or _barotropism_). Sensitiveness to pressure or the contact of solid
bodies is found throughout the organic world; it can be proved
experimentally among the protists as well as the histona. Special
sense-organs have been developed in the skin of the higher animals as
the instruments of this pressure-sense (baræsthesis) in the form of
tactile corpuscles; they are most numerous at the finger-tips and other
particularly sensitive parts. In many of the higher animals there is
a fine sense of touch in the feelers or tentacles, or (in the higher
articulates) in the horns or antennæ. Moreover, these tactile and
prehensile organs are also very widely found among the higher plants,
especially the climbing plants (vines, bryony, etc.). Their slender
creepers, which roll out spirally, have a very delicate feeling
for the nature of the supports which they embrace; they distinguish
between smooth and rough, thick and thin supports, and prefer the
latter. Many of the higher plants, which are particularly sensitive to
pressure, have, to an extent, special organs of touch (tentacles), and
reveal this by the movements of their leaves (the sensitive plants,
_mimosa_, _dionæa_, _oxalis_). But even among the unicellular protists
we find that the contact of solid bodies has an irritating effect, the
perception of which provokes corresponding movements (_thigmotaxis_ or
_thigmotropismus_). A peculiar form of pressure-sensation is produced
in many organisms by the flow of liquids; in the mycetozoa, for
instance, it provokes counter-movements (_rheotaxis_, _rheotropismus_),
as Ernst Strahl showed by his experiments on _æthelium septicum_.

We have an interesting analogy to the thigmotaxis of the viscous living
plasm in the elasticity of solid inorganic bodies, such as an elastic
steel-rod. In virtue of its springy nature, the elastic rod reacts
on the pressure of force that has bent it, and endeavors to regain
its former position. The spiral spring sets the works of the clock in
motion in virtue of its elasticity.

A very important part is played in botany by the action of gravitation
on the growth of plants. The attraction towards the centre of the earth
causes the positively geotropic roots to grow vertically into the
earth, while the negatively geotropic stalk pushes out in the opposite
direction. This applies also to a number of stationary animals which
are attached to the ground by roots, such as polyps, corals, bryozoa,
etc. And even the locomotion of free animals, the disposition of
their bodies to the ground, the position and posture of their limbs,
etc., is determined partly by the feeling of gravitation, and partly
by adaptation to certain functions which resist this, as in running,
swimming, and so on. All these geotropic sensations belong to the
same group of barotactile phenomena, as the fall of a stone or any
other effect of gravitation that depends on an inorganic feeling of
attraction.

As a result of these adaptations, we find a distinct sense of space
developed in the higher, free-moving animals. The feeling of the three
dimensions of space becomes an important means of orientation, and in
the vertebrates, from the fishes up to man, the three spiral canals
in the inner ear are developed as special organs of this. These three
semicircular canals, which lie vertically to each other in the three
dimensions of space, are the organs of the sensation that guides the
movements of the head, and, in relation to this, for the normal posture
of the body and the feeling of equilibrium. If the three spiral canals
are destroyed, the equilibrium is lost; the body totters and falls.
Hence, these organs are not of an acoustic, but a static or geotactic
character; and the same may be said of the so-called "auditory
vesicles" of many of the lower animals--round vesicles which contain
a liquid and a solid body, the otolith. When this body changes its
position with the change of posture of the whole frame, it presses on
the fine auditory hairs, or delicate terminations of the auscultory
nerve, which enters the vesicle. In fact, the sense of equilibrium is
often combined with the sense of hearing.

The perception of noises and tones, which we call hearing, is
restricted to a section of the higher, free-moving animals; if, that is
to say, the above-mentioned "auditory vesicles" in the lower animals
do not have acoustic as well as static sensations. The specific
sensation of hearing is due to vibration of the medium in which the
animal lives (air or water), or to vibrations of solid bodies (such as
tuning-forks) which are brought into touch with them. If the vibrations
are irregular, they are felt as "noises"; if regular, they are heard
as "tones" or notes; when a number of tones together (fundamental
and over-tones) excite a complex sensation, we have "timbre." The
vibrations of the sounding body are borne to the auditory cells, which
represent the terminal extensions of the auscultory nerve. The specific
sensation of hearing can, therefore, be traced originally to the sense
of pressure, from which it has been evolved. As the organ of hearing
is, like the eye, one of the principal instruments of the higher mental
life, and as the refined musical hearing of civilized man is often
taken to be a metaphysical power of the soul, it is important to note
that here again the starting-point was purely physical--that is to say,
it can be traced to the sense of pressure of matter, or gravitation.

The great importance of electricity as an agency in nature, both
organic and inorganic, has only lately been fully appreciated. Electric
changes are connected with many (if not, as is now supposed, with
all) chemical and optical processes. Man himself and most of the
higher animals have no electric organs (apart from the eye), and no
sense-organs that experience a specific electric sensation. It is
probably otherwise with many of the lower animals, especially those
that develop free electricity, such as the electric fishes. The larvæ
of frogs and embryos of fishes, if put in a vessel of water through
which a galvanic current is sent, place themselves when it is closed
with their longitudinal axis in the direction of the current, with
the head directed to the anode and the tail to the cathode (Hermann).
Again, the luminous sea-animals which cause the beautiful phenomenon
of the illumination of the sea, and the glow-worms and other luminous
organisms, have probably an unconscious feeling of the flow of electric
energy associated with these phenomena. Many plants show a direct
reaction to electric stimuli; when, for instance, we send a constant
galvanic current for some time through the points of their roots (very
sensitive organs, compared by Darwin to the brain of the animal), they
bend towards the cathode.

Many of the protists are very sensitive to electric currents, as Max
Verworn especially proved by a series of beautiful experiments. Most
of the ciliated infusoria and many of the rhizopods (_amœba_) are
cathodically sensitive or negatively galvanotactic. When we send a
constant electric current through a drop of water in which thousands of
_paramœcium_ are moving about, all the infusoria swim at once, with
the anterior pole of the body foremost, towards the cathode or negative
pole; they accumulate about it in great crowds. If the direction of the
current is now changed, the whole swarm at once make in the opposite
direction for the new cathode. Most of the flagellate infusoria do just
the reverse; they are anodically sensitive or positively galvanotactic.
In a drop of water, in which swarms of _polytoma_ are moving about,
all the cells swim at once towards the anode or positive pole, when an
electric current is sent through. The opposite galvanotropic behavior
of these two groups of infusoria in a drop of water, in which they
are mixed together, is very interesting; as soon as a constant stream
enters it, the ciliata fly to the cathode and the flagellata to the
anode. When the current is reversed the two swarms rush at each other
like hostile armies, cross in the middle of the drop, and gather at the
opposite poles. These and other phenomena of galvanic sensation show
clearly that the living plasm is subject to the same physical laws as
the water that is decomposed into hydrogen and oxygen by an electric
current. Both elements _feel_ the opposite electricities.


SCALE OF SENSATION AND IRRITABILITY

 1st Stage: SENSATION OF ATOMS. Affinity of the elements in every
 chemical combination.

 2d Stage: SENSATION OF MOLECULES (groups of atoms): in the attraction
 and repulsion of molecules (positive and negative electricity, etc.).

 3d Stage: SENSATION OF PLASTIDULES (micella, biogens, or
 plasma-molecules): in the simplest vital process of the monera
 (chromacea and bacteria).

 4th Stage: SENSATION OF CELLS: irritability of the unicellular
 protists (protophyta and protozoa): erotic chemotropism connected
 with the nucleus and trophic with the cell-body.

 5th Stage: SENSATION OF CŒNOBIA (volvox, magosphæra). With the
 formation of cell-communities we have association of sensations
 (individual feeling on the part of the social cells together with
 common feeling on the part of the community).

 6th Stage: SENSATION OF THE LOWER PLANTS. In the metaphyta or
 tissue-plants all the cells are still equally sensitive at the lower
 stages: there are no special sense-organs.

 7th Stage: SENSATION OF THE HIGHER PLANTS. In the higher metaphyta
 specially sensitive cells, or groups of cells, with a specific
 energy, are developed at certain points: sense-organs.

 8th Stage: SENSATION OF THE LOWER METAZOA, without differentiated
 nerves or sense-organs. Lower cœlenteria: sponges, polyps,
 platodaria.

 9th Stage: SENSATION OF THE HIGHER METAZOA, with differentiated
 nerves and sense-organs, but still without consciousness(?). The
 higher cœlenteria and most of the cœlomaria.

 10th Stage: SENSATION WITH DAWNING CONSCIOUSNESS, with independent
 formation of the phronema. The higher articulata (spiders and
 insects) and vertebrates (amphibia, lower reptiles, lower mammals).

 11th Stage: SENSATION WITH CONSCIOUSNESS AND THOUGHT: amniotes:
 higher reptiles, birds, and mammals: savages.

 12th Stage: SENSATION WITH PRODUCTIVE MENTAL ACTION IN ART AND
 SCIENCE: civilized men.




XIV

MENTAL LIFE

 Mind and soul--Intelligence and reason--Pure reason--Kant's
 dualism--Anthropology--Anthropogeny--Embryology of the mind--Mind of
 the embryo--The canonical mind--Legal rights of the embryo--Phylogeny
 of the mind--Paleontology of the mind--Psyche and phronema--Mental
 energy--Diseases of the mind--Mental powers--Conscious and
 unconscious mental life--Monistic and dualistic theory--Mental life
 of the mammals, of savages, and of civilized and educated people.


The greatest and most commanding of all the wonders of life is
unquestionably the mind of man. That function of the human organism,
to which we give the name of "mind," is not only the chief source of
all the higher enjoyment of life for ourselves, but it is also the
power that most effectually separates man from the brute according
to conventional beliefs. Hence it is supremely important for our
biological philosophy to devote a few careful pages to the study of its
nature, its origin and development, and its relation to the body.

At the very outset of our psychological inquiry we are met by the
difficulty of giving a clear definition of "mind," and distinguishing
it from "soul." Both ideas are extremely ambiguous: their content
and connotation are described in the most various ways by the
representatives of science. Generally speaking, we mean by mind that
part of the life of the soul which is connected with consciousness and
thought, and is, therefore, only found in the higher animals which have
intelligence and reason. In a narrower sense reason is regarded as the
proper function of mind, and as the essential prerogative of man in the
animal world. In this sense Kant especially has done much to strengthen
the prevailing conception of mental action, and has, by his _Critique
of Pure Reason_, converted philosophy into a mere "science of reason."
In consequence of this conception, which still prevails widely in
scientific circles, we will first study the mental life in the action
of reason, and try to form a clear idea of this great wonder of life.

Psychologists and metaphysicians are of very varied opinions as to
the difference between intelligence and reason. Schopenhauer, for
instance, considers causality to be the sole function of intelligence,
and the formation of concepts to be the province of reason; in his
opinion the latter power alone marks off man from the brute. However,
the power of abstraction, which collects the common features in a
number of different presentations, is also found in the higher animals.
Intelligent dogs not only discriminate between individual men, cats,
etc., according as they are sympathetic or the reverse, but they have
a general idea of man or cat, and behave very differently towards the
two. On the other hand, the power of forming concepts is still so
slight in uncivilized races that it rises but little above the mind of
dogs, horses, etc.; the mental interval between them and civilized man
is extremely wide. However, a long scale of reason unites the various
stages of association of presentations which lead up to the formation
of concepts; it is quite impossible to lay down a strict line of
demarcation between the lower and higher mental functions of animals,
or between the latter and reason. Hence the distinction between the
two cerebral functions is only relative; the intelligence comprises
the narrower circle of concrete and more proximate associations, while
reason deals with the wider sphere of abstract and more comprehensive
groups of association. In the scientific life of the mind, therefore,
the intelligence is always occupied with empirical investigation, and
reason with speculative knowledge. But the two faculties are equally
functions of the phronema, and depend on the normal anatomic and
chemical condition of this organ of thought.

Since Kant won so great a prominence in modern philosophy for the
idea of pure reason by his famous _Critique_ (1781), it has been much
discussed, especially in the modern metaphysical theory of knowledge.
It has, however, like all other ideas, undergone considerable changes
of meaning in the course of time. Kant himself at first understood
by pure reason "reason independent of all experience." But impartial
modern psychology based on the physiology of the brain and the
phylogeny of its functions, has shown that there is no such thing as
this pure _a priori_ knowledge, independent of all experience. Those
principles of reason which at present seem to be a priori in this sense
have been attained in virtue of thousands of experiences. In so far as
this is a question of real knowledge of the truth, Kant himself has
frequently recognized the point. He says expressly in his _Prolegomena
to any future metaphysic that can be regarded as Science_ (1783, p.
204): "A knowledge of things by pure reason or pure intelligence is
nothing but an empty appearance; only in experience is there truth."
In subscribing to this empirical theory of knowledge of Kant I. and
rejecting the transcendental theory of Kant II., we may on our side
understand by pure reason "knowledge without prejudices," free from all
dogma--all fictions of faith.

The familiar cry of modern metaphysicians, "Return to Kant," has become
so general in Germany that not only nearly all metaphysicians--the
official representatives of "philosophy" at our universities--but
also many distinguished scientists, regard Kant's dualistic theory of
knowledge as a necessary condition for the attainment of truth. Kant
dominated philosophy in the nineteenth century much as Aristotle did
in the Middle Ages. His authority became especially powerful when the
prevailing Christian faith believed that his "practical reason" fully
supported its own three fundamental dogmas--the personality of God, the
immortality of the soul, and the freedom of the will. It overlooked
the fact that Kant had utterly failed to find proofs of these dogmas
in his _Critique of Pure Reason_. Even conservative governments found
favorable features in this dualistic philosophy. We are, therefore,
forced to return once more to this mischievous system; though Kant's
antinomy of the two reasons has now been refuted so often and so
thoroughly that we need not dwell any further on this point.

Although the great Königsberg philosopher brought every side of
human life within his comprehensive sphere of study, man remained to
him--as he had been to Plato and Aristotle, Christ and Descartes--a
dual being, made up of a physical body and a transcendental mind or
spirit. Comparative anatomy and evolution, which have provided the
solid morphological basis of monistic anthropology, did not come
into existence until the beginning of the nineteenth century; they
were quite unknown to Kant. He had, however, a presentiment of their
importance, as Fritz Schultze has shown in his interesting work on
_Kant and Darwin_ (1875). We find in various places expressions which
may be described as anticipations of Darwinism. Kant also gave lectures
on "Pragmatic Anthropology," and studied the psychology of races and
peoples. It is remarkable that he did not arrive at a phylogenetic
conception of the human mind, and a recognition of the possibility of
its evolution from the mind of other vertebrates. It is clear that he
was held back from this by the profound mystic tendency of his theory
of reason, and the dogma of the immortality of the soul, the freedom
of the will, and the categorical imperative. Reason remained in Kant's
view a transcendental phenomenon, and this dualistic error had a
great influence on the whole structure of his philosophy. It must be
remembered, of course, that our knowledge of the psychology of peoples
was then very imperfect; but a critical study of the facts then known
should have sufficed to convince him of the lower and animal condition
of their minds. If Kant had had children, and followed patiently the
development of the child's soul (as Preyer did a century later), he
would hardly have persisted in his erroneous idea that reason, with
its power of attaining _a priori_ knowledge, is a transcendental and
supernatural wonder of life, or a unique gift to man from Heaven.

The root of the error is that Kant had no idea of the natural
evolution of the mind. He did not employ the comparative and genetic
methods to which we owe the chief scientific achievements of the last
half-century. Kant and his followers, who confined themselves almost
exclusively to the introspective method or the self-observation of
their own mind, regarded as the model of the human soul the highly
developed and versatile mind of the philosopher, and disregarded
altogether the lower stages of mental life which we find in the child
and the savage.

The immense advance made by the science of man in the second half
of the nineteenth century cut the ground from under the older
anthropology and the dualistic system of Kant. A number of newly
founded branches of science co-operated in the work. Comparative
anatomy showed that our whole complicated frame resembles that of
the other mammals, and in particular differs only by slight stages
of growth, and therefore in the details of the organs, from that
of the anthropoid apes. The comparative histology of the brain
especially showed that this is also true of the brain, the real organ
of mind. From comparative embryology we learned that man develops
from a simple ovum just like the anthropoid ape; in fact, that it is
almost impossible to distinguish between the ape and the human embryo
even at a late stage of development. Comparative animal chemistry
explained that the chemical compounds which build up our organs, and
the conversions of energy which accompany its metabolism, resemble
those in the other vertebrates. Comparative physiology taught us that
all man's vital functions--nutrition and reproduction, movement and
sensation--can be traced to the same physical laws in man as in all
the other vertebrates. Above all, the comparative and experimental
study of the sense-organs and the various parts of the brain showed
that these organs of the mind work in the same way in man as in the
other primates. Modern paleontology taught that man is, it is true,
more than a hundred thousand years old, but only appeared on earth
towards the close of the Tertiary Period. Prehistoric research and
comparative ethnology have shown that civilized nations were preceded
by older and lower races, and these by savages, which have a close
bodily and mental affinity to the apes. Finally, the reformed theory
of descent (1859) enabled us to unite the chief results of the various
branches of anthropological study, and explain them phylogenetically
by the development of man from other primates (anthropoid apes,
cynocephali, lemures, etc.). By this means a new and monistic basis
was provided for modern anthropology; the position assigned to man in
nature by dualistic metaphysics was shown to be utterly untenable. I
have attempted in the last edition of my _Anthropogeny_ (of which an
English edition is in preparation) to combine all these results of
empirical investigation in a sketch of the natural evolution of man,
paying special regard to embryology. I pointed out in chapters ii.-vi.
of the _Riddle_ how important a part of our monistic philosophy this
phylogenetic anthropology is.

The monistic conception of the human body and mind, which the theory
of descent has put on a zoological basis, was bound to meet with the
sternest resistance in dualistic and metaphysical circles. It was,
however, also regarded with great disapproval by many modern empirical
anthropologists, especially those who take it to be their chief
task to make as "exact" a study as possible of the human frame, and
measure and describe its various parts. We might have expected these
descriptive anthropologists and ethnologists to extend a friendly
hand to the new anthropogeny, and avail themselves of its leading
ideas, in order to bring unity and causal connection into the enormous
mass of empirical material accumulated. However, this took place
only to a limited extent, The majority of anthropologists regarded
evolution, and especially the evolution of man, as an undemonstrated
hypothesis. They confined themselves to accumulating huge masses of
raw empirical material, without having any clear aim or any definite
questions in view. This was chiefly the case in Germany, where the
Society of Anthropology and Prehistoric Research was for thirty years
under the lead of Rudolph Virchow. This famous scientist had won
great honor in connection with the reform of medicine by his cellular
pathology and a number of distinguished works on pathological anatomy
and histology since the middle of the nineteenth century. But when
he afterwards (subsequently to his removal to Berlin, 1856) devoted
himself chiefly to political and social questions, he lost sight of the
great advance made in other branches of biology. He completely failed
to appreciate its greatest achievement--the establishment of the
science of evolution by Darwin. To this we must add the psychological
metamorphosis (similar to that of Wundt, Baer, Dubois-Reymond, and
others), of which I have spoken in the sixth chapter of the _Riddle_.
The extraordinary authority of Virchow, and the indefatigable zeal
with which he struggled every year until his death (1903) against the
descent of man from other vertebrates, caused a wide-spread opposition
to the doctrine of evolution. This was supported especially by Johannes
Ranke, of Munich, the secretary of the Anthropological Society.
Happily, a change has recently set in. However, my _Anthropogeny_
has remained for thirty years the only work of its kind--namely, a
comprehensive treatment of man's ancestral history, especially in the
light of embryology.

As I pointed out in the eighth and ninth chapters of the _Riddle_, the
most solid foundation of our monistic psychology is the fact that the
human mind grows. Like every other function of our organism, our mental
activity exhibits the phenomenon of development in two directions,
individually in each human being and phyletically in the whole race.
The ontogeny of the mind--or the embryology of the human soul--brings
before us in direct observation the various stages of development
through which the mind of every man passes from the beginning to the
close of life. The phylogeny of the mind--or the ancestral history of
the human soul--does not afford us this direct observation; it can only
be deduced by a comparison and synthesis of the historical indications
which are supplied by history and prehistoric research on the one hand,
and the critical study of the various stages of mental life in savages
and the higher vertebrates on the other. In this the biogenetic law is
used with great success (chapter xvi.).

As everybody knows, the new-born child shows as yet no trace of mind
or reason or consciousness; these functions are wanting in it as
completely as in the embryo from which it has been developed during
the nine months in the mother's womb. Even in the ninth month, when
most of the organs of the human embryo are formed and arranged as they
appear later, there is no more trace of mind in its psychic life than
in the ovum and spermatozoon from which it was evolved. The moment in
which these sexual cells unite marks precisely the real commencement of
individual existence, and therefore of the soul also (as a potential
function of the plasm). But the mind proper--or reason, the higher
conscious function of the soul--only develops, slowly and gradually,
long after birth. As Flechsig has shown anatomically, the cortex in the
new-born child is not yet organized or capable of functioning. Rational
consciousness is even impossible for the child when it begins to speak;
it reveals itself for the first time (after the first year) at the
moment when the child speaks of itself, not in the-third person, but
as "I." With this self-consciousness comes also the antithesis of the
individual to the outer world, or world-consciousness. This is the real
beginning of mental life.

In defining the appearance of the individual mind by the awakening
of self-consciousness, we make it possible to distinguish, from the
monistic physiological point of view, between "soul" (_psyche_) and
"spirit" (_pneuma_). There is a soul even in the maternal ovum and
the paternal spermatozoon (_cf._ chapter xi.); there is an individual
soul in the stem-cell (_cytula_) which arises at conception by the
blending of the parent cells. But the mind proper, the thinking reason,
develops out of the animal intelligence (or earlier instincts) of the
child only with the consciousness of its personality as opposed to the
outer world. At the same time the child reaches the higher stage of
personality, which law has for a long time taken under its protection
and made morally responsible to society by education. This shows how
erroneous and untenable, from the physiological point of view, are the
ideas still embodied in our code as to the psychic life and the mind of
the embryo and the new-born infant. They came mostly from the canon law
of the Catholic Church.

The dualistic ideas of the soul of the human embryo which were taught
by the Church in the Middle Ages are particularly interesting from
the psychological point of view; and at the same time they are of
great practical importance even in our own day, since many of their
moral consequences form an important element in canon law, and have
passed from this into civil law. This influential canon law was formed
under ecclesiastical authority from the decisions of Church councils
and the decretals of the popes. It is, like most of the dogmas and
decrees which civilization owes to this powerful hierarchy, a curious
tissue of old traditions and new fictions, political dogmas, and
crass superstition. It is directed to the despotic ruling of the
uneducated masses and the exclusive dominion of the Church--a Church
that calls itself Christian while thus acting as the very reverse of
pure Christianity. The canon law takes its name from the dogmatic rules
(or canons) of the Church. They involuntarily suggest the metal tubes
which are so often the _ultima ratio regis_ in the wars of Christian
nations. The canonical regulations of the Church, as implements of a
crude spiritual despotism, have no more to do with the ethical laws
of pure reason than the cannons of secular authorities have as naked
organs of physical force. We might write the motto, _Ultima ratio
ecclesiæ_ (the last argument of the Church), over the sacred _Corpus
Juris Canonici_. A collection of later papal decretals which forms an
appendix to the books of canon law was very happily given the official
title of _Extravagantes_. Among the "extravagant" nonsense which the
papacy included in canon law as a moral code for believers is its view
of the psychic life of the embryo. The "immortal soul" is supposed
to enter the soulless embryo only several weeks after conception. As
theologians and metaphysicians are very much divided as to the period
of this entrance of the soul, and know nothing about the structure of
the embryo and its development, we will only recall the fact that the
human fœtus cannot be distinguished from that of the anthropoid
ape and other mammals even in the sixth week of its development. The
outline of the five cerebral vesicles and the three higher sense-organs
(nose, eye, and ear vesicle) is discernible in the head; the two
pairs of limbs can be traced in the shape of four simple roundish
unjointed plates; and the pointed tail sticks out at the lower part,
the rudimentary legacy from our long-tailed ape-ancestors. Although the
cortex is not yet developed at this stage, the embryo may be considered
to have a "soul" (_cf._ chapters xiv. and xv. of my _Anthropogeny_, and
plates 8-14).

It is said to be a great merit of canon law that it was the first to
extend legal protection to the human embryo, and punished abortion
with death as a mortal sin. But as this mystical theory of the
entrance of the soul is now scientifically untenable, we should expect
them consistently to extend this protection to the fœtus in its
earlier stages, if not to the ovum itself. The ovary of a mature maid
contains about 70,000 ova; each of these might be developed into a
human being under favorable circumstances if it united with a male
spermium after its release from the ovary. If the state is so eager
for the multiplication of its citizens in the general interest, and
regards prolific reproduction as a "duty" of its members, this is
certainly a "sin of omission." It punishes abortion with several
years' imprisonment. But while civil law thus takes its inspiration
from canon law, it overlooks the physiological fact that the ovum is
a part of the mother's body over which she has full right of control;
and that the embryo that develops from it, as well as the new-born
child, is quite unconscious, or is a purely "reflex machine," like
any other vertebrate. There is no mind in it as yet; it only appears
after the first year, when its organ, the phronema in the cortex, is
differentiated. This interesting fact is explained by the biogenetic
law, which shows that the ontogeny of the brain is a condensed
recapitulation of its phylogeny in virtue of the laws of heredity.

The biogenetic law applies just as much to the brain, the organ of
mind, as to any other organ of the human body. On the strength of the
ontogenetic facts, which fall under direct observation, we infer that
there was a corresponding development in the phylogenetic series of
our animal ancestors. A significant confirmation of this inference is
found in comparative anatomy. It shows that in all the skull-animals
(_craniota_)--from the fishes and amphibia up to the apes and man--the
brain is developed in the same way, as a vesicular distension of
the ectodermal medullary tube. This simple oval cerebral vesicle
first divides into three and afterwards five successive vesicles by
transverse constriction (_Anthropogeny_, chapter xxiv., plate 24). It
is the first of these vesicles, the cerebrum, that afterwards becomes
the chemical laboratory of the mind. In the lower craniota (fishes and
amphibia) the cerebrum remains very small and simple. It only reaches
a notably higher stage in the three chief classes of the vertebrates,
the amniotes. As these land-dwelling and air-breathing craniota have
more difficult work to do in the struggle for life than their lower
aquatic ancestors, we find much more varied and complex habits among
them. These hereditary habits are gradually converted into instincts by
functional adaptation and progressive heredity; and with the further
development of consciousness in the higher mammals we have at last
the appearance of reason. The gradual unfolding of the mental life is
accompanied step by step with the advance of its anatomic organ, the
phronema in the cortex. Recent careful investigations of the ontogeny
and histology of the origin of mind (by Flechsig, Hitzig, Edinger,
Ziehen, Oscar Vogt, etc.) have given us an interesting insight into the
mysterious processes of its phylogeny.

While the comparative anatomy of the cortex gives us a good idea
of the gradual historical development of the mind in the higher
classes of vertebrates, we get at the same time from their fossilized
remains positive indications as to the period of time in which this
phylogenesis has slowly taken place. The historical series in which the
classes of vertebrates have succeeded each other in the great periods
of the organic history of the earth is directly demonstrated by their
fossil remains--the real commemorative medals of natural creation--and
gives us a most valuable record of the ancestral history of our race
and of the mind. The oldest strata that contain vertebrate remains
form the huge Silurian System, which were, on the latest calculations,
formed more than a hundred million years ago. They contain a few fossil
fishes. In the succeeding Devonian System these are followed by the
dipneusta, transitional forms between the fishes and the amphibia. The
latter, the oldest four-footed and five-toed vertebrates, appear in
the Carboniferous Period. They are succeeded in the Permian, the next
system, by the oldest amniotes, the primitive reptiles (tocosauria).
It is not until the next period (the Triassic) that the oldest mammals
are found, small primitive monotremes (_pantotheria_), then marsupials
in the Jurassic, and the first placentals in the Cretaceans. The great
wealth of varied and highly organized forms which are contained in this
third and last sub-class of the mammals appear only in the succeeding
Tertiary Period. The numbers of well-preserved skulls which these
placentals have left behind in fossil form are particularly important,
because they give us an idea of the quantitative and qualitative
formation of the brain within the various orders; thus, for instance,
in the modern carnivora the brain is from two to four times, and in the
modern ungulates from six to eight times, as large (in proportion to
the size of the body) as in their earliest Tertiary ancestors. It is
also found that the cortex (the real organ of mind) has developed in
the Tertiary Period at the expense of the other parts of the brain. The
duration of this Cænozoic Period has lately been calculated at three
million years (according to other geologists twelve to fourteen or more
million years). It was, at all events, sufficient to make possible the
gradual development of the human mind from the lower intelligence of
our ape-ancestors and the instincts of the older placentalia.

We have given the physiological name of the "phronema," as the real
organ of mind or the instrument of reason, to that part of the cortex
on the normal anatomic condition of which the action of the human mind
depends. The remarkable investigations during the last few decades of
the finer texture of the grey cortex (or cortical substance of the
cerebrum) have shown that its structure--a real anatomic "wonder of
life"--represents the most perfect morphological product of plasm;
and its physiological function--mind--is the most perfect action of
a "dynamo-machine," the highest achievement that we know anywhere
in nature. Millions of psychic cells or neurona--each of them of an
extremely elaborate fibril molecular structure--are associated as
special thought-organs (phroneta) at certain parts of the cortex, and
these again are built up into a large harmonious system of wonderful
regularity and capacity. Each phronetal cell is a small chemical
laboratory, contributing its share to the unified central function of
the mind, the conscious action of reason. Scientists are still very far
from agreement as to the extent of the phronema in the cortex and its
delimitation from the neighboring sense-centres (sensoria). But they
are all agreed that there is such a central organ of mind, and that its
normal anatomic and chemical condition is the first requisite for the
life of the human mind. This belief--one of the foundations of monistic
psychology--is confirmed by the study of psychiatry.

The study of the diseased organism has greatly furthered our knowledge
of the normal frame. Diseases are so many physiological experiments
made by nature herself under special conditions, which experimental
physiology would often be unable to arrange artificially. The
thoughtful physician or pathologist can often obtain most important
knowledge of the function of organs by carefully observing them during
disease. This is especially true of diseases of the mind, which
always have their immediate foundation in an anatomical or chemical
modification of certain parts of the brain. Our advancing knowledge
of the localization of mental functions, or of their connection with
special phroneta or organs of thought, is for the most part based on
the experience that the destruction of the one is followed by the
extinction of the other. Modern psychiatry, the empirical science of
mental disease, has thus become an important element of our monistic
psychology. If Immanuel Kant had studied it and had visited the
asylum wards for a few months, he would certainly have escaped the
dualist errors of his philosophy. We may say the same of the modern
metaphysical psychologists who built up a mystic theory of an immortal
soul without knowing the anatomy, physiology, and pathology of the
brain.

The comparative anatomy, physiology, and pathology of the brain, in
concurrence with the results of ontogeny and phylogeny, have led
us to form the sound monistic principle that the human mind is a
function of the phronema, and that the neurona of the latter, or the
phronetal cells, are the real elementary organs of mental life. Hence
modern energism is perfectly justified in regarding mental energy
(in all its forms) from the same point of view as all other forms of
nervous energy, and in fact all manifestations of energy in organic
or inorganic nature. Fechner's psychophysics had already shown that a
part of this nervous energy is measurable and mathematically reducible
to the mechanical laws of physics (_Riddle_, chapter vi.) Ostwald
has, in his _Natural Philosophy_, lately emphasized the fact that all
the manifestations of mental life, not only sensation and will, but
even thought and consciousness, can be reduced to nervous energy.
Hence we may distinguish what are called mental forces from the other
expressions of nervous energy as _phronetic energy_. The monistic
research of Ostwald on the energy-processes in mental life (chapter
xviii.), consciousness (chapter xix.), and will (chapter xx.) is very
notable, and confirms the views I advanced in the second part of the
_Riddle_ (chapters vi., x., and xi.). Ostwald has, however, caused
some misunderstanding by insisting on substituting his idea of energy
for the pure notion of substance (as Spinoza had formulated it), and
by rejecting the other attribute of substance, matter. His supposed
"Refutation of Materialism" is a mere attack on windmills; his energism
(the consistent dynamism of Leibnitz, etc.) is just as one-sided as its
apparent opposite, the consistent materialism of Democritus, Holbach,
etc. The latter makes matter precede force; the former regards matter
as the product of force. Monism escapes the one-sidedness of both
systems, and, as hylozoism, refuses to separate the two attributes of
substance, space-filling matter and active energy. This applies to
mental life just as to any other natural process; our mental forces or
phronetic energies are just as much bound up with the neuroplasm, the
living plasm of the neurona in the cortex, as the mechanical energy
of our muscles is with the contractile myoplasm, the living muscular
substance.

In the exhaustive study of consciousness which I gave in the tenth
chapter of the _Riddle_ I sought to show that this enigmatic
function--the central mystery of psychology--is not a transcendental
problem, but a natural phenomenon, subject to the law of substance,
as much as any other psychic power. The child's consciousness only
develops long after its first year, and grows as gradually as any other
psychic function; like these, it is bound up with the normal anatomic
and chemical condition of its organs, the phroneta in the cortex.
Consciousness develops originally out of unconscious functions (as an
"inner view," or mirroring, of the action of the phronema); and at any
time an unconscious process in the cortex may come within the sphere
of consciousness by having the attention directed to it. On the other
hand, conscious actions, which need a good deal of attention when they
are first learned (such as playing the piano), may become unconscious
through frequent repetition and practice. The fact that chemical energy
is converted in the phronetal cells during any of these actions is
proved by the fatigue and exhaustion which prolonged mental work causes
in the brain, just as mechanical work does in the muscles. Fresh matter
has to be supplied by the food before the mental work can be continued.
Moreover, it is well known that various drinks have a considerable
influence on consciousness (coffee and tea, beer and wine); and the
temporary extinction of it under chloroform or ether is an analogous
fact. Again, the familiar phenomena of the dream, the deviations from
normal consciousness, hallucinations, delusions, etc., must convince
every impartial thinker that these mental functions are not of a
metaphysical character, but physical processes in the neuroplasm of the
brain, and thoroughly dependent on the law of substance.

In complete contrast to this natural monistic conception of the
human mind, which is, in my opinion, definitely established by
nineteenth-century science, we have the older dualistic estimate of
it which is still widely accepted both by unlearned and learned,
especially metaphysicians and theologians. I have already dealt in
the _Riddle_ (chapter xi.) with the grounds for this belief in an
immaterial soul, and expressed my conviction that "the belief in the
immortality of the human soul is in flagrant contradiction to the
soundest empirical principles of modern science." I must refer the
reader to what I said there about thanatism and athanatism, only
reminding him once more of the immense influence of the Kantist
philosophy in maintaining this belief in the spirituality of the
soul. Kant derived from the introspective study of his own gifted
mind an extremely high estimate of human reason, and he fallaciously
transferred this estimate to the human mind generally. He did not
perceive that it is either wholly wanting in the savage, or does not
rise much above the stage which has been reached by the intelligence of
the dog, horse, elephant, and other advanced animals.

Modern anthropogeny has raised the theory of evolution to the rank of
an historical fact. All the various organs of our body resemble those
of our nearest relatives, the anthropoid apes, in their structure and
composition. They only differ from them in details of form and size,
which are determined by inherited variations of growth. But the
functions as well as the organs have been inherited by man from his
primate ancestors. This applies to the mind also, which is merely the
collective function of the phronema, the central organ of thought.
An impartial comparison of mental life in the anthropoid ape and
the savage shows that the differences between the two are not more
considerable than the differences in the structure of their brains.
Hence, if one accepts the dualistic theory of the soul formulated by
Plato and Kant and accepted by so many modern psychologists, it is
necessary to attribute an immortal soul to the anthropoid apes and the
higher mammals (especially to domestic dogs) just as well as to savage
or civilized man (_cf._ chapter xi. of the _Riddle_).

The thorough and careful study of the mental life of the savage,
supported by the results of anthropogeny and ethnography, has in the
course of the last forty years decided the issue of this struggle
between the conflicting theories of the origin of civilization. The
older theory of degeneration, based on religious beliefs, and so
preferred by theologians and theosophists, declared that man--the
"image of God"--was created originally with perfect bodily and mental
powers, and only fell away from his high estate after the original
sin. On this view the present savages are degenerate descendants of
the first godlike men. (In tropical lands the anthropoid apes are in
similar fashion regarded by the natives as degenerate branches of
their own stem!) Although this Biblical degeneration theory is still
taught in most of our schools, and even supported by a few mystic
philosophers, it had lost all scientific countenance before the end
of the nineteenth century. It is now replaced by the modern theory
of evolution, which was represented by Lamarck, Goethe, and Herder
a century ago, and raised to a predominant position in ethnography
by Darwin and Lubbock. It has taught us that human civilization is
the outcome of a long and gradual process of evolution, covering
thousands of years. The civilized races of our time have arisen from
less civilized races, and these in turn from lower, until we reach the
savage races which show no trace of civilization.

Ethnologists distinguish as a separate class the races which are found
midway between the civilized peoples and the savages. We shall deal
with their classification and characteristics later on (chapter xvii.).
These races show some advance on the artistic instinct which we find in
a slight degree even among the savages at times; moreover, their animal
curiosity develops into human curiosity, and raises the question of the
causes of phenomena, the germ of all science.

Civilized races, which occupy the next stage to these, are raised above
them by the formation of larger states and a greater division of labor.
The specialization of the various groups of workers and the greater
ease of maintenance permit a further development of art and science. To
these groups belong, of living races, the majority of the Mongolians,
and the greater part of the inhabitants of Europe and Asia in ancient
and mediæval times. The great ancient civilizations of China, Southern
India, Asia Minor, Egypt, and afterwards of Greece and Italy, show not
only a great development of art and science, but also a concern for
legislation, religious worship, education of the young, and the spread
of knowledge by written books.

Civilization in the narrower sense, characterized by a high development
of art and science and the manifold application of them to practical
life in legislation, education, etc., was greatly advanced even in
antiquity among several nations--in Asia by the Chinese, Southern
Indians, Babylonians, and Egyptians; in Europe by the Greeks and Romans
of the classic age. However, their results were at first restricted
to narrow fields, and were mostly lost during the Middle Ages. Modern
civilization rose to importance about the end of the fifteenth century,
when the invention of printing had made possible the spread of
knowledge far and wide, the discovery of America and circumnavigation
of the globe had widened the horizon, and the Copernican system had
demolished the error of geocentricism. Then began the many-sided
growth of civilization which has reached so marvellous a height in the
nineteenth century through the extraordinary development of science.
Then at last free reason could triumph over the prevailing mediæval
superstition.




XV

THE ORIGIN OF LIFE


 The miracle of the origin of life--Creation of species: Moses and
 Agassiz--Creation of the first cells: Wigand and Reinke--Agnostic
 position: resignation--Eternity hypothesis (dualistic, Helmholtz;
 monistic, Preyer)--Archigony hypothesis (autogony hypothesis,
 Haeckel, Nägeli; cyanic hypothesis, Pflüger, Verworn)--Spontaneous
 generation--Saprobiosis or necrobiosis--Experiments in spontaneous
 generation--Pasteur--Stages of archigony--Observation of
 archigony--Synthesis of plasma--Value of the unsuccessful experiments
 to produce plasm artificially--The logic of modern experimental
 biology.


The question of the origin of life is one of the most important and
interesting, but one of the most difficult and complicated, problems
with which the mind of man has been occupied for thousands of years.
There are few other questions (such as the freedom of the will or
personal immortality) on which such different and contradictory views
have been expressed, and few that remain so far from being closed
at the present day. There are, moreover, few problems on which the
opinions of even distinguished thinkers diverge so much, and have
degenerated so much into fantastic hypotheses. This is partly due to
the extreme difficulty of giving a strictly scientific solution of
the problem and partly to the confusion of ideas which is so great in
this controversy, the lack of clear rational insight, and the powerful
authority of the prevailing religious faith and other venerable dogmas.

The easiest and quickest thing to do is to cut the Gordian knot of
the question with the sword of faith, or answer it with a belief in
a supernatural creation. The first article of the creed was given
to us in childhood as the foundation of all cosmic philosophy. It
is based on the Mosaic account of creation in the first chapter of
Genesis. As I have fully examined its scientific value in the second
chapter of my _History of Creation_, I may refer the reader thereto.
It is unquestionable that this myth still has a very great practical
influence; the great majority of the clergy cling to it because it is
found in the infallible "word of God." Most governments, which hold
blind faith to be an important element of education, include it in the
code for the elementary school. On the other hand, it is difficult
to find a man of science who will uphold it to-day. The gifted Louis
Agassiz made one of the most remarkable attempts to do this in
his _Essay on Classification_ (1858), a book that appeared almost
contemporaneously with Darwin's epoch-making _Origin of Species_, and
dealt with the general problems of biology from the directly opposite,
the mystic, point of view. According to Agassiz, each species of animal
or plant is an "incarnate thought of the Creator."

Differing from this Biblical fancy of the supernatural creation of
each species, two botanists, Wigand of Marburg and Reinke of Kiel,
have lately restricted the action of the celestial architect very
considerably; they have ascribed to him only the creation of the
primitive cells, which he is supposed to have endowed with the power
to develop into the higher organisms. Wigand assumed for the origin
of each species a special primitive cell and a long phylogenetic
development of this; Reinke prefers a stem, composed of a number of
species. These modern creative theories have no more scientific value
than that of Agassiz; they are equally based on pure superstition
(_cf._ chapters i.-iii.).

A different attitude from this irrational positive superstition is
the sceptical view of those scientists who regard the question of the
origin of life as insoluble or transcendental. Darwin and Virchow are
representatives of this agnostic position; they held that we know
nothing, and can know nothing, about the origin of the first organisms.
Darwin, for instance, explains in his chief work that he "has nothing
to do with the origin of the fundamental spiritual forces, or with
that of life itself." This is a complete abandonment of the task of
solving a scientific problem which must present as definite a subject
of inquiry to modern research as any other evolutionary problem. The
origin of life on our planet represents a fixed point in its history.
However, there is nothing to be said if a scientist chooses to make no
inquiry into it. A number of distinguished modern scientists maintain
this agnostic attitude; they are more or less convinced that the origin
of life is a natural process, but believe we have not as yet the means
to explain it.

Different, again, is a third attitude which regards the problem of
the origin of life as extremely difficult, yet capable of solution.
This is the position of Dubois-Reymond, for instance, who counts the
origin of life as the third great cosmic problem. Most of the modern
scientists who have worked on the problem are of this opinion, although
their views as to the way of solving it differ very much. We are
confronted, in the first place, with two essentially different views
which we may call the eternity-hypothesis and the theory of archigony
(or spontaneous generation). According to the first view, organic life
is eternal; according to the second, it began at a definite point of
time. The eternity-hypothesis has assumed two very different forms, one
of which has a dualistic and the other a monistic base. Helmholtz is a
representative of the former theory, and Preyer of the latter.

Hermann Eberhard Richter put forward, in 1865, the hypothesis that
infinite space is full throughout of the germs of living things,
just as it is of inorganic bodies; both of them are in a condition
of eternal development. When the ubiquitous germs reach a mature and
habitable cosmic body, which possesses heat and moisture in the proper
degrees for their development, they break into life, and may lead to
the formation of a whole world of living things. Richter conceives
these ubiquitous germs as living cells, and formulates the principle:
_Omne vivum ab æternitate e cellula_ (Every living thing is eternal and
from a cell). In much the same way the botanist Anton Kerner postulates
the eternity of organic life and its complete independence of the
inorganic world. But the difficulties encountered by this hypothesis,
in the indefinite form that Kerner gives it, are so great and so
obvious that his theory has won no recognition.

However, the "cosmozoic hypothesis" attained a great popularity when it
was afterwards taken up by two of the most distinguished physicists,
Hermann Helmholtz and Sir W. Thomson (Lord Kelvin). Helmholtz
formulated the alternative thus (in 1884): "Organic life either came
into existence at a certain period, or it is eternal." He declared for
the latter view, on the ground that we have not succeeded in producing
living organisms by artificial means. He supposes that the meteors
that roam about the universe might contain the germs of organisms,
and, under favorable conditions, these might reach the earth or other
planets and develop thereon. This cosmozoic hypothesis of Helmholtz
is untenable, because the physical features of space (the extreme
temperatures, the absolute dryness, the absence of atmosphere, etc.)
exclude the lasting existence of plasm on meteorites in the form of
organic germs with a capacity to live. The hypothesis is, moreover,
logically useless, since it does not solve, but postpones, the
question of the origin of organic life. If it is consistently worked
out, it leads to pure cosmological dualism.

Another and very different theory of the eternity of life has been
elaborated by Theodor Fechner (1873) and Wilhelm Preyer (1880). Both
these scientists extend the idea of life to the whole cosmos, and
reject the distinction that is usually drawn between the organic and
the inorganic. Fechner goes so far as to ascribe consciousness to the
whole universe and every single body in it, and regards individual
organisms merely as parts of one vast universal organism. His system
is, therefore, panpsychistic, and, at the same time, pantheistic, as he
somewhat mystically connects the idea of a conscious God with that of
a living universe. Preyer generally agrees with him in extending the
idea of life to the whole universe, and conceiving it as an organism.
He applies his theory in the symbolic sense which I alluded to on page
38, and described as impracticable. The fiery mass of the forming
earth is the gigantic organism, and Preyer gives the name of "life" to
its rotatory movement (or gravitational energy). As it cooled down,
the heavier metals (the dead inorganic masses) separated from it;
from the rest of it were formed first simple and afterwards complex
carbon-combinations, and finally albumin and plasm. This extension
of the word "organism" has very properly met with little approval in
biology. It only increases the confusion, and the difficulty of marking
off biological from abiological science, which is both practically
necessary and theoretically justified.

If, then, in our opinion, the eternity-hypotheses are of no more
value than the creation-hypotheses, we have left, for the purpose of
answering the great question of the origin of life, only the third
group of scientific theories which I have combined under the general
head or archigony. They start from the following points: 1. Organic
life is everywhere bound up with the plasm (or protoplasm), a chemical
substance of a viscous character, having albuminous matter and water as
its chief constituents. 2. The characteristic movements of this living
substance, to which we give the name of organic life, are physical and
chemical processes, that can only take place within certain limits of
temperature (between the freezing-point and boiling-point of water).
3. Beyond these limits organic life may in certain circumstances be
maintained for a time in a latent condition (apparent death, potential
life); but this latent condition is restricted to a certain (and
generally short) period. 4. As the earth, like all the other planets,
was for a long time in a state of incandescence, at a temperature
of several thousand degrees, living organisms (viscous albuminoids)
cannot possibly have existed on it, and so cannot be eternal. 5.
Fluid water, the first condition for the appearance of organic life,
cannot have formed on it until the crust at the surface had fallen
below boiling-point. 6. The chemical processes which first set in
at this stage of development must have been catalyses, which led to
the formation of albuminous combinations, and eventually of plasm.
7. The earliest organisms to be thus formed can only have been
plasmodomous monera, structureless organisms without organs; the
first forms in which the living matter individualized were probably
homogeneous globules of plasm, like certain of the actual chromacea
(_chroococcus_). 8. The first cells were developed secondarily from
these primitive monera, by separation of the central caryoplasm
(nucleus) and peripheral cytoplasm (cell-body).

The monistic hypothesis of abiogenesis, or autogony (=
self-development) in the strictly scientific sense of the word, was
first formulated by me in 1866 in the second book of the _General
Morphology_. The solid foundation for it was found in the monera I had
described, the very simple organisms without organs that had up to that
time been overlooked or thrust aside. It is of radical importance, in
giving a naturalistic solution of the problem of the origin of life, to
start from these structureless granules of living matter, and not--as
still generally happens--from the cell; these nucleated elementary
organisms could not be the earliest archigonous living things, but
must have been evolved secondarily from the unnucleated monera. Hence,
I made a very thorough study of these rudimentary organisms in my
_Monograph on the Monera_ (1870), and endeavored to formulate it more
clearly later on (in the first volume of the _Systematic Phylogeny_).
In regard to the chemical question of the first formation of plasm
and its inorganic preparation, Edward Pflüger conducted some valuable
investigations, and recognized that the radical of cyanogen was the
chief element of the living plasm. I may therefore distinguish two
different stages of the theory--my own older autogony-hypothesis and
the later cyanogen-hypothesis.

The theory of abiogenesis, or archigony, which I advanced in 1866, and
have developed in later writings, appeals directly to the biochemical
facts that modern vegetal physiology has firmly established. The
chief of these facts is that even the living green plant-cell has the
synthetic faculty of plasmodomism or carbon-assimilation; that is to
say, it is able to build up, by a chemical synthesis and reduction,
from simple inorganic compounds (water, carbonic acid, nitric acid,
and ammonia), the complex albuminous compounds which we call plasm
or protoplasm, and which we regard as the active living substance
and the true material basis of all vital function (_cf._ chapter
vi.). All botanists are now agreed that this most important process
of vegetal life, the fundamental process of all organic life and all
organization, is a purely chemical (or, in the wider sense, physical)
process, and that there is no question of a specific vital force or a
mystic constructor (like the famous "mechanical engineer of life"),
or any other transcendental agency, in connection with it. The tiny
chemical laboratory in which this remarkable organoplastic process
takes place under the influence of sunlight is, in the simplest
plants, the chromacea, either the whole homogeneous globule of plasm
(_chroococcus_) or its bluish-green surface-layer, which is active
as a chromatic principle (chromatophore). But in most plants these
reduction-laboratories are the chromatella or chromatophora, which
have been differentiated from the rest of the plasm of the cell, and
are colorless globular leucoplasts within its dark interior, or green
chromoplasts (or granules of chlorophyll) at its illumined surface.
My theory of archigony only assumes that this chemical process of
plasmodomism which we find repeated every second in every plant-cell
exposed to the sunlight, and which has become an "inherited habit" of
the green plant-cell, developed of itself at the beginning of organic
life; in other words, it is a catalytic process (or one analogous to
catalysis), the physical and chemical conditions of which were present
in the condition of organic nature at that time.

My hypothesis was very strongly confirmed twenty years ago by the
adhesion of the able botanist, Carl Nägeli. In his instructive work,
_A Mechanical-physiological Theory of Evolution_ (1884), he supported
all the principal ideas as to the natural origin of life which I
had advanced in 1866. He formulates the chief part of them in this
admirable principle:

 The origin of the organic from the inorganic is, in the first place,
 not a question of experience and experiment, but a fact deduced from
 the law of the constancy of matter and force. If all things in the
 material world are causally related, if all phenomena proceed on
 natural principles, organisms, which are formed of and decay into
 the same matter, must have been derived originally from inorganic
 compounds.

This excellent and clear declaration of a distinguished scientist and
profound thinker might be taken to heart by the "exact" scientists who
are always attacking the monistic theory of archigony as an unproved
hypothesis, or regard the whole problem as insoluble. Nägeli has,
moreover, proceeded to make a thorough study of the molecular processes
involved, and embodied the results in his idioplasm theory. He
believes that at the beginning of organization the definite autonomous
arrangement of the smallest homogeneous parts of the plasm was a
matter of the greatest importance. In his opinion these "micella" are
crystalline groups of molecules, arranged multifariously in strings and
parallel rows.

A similar and more elaborate attempt to give a physical explanation
of the processes of archigony and trace them to mechanical molecular
structures was made by Ludwig Zehnder in 1899 in his work on _The
Origin of Life_. He believes that the smallest and lowest life-unities
(the micellar strings of Nägeli and the biophora of Weismann,
corresponding to my plastidules) have a tubular shape, and so he calls
them "fistella." He supposes that these invisible molecular structures
are regularly arranged in millions in the plasma of the cell, and
differentiated in such a way that some will effect endosmosis, others
contraction, others the conduction of stimuli, and so on. As in
the similar work of Nägeli and others, the value of this molecular
hypothesis is that it stimulates us to attempt to conceive the mode of
the arrangement and movement of the molecules of plasm in the process
of archigony on physical principles.

A more interesting and notable attempt to penetrate into the mysterious
obscurity of the chemical processes in archigony was made in 1875
by the distinguished physiologist, Edward Pflüger, in his essay on
_Physiological Combustion in the Living Organism_. He starts from
the fact that the plasm (or protoplasm) is the material basis of all
vital phenomena, and that this living matter owes its properties to
the chemical properties of the albumin (whether we regard this as a
chemical unity, protein or protalbumin, or as a mixture of different
compounds). However, Pflüger sharply distinguishes between the living
albumin of the plasm out of which all organisms are built, and the dead
albumin, such as we find it, for instance, in the glairy albumin of the
hen's egg. Only the living albumin (plasm) decomposes of itself in a
slight degree, and to a greater extent under the influence of external
excitation; the dead albumin will remain intact for a long time under
favorable conditions. The cause of the extraordinary instability of the
living albumin is its intramolecular oxygen--that is to say, the oxygen
that is taken into the interior of the plasma-molecules in breathing,
and effects there a disassociation, surrounding the atoms and breaking
up the new-formed groups.

The real cause of this rapid decomposability of the plasm, and of the
accompanying formation of carbonic acid, is found in the cyanogen,
a remarkable body composed of an atom of carbon and an atom of
nitrogen, which, in conjunction with potassium, forms the well-known
and very virulent poison, cyanide of potassium. The non-nitrogenous
decomposition-products of the dead and the living albumin agree in the
main, but their nitrogenous products are totally different. Uric acid,
creotin, guanine, and the other decomposition products of plasm contain
the cyanogen-radical, and the most important of all, urea, can be
artificially produced from cyanic compounds, as Wöhler showed in 1828.
From this we may infer that the living albumin always contains the
cyanogen-radical, and that dead nutritive albumin does not. The belief
that it is cyanogen which gives its characteristic vital properties
to the plasm is supported by a number of analogies that we find to
exist between cyanide compounds, especially cyanic acid (C N O H.) and
the living albumin. Both bodies are fluid and transparent at a low
temperature, while they set at a higher; both of them break up in the
presence of water into carbonic acid and ammonia; both produce urea by
disassociation (by the intramolecular surrounding of the atoms, not by
direct oxydation). "The similarity of the two substances is so great,"
says Pflüger, "that I might describe cyanic acid as a semi-living
molecule." Both substances grow in the same way by concatenation of the
atoms, homogeneous groups of atoms joining together chainwise in large
masses.

There is an especial interest in connection with the theory of
archigony and its physical basis in the chemical fact that cyanogen and
its compounds--cyanide of potassium, cyanic acid, cyanide of hydrogen,
etc.--are only formed at incandescent heat; that is to say, when the
requisite inorganic nitrogenous compounds are put with glowing coals,
or the mixture is heated to incandescence. Other essential constituents
of albumin, such as carburetted hydrogen or alcohol-radical, can be
formed synthetically in heat. "Thus," says Pflüger, "nothing is clearer
than the possibility of the formation of cyanic compounds when the
earth was entirely or partially in a state of incandescence or great
heat. We see how extraordinarily all the facts of chemistry point to
fire as the force that has produced the constituents of albumin by
synthesis. Hence life was born from fire, and the chief conditions of
its appearance are associated with a time when the earth was a glowing
ball of fire. When we remember the incalculably long period in which
the surface of the earth was slowly cooling, we see that cyanogen, and
the compounds that contained cyanogen, and carburetted hydrogen, had
plenty of time and opportunity to follow out to any extent their great
tendency to the transposition and formation of polymeria (chains of
atoms), and, with the co-operation of oxygen and afterwards of water
and salts, to evolve into the self-decomposable albumin which is living
matter." In regard to the latter feature, it is well to emphasize the
fact that, as will be understood, there must have been a long series
of chemical intermediary stages between the incandescent formation of
cyanogen and the appearance of the aqueous living plasm.

Pflüger's cyanogen theory does not conflict with my monera theory, but
rather supplements it, by its careful and thoroughly scientific study
of a much earlier stage of primitive biogenesis--in a sense, the first
period of preparation for the formation of albumin. This must be well
borne in mind in view of the attacks which have lately been made on
it by Neumeister and other vitalists; it is supposed to be untenable,
because "there is an impassable gulf between cyanic compounds and
proteids." This criticism is answered by the living albumin itself,
which always contains in its nitrogenous decomposition products the
radical of cyanide or other substances (urea) that can be artificially
produced from cyanic compounds. Another objection is that "the cyanic
compounds which were formed in the heat must have very quickly perished
on the subsequent appearance of water." The objection has no weight,
since we can form no definite idea as to the special conditions of
chemical activity in those times. We can only say that the conditions
during this long period (embracing millions of years) were totally
different from those of chemical action at the surface of the earth
to-day. The real ground of the opposition of Neumeister and other
vitalists is their dualistic conception of nature, which will maintain
at all costs the deep gulf between the organic and inorganic worlds.

Max Verworn, in his _General Physiology_, has fully described and
criticised the various theories of the appearance of life on the earth.
He rightly attributes a great value to Pflüger's cyanogen theory,
because "it makes a strictly scientific study of the problem in close
relation to the facts of physiological chemistry, and goes thoroughly
into detail." He agrees with Pflüger when he expresses himself as
follows: "I would say, therefore, that the first albumin to be formed
was in point of fact living matter, endued with the property in all its
radicals of attracting especially homogeneous parts with great force
and preference, in order to build them chemically into the molecule,
and so grow indefinitely. On this view the living albumin need not
have a constant molecular weight, because it is a huge molecule in an
unceasing process of formation and decomposition, probably acting on
the ordinary chemical molecules as a sun does on a small meteor." This
theory, which I believe to be correct, is also maintained by many other
modern scientists who have made a particular study of the difficult
question of the nature and origin of the albuminoids.

Now that we have described the various modern theories of archigony
that are worth considering, and recognized with Nägeli that the
original development of the organic from the inorganic is a fact, we
may glance at the older theories which, under the name of "spontaneous
generation," afforded matter for a good deal of controversy. It is true
that they are now almost entirely abandoned, but the experiments in
connection with them excited a good deal of interest and led to many
misunderstandings.

The older hypotheses of "spontaneous generation" do not bear on our
problem of archigony (or the first development of living matter from
lifeless inorganic carbon compounds) but relate to the formation of
lower organisms out of the putrid and decomposing organic elements of
higher organisms. In order to distinguish these hypotheses from the
totally different theory of archigony, it is better to give them the
name of saprobiosis (an earlier name was necrobiosis), which means
the birth of living from dead (_nekron_) or putrid (_sapron_) organic
matter. Saprobiosis is preferable, because necrobiosis is better used
in a different sense, for the dead organic parts which gradually bring
about the death of the living body (see p. 106). It was believed in
ancient times that lower organisms could arise from the dead remains of
higher organisms, such as fleas from manure, lice from morbid pustules
in the skin, moths from old furs, and mussels from slime in the water.
As these stories were supported by the authority of Aristotle, and
on that account believed by St. Augustine and other fathers, and
reconciled with the faith, they were held until the beginning of the
eighteenth century. Even in the year 1713 the botanist Heucherus stated
that the green duck-weed (_lemna_) is only condensed grease from the
surface of foul standing water, and that water-cress was formed from it
in fresh running water.

The first scientific refutation of these old stories was made by the
Italian physician, Francisco Redi, in 1674, on the basis of very
careful experiment: he was persecuted for "unbelief" on that account.
He showed that all these animals arose from eggs that had been
deposited by female animals in dung, skin, fur, slime, etc. But at that
time the proof could not be extended to the tape-worms, maw-worms,
and other intestinal animals (_entozoa_), which live inside other
animals (in the bowels, blood, brain, or liver). It was still believed
that these arise from diseased parts of the host-animals in which
they live, until about the middle of the nineteenth century. It was
not until 1840-1860 that it was shown by the experiments of Siebold,
Leuckart, Van Beneden, Virchow, and other famous biologists, that all
these intestinal animals have come from without into the animals they
live in, and propagate there by eggs. Of late years the proof has been
applied all round.

On the other hand, the hypothesis of saprobiosis retained its position
until quite recently for one section of the smallest and lowest
organisms, the microscopic forms of life, invisible to the naked eye,
which were formerly called infusoria, and which we now call by the
wider name of protists or unicellulars. When Leeuwenhoek discovered the
infusoria in 1675 with the newly invented microscope, and showed that
they arise in great quantities in infusions of hay, moss, flesh, and
other putrid organic substances, it was generally believed that they
were spontaneously generated there. The Abbé Spallanzani showed in 1687
that no infusoria appear in these infusions if they are well boiled and
the vessel is carefully closed; the boiling kills the germs in them,
and the exclusion of air prevents the entrance of fresh germs. In spite
of this, many microscopists still believed that certain infusoria,
particularly the very small and simple bacteria, could be born directly
from putrid or diseased tissues of organisms, or from decomposing
organic fluids; the opinion was maintained by Pouchet at Paris in 1858,
and afterwards by Charlton Bastian. The controversy about the subject
moved the Paris Academy in 1858 to offer a prize for "careful research
that would throw new light on the question of spontaneous generation."
It fell to the famous Louis Pasteur, who proved, by a series of
ingenious experiments, that there are everywhere in the atmosphere
numbers of germs of microbes or microscopic organisms floating among
the dust particles, and that these grow and reproduce when they reach
water. Not only infusoria, but also small highly organized plants and
animals--such as lichens, mosses, rotifers, and tardigrades--can live
for months in a desiccated condition, be carried in all directions
by the wind, and reawaken into life when they reach water. On the
other hand, Pasteur showed convincingly that organisms never appear
in infusions of organic substances when they are sufficiently boiled
and the atmosphere that reaches them has been chemically purified. He
summed up the results of his rigorous experiments, which were confirmed
by Robert Koch and other bacteriologists, and gave rise to the modern
precautions as to disinfection, in the maxim: "Spontaneous or equivocal
generation is a myth."

The famous experiments of Pasteur and his successors had destroyed the
myth of saprobiosis, but not the theory of archigony. These entirely
different hypotheses are still very frequently confused, because the
old title of "spontaneous generation" is used for both. We still read
sometimes that the "unscientific" belief in abiogenesis has been
definitely refuted by these experiments, and that the question of
the origin of life has thus become an insoluble enigma. There is an
astonishing superficiality and lack of discernment in such remarks;
they would hardly be possible in any other branch of science. But in
biology--many of its distinguished representatives continue to say--we
have only to observe and correctly describe facts; the formation
of clear ideas and the indulgence in reflection on the facts are
unnecessary and dangerous, and, therefore, to be avoided! It is due
to this pitiable condition of biological methods of research that
our hypothesis of archigony is still attacked, or else ignored. Why?
Because the false hypothesis of saprobiosis, which has absolutely
nothing in common with it but the name "spontaneous generation," has
been refuted by the experiments of Pasteur and his colleagues![9]
These experiments prove nothing whatever beyond the fact that new
organisms are not formed in certain infusions of organic matter--under
definite, artificial conditions. They do not even touch the important
and pressing question, which alone interests us: "How did the earliest
organic inhabitants of our earth, the primitive organisms, arise from
inorganic compounds?"

The great popularity of the famous experiments of Pasteur on
spontaneous generation, and the unfortunate confusion of ideas which
was caused by the false interpretation of his results, make it
necessary for me to say a word on the general value of scientific
experiments in many questions. Since Bacon introduced experiment into
science three hundred years ago, and gave it a logical basis, both
our speculative knowledge of nature and the practical application
of our knowledge made remarkable progress. New methods of research
made it possible for modern workers to penetrate far more deeply into
the nature of phenomena than the older thinkers had done, who had no
knowledge of experiment. Especially in the nineteenth century the
development of the experimental method, or the putting of a question to
nature, led to enormous advances in the various sciences.

In the subject we are considering the question to be put to nature
is: "Under what conditions and in what manner is living matter (or
plasm) formed from lifeless inorganic compounds?" We may confidently
assume that in the period when archigony took place--the time when
organic life first appeared on the cooled surface of the earth, at
the beginning of the Laurentian Age--the conditions of existence were
totally different from what they are now; but we are very far from
having a clear idea of what they were, or from being able to reproduce
them artificially. We are just as far from having a thorough chemical
acquaintance with the albuminous compounds to which plasm belongs.
We can only assume that the plasma-molecule is extremely large, and
made up of more than a thousand atoms, and that the arrangement and
connection of the atoms in the molecule are very complicated and
unstable. But of the real features of this intricate structure we
have as yet no conception. As long as we are ignorant of this complex
molecular structure of albumin, it is useless to attempt to produce
it artificially. Yet in this position of the matter we would seek
to produce that great wonder of life, the plasm, artificially, and
when the experiment miscarries (as we should expect) we cry out:
"Spontaneous generation is impossible."

When we carefully consider the intelligent experiments that have been
made in regard to archigony in the light of these facts, it is clear
that their negative result does not in the slightest degree affect our
question. The much-admired experiments of Pasteur and his colleagues
prove merely that in certain artificial conditions infusoria are not
formed in decomposing organic compounds (or the dead tissues of highly
organized histona); they cannot possibly prove that saprobioses of this
kind do not take place under other conditions. They tell us nothing
whatever about the possibility or reality of archigony; in the form
in which I put the scientific hypothesis in 1866 it is completely
untouched by all these experiments. It remains intact as the first
attempt to give a provisional reply--if only in the form of a temporary
hypothesis--on the basis of modern science to one of the chief
questions of natural philosophy.

In my _General Morphology_ (1866), and afterwards in my _Biological
Studies on the Monera and other Protists_, and the first volume of
my _Systematic Phylogeny_ (1894), I attempted to sketch in detail
the stages of the process to which I give the name of archigony. I
distinguished two principal stages--_autogony_ (the formation of the
first living matter from inorganic nitrogenous carbon-compounds) and
_plasmogony_ (the formation of the first individualized plasm; the
earliest organic individuals in the form of monera). In more recent
efforts I have made use of the important results reached by Nägeli
(1884) in his investigations of the same subject. In regard to some
important points relating to the chemico-physical part of the question,
Nägeli has, in his _Mechanico-physiological Theory of Evolution_
(chapter ii.), gone more into the details of the process of archigony.
To the earliest living things, which were formed by "unicellular
organization" of the plasm out of simple inorganic compounds, he
gives the name of _probia_ or _probionta_, and thinks that these had
an even simpler structure than my monera. This view seems to rest on
a misunderstanding. Nägeli does not strictly follow my definition,
"organisms without organs" (that is to say, structureless living
particles of plasm without morphological differentiation), but he has
in mind the individual rhizopod-like organisms which I had at first
described as monera--_protamœba_, _protogenes_, _protomyxa_, etc. In
my present view the chromacea, or plasmodomous phytomonera, are much
more important than these plasmophagous zoomonera. It is curious that
Nägeli does not make thorough use of their primitive organization for
the establishment of his theory, although he has had the great merit of
describing these most primitive of all living organisms as unicellular
algæ (1842). As a matter of fact, the simplest chromacea (chroococcus
and related forms) approach so closely to his hypothetical probia
or probionta that the only things we can regard as the rudiments of
organization in the chroococcacea are the secretion of a protective
membrane about the homogeneous plasma-globule and the separation of
the blueish-green cortical zone from the colorless central granule.
The more important of the further conclusions of Nägeli are those
which relate to the mode of the primitive abiogenesis and the frequent
repetition of this physical process.

Recently Max Kassowitz, in the second volume of his _General Biology_
(1899), has gone fully into the various stages of the process of
archigony, as a sequel to his metabolic theory of the building up and
decay of plasm, from the point of view of physiological chemistry. He
says very truly that the development of living from lifeless matter
must not be conceived as a sudden leap; the very complicated chemical
unities which now form the basis of life have been slowly and gradually
evolved during an incalculably long period by the way of substitution
for simpler compounds. We may join these views--which generally accord
with my earlier deductions--with Pflüger's cyanogen theory, and so draw
up the following theses:

1. A preliminary stage to archigony is the formation of certain
nitrogenous carbon-compounds which may be classed in the cyanic
group (cyanic acid, etc.). 2. When the crust of the earth stiffened,
water was formed in the fluid condition; under its influence, and in
consequence of the great changes in the carbonic-acid laden atmosphere,
a series of complicated nitrogenous carbon-compounds were formed from
these simple cyanic compounds, and these first produced albumin (or
protein). 3. The molecules of albumin arranged themselves in a certain
way, according to their unstable chemical attractions, in larger groups
of molecules (pleona or micella). 4. The albumin-micella combined to
form larger aggregations, and produced homogeneous plasma-granules
(plassonella). 5. As they grew the plassonella divided, and
formed larger plasma-granules of a homogeneous character: monera
(= probionta). 6. In consequence of surface-strain or of chemical
differentiation, there took place a separation of the firmer cortical
layer (membrane) from the softer marrow layer (central granule), as in
many of the chromacea. 7. Afterwards the simplest (nucleated) cells
were formed from these unnucleated cytodes, the hereditary mass of the
plasm gathering within the monera and condensing into a firm nucleus.

It is an interesting, but at present unanswered, question whether the
process of archigony only occurred once in the course of time or was
frequently repeated. Reasons can be given for both views. Pflüger
says: "In the plant the living albumin only continues to do what it
has done ever since its origin--constantly to regenerate itself or to
grow; hence I believe that all the albumin in the world comes from that
source. On that account I doubt if spontaneous generation takes place
in our time. Moreover, comparative biology directly shows that all life
has come from one single root." However, this view does not exclude the
possibility of the chemical process of spontaneous plasmodomism having
been frequently repeated--under like conditions--in the same form in
primordial times.

On the other side, Nägeli especially has pointed out that there is
no reason to prevent us from thinking that archigony was repeated
several times, even down to our own day. Whenever the physical
conditions for the chemical process of plasmodomism were given, it
might be repeated anywhere at any time. As to locality, the sea-shore
probably affords the most favorable conditions; as, for instance, on
the surface of fine moist sand the molecular forces of matter in all
its conditions--gaseous, fluid, viscous, and solid--find the best
conditions for acting on each other. It is a fact that to-day all the
various evolutionary forms of living matter--from the simplest moneron
(chroococcus) to the plain nucleated cell, from this to the highly
organized cell of the radiolaria and infusoria, from the simple ovum to
the most elaborate tissue-structure in the higher plants and animals,
from the amphioxus to man--come in an order of succession. There are
only two ways of explaining this fact: either the simplest living
organisms, the chromacea and bacteria, the palmella and amœbæ, have
remained unchanged or made very little advance in organization since
the beginning of life--more than a hundred million years; or else
the phylogenetic process of their transformation has been frequently
repeated in the course of this period, and is being repeated to-day.
Even if the latter were the case, we should hardly be in a position to
learn it by direct observation.

Assuming that the simplest organisms are still formed by abiogenesis,
the direct observation of the process would probably be impossible,
or at least extremely difficult, for the following reasons: 1. The
earliest and simplest organisms are most probably globular particles
of plasm, without any visible structure, like the simplest living
chromacea (_chroococcus_). 2. These plasmodomous monera cannot be
distinguished from the chromoplasts (chlorophyll-granules), which live
inside plant-cells, and may continue after the death of the cells
to multiply independently by cleavage. 3. We must admit with Nägeli
that the original size of these probionta (in spite of the relatively
colossal size of their molecules) is very small--much too small to
come within the range of the best microscope. 4. In the same way the
primitive metabolism and the slow, simple growth of these monera would
not come within direct observation. 5. As a matter of fact, we do often
find in stagnant water, and in the sea, tiny granules which consist, or
seem to consist, of plasm. We usually regard them as detached portions
of dead animals or plants; little isolated chlorophyll-granules that
may be found everywhere are looked upon as rejected products of vegetal
cells. But who could refute the assumption that they are really
plassonella or young monera, which grow slowly and unite with similar
particles to form larger plasmic bodies?

It is often objected to our naturalistic and monistic conception of
archigony that we have not yet succeeded in forming albuminous bodies,
and especially plasm, in our chemical laboratories by artificial
synthesis; from this the perverse dualistic conclusion is drawn that
it is only supernatural vital forces that can do this. It is forgotten
that we do not yet know the complicated structure of albuminous
bodies, and that we do not yet know what really happens inside the
green chlorophyll-granules which in every plant-cell convert the
radiant energy of sunlight into the virtual energy of the new-formed
plasm. How can we be expected to reproduce synthetically, with the
imperfect and crude methods of present chemistry, an elaborate chemical
process the nature of which is not analytically known to us? However,
the worthlessness of this sceptical objection is obvious: we can
never claim that a natural process is supernatural because we cannot
artificially reproduce it.




XVI

THE EVOLUTION OF LIFE

 Inorganic and organic evolution--Biogenesis and
 cosmogenesis--Mechanical evolution--Mechanics of phylogenesis--Theory
 of selection--Theory of idioplasm--Phyletic vital force--Theory of
 germ-plasm--Progressive heredity--Comparative morphology--Germ-plasm
 and hereditary matter--Theory of mutation--Zoological and botanical
 transformism--Neo-Lamarckism and Neo-Darwinism--Mechanics of
 ontogenesis--Biogenetic law--Tectogenetic ontogeny--Experimental
 evolution--Monism and biogeny.


I fully explained in my _General Morphology_ (1866) the profound
importance of the science of evolution in relation to our monistic
philosophy. A popular synopsis of this is given in my _History of
Creation_, and is briefly repeated in the thirteenth chapter of the
_Riddle_. I must refer the reader to these works, especially the
latter, and confine myself here to a consideration of some of the
principal general questions of evolution in the light of modern
science. The first thing to do is to compare the conflicting views on
the nature and significance of biogenesis which still face each other
at the beginning of the twentieth century.

The essential unity of inorganic and organic nature, which I endeavored
to establish in the second book of the _General Morphology_, and the
significance of which I explained in the fourteenth chapter of the
_Riddle_, is found through the whole course of its development, in
the causes of phenomena and their laws. Hence, in dealing with the
evolution of organisms, we reject vitalism and dualism, and maintain
our conviction that it can always be traced to physical forces (and
especially chemical energy). As we regard plasm as the basis of it
(chapter vi.), we may say that organic evolution depends on the
mechanics and chemistry of the plasm. We postulate no supernatural
vital force for the explanation of physiological functions, and we are
just as far from admitting it as regulator or agency of the biogenetic
process.

If we understand by biogeny the sum total of the organic evolutionary
processes on our planet, by geogeny the processes at work in the
formation of the earth itself, and by cosmogony those that produced the
whole world, biogeny is clearly only a small part of geogeny, and this
in turn only a small section of the vast science of cosmogony. This
important relation is evident enough, yet often overlooked; it holds
both of time and space. Even if we suppose that the biogenetic process
occupied more than a hundred million years, this period is probably
much shorter than that which our planet has needed for its development
as a cosmic body--from the first detachment of the nebular ring from
the shrinking body of the sun to its condensation into a rotating
sphere of gas, and from this to the formation of the incandescent
globe, the stiffening of the crust at its surface, and finally the
downpour of fluid water. It was not until this last stage that carbon
could begin its organogenetic activity and proceed to the formation of
plasm. But even this long geogenetic process is, as regards space and
time, only a very small part of the illimitable history of the world.
If we further assume that organic life develops on other cosmic bodies
(_Riddle_, chapter xx.) in the same way as on our earth under like
conditions, the whole sum of all these biogenetic processes is only a
small part of the all-embracing cosmogenetic process. The vitalistic
belief that its mechanical course was interrupted from time to time
by the supernatural creation of organisms is opposed to pure reason,
the unity of nature, and the law of substance. We must, therefore, hold
fast above all to the conviction that all biogenetic processes are
just as reducible to the mechanics of substance as all other natural
phenomena.

The mechanical and natural character of the development of inorganic
nature, the earth and the whole material world, was established
mathematically at the end of the eighteenth century by the great
atheist Laplace in his _Mécanique Céleste_ (1799). The similar
cosmogony which Kant had expounded in 1755 in his _General Natural
History and Theory of the Heavens_ only obtained recognition at a
later date (_Riddle_, chapter xiii.). But the possibility of giving
a mechanical explanation of organic nature was not seen until Darwin
provided a solid foundation for the theory of descent by his theory of
selection in 1859. I made the first comprehensive attempt to do this in
1866 in my _General Morphology_, the aim of which is expressed in the
title: "General outlines of the science of organic forms, mechanically
grounded on Darwin's improvement of the theory of descent." Especially
in the second volume of the work, the "General Evolution of Organisms,"
I endeavored to show that both sections of the science, ontogeny (or
embryology) and phylogeny, can be reduced to physiological activities
of the plasm, and so explained mechanically, in the wider meaning of
the word.

When I stated the nature and the aim of phylogeny in 1866, most
biologists regarded my attempt as unjustifiable, as they did Darwinism
itself, of which it was a natural consequence. Even the famous Émil
Dubois-Reymond, to whom as a physiologist it should have been welcome,
described it as "a poor romance"; he compared my first attempts
to construct the genealogical tree of the organic classes, on the
evidence of paleontology, comparative anatomy, and ontogeny, to the
hypothetical labors of philologists to draw up the genealogical tree
of the legendary Homeric heroes. As a matter of fact, I had myself
described my imperfect effort as merely a provisional sketch, as a
temporary hypothesis that would open the way for later and better
research. A single glance at the immense literature of phylogeny
to-day shows how much has been done since in this province, and how
far we have advanced in the establishment of the features of evolution
by means of the united labors of numbers of able paleontologists,
anatomists, and embryologists. Ten years ago I attempted, in the three
volumes of my _Systematic Phylogeny_, to give a comprehensive statement
of the results attained. My chief aim was, on the one hand, to
construct a natural system of organisms on the basis of their ancestral
history, and on the other hand to prove the mechanical character of
the phylogenetic process. All the activities of organisms which are at
work in the transformation of species and the production of new ones
in the struggle for existence may be reduced to their physiological
functions--to growth, nutrition, adaptation, and heredity; and these
again to the mechanics and chemistry of the plasm. The struggle for
life is itself a mechanical process, in which natural selection uses
the disproportion between the excess of germs and the restricted
means of existence, in conjunction with the variability of species,
in order to produce new purposive structures mechanically and without
any preconceived design. This teleological mechanicism has no need of
a mysterious design or finality; it takes its place in the general
order of mechanical causality which controls all the processes in the
universe. Natural finality is only a special instance of mechanical
causality. The one is subordinate to the other, not opposed to it, as
Kant would have it.

The effort that the great Lamarck made in 1809, in his _Philosophie
Zoologique_, to establish transformism deserves high appreciation from
monists, because it was the first attempt to give a natural explanation
of the origin of the countless species of organic forms which inhabit
our planet. Up to that time it had been the fashion to attribute their
origin to a miraculous intervention of the Creator. This metaphysical
creationism had now to face physical evolutionism. Lamarck explained
the gradual formation of organic species by the interaction of
two physiological functions--adaptation and heredity. Adaptation
consists in the improvement of organs by use, and degeneration by
disuse; heredity acts by transmitting the features thus acquired to
posterity. New species arise by physiological transformation from
older species. The fact that this great thought was overlooked for
half a century does not detract from its profound significance. But it
only obtained general recognition when Darwin had supplemented it and
filled up its causal gaps by the theory of selection in 1859. Apart
from this specifically Darwinian feature (whether it be true or not),
the fundamental idea of transformism is now generally received; it
is admitted to-day even by metaphysicians who maintained a spirited
opposition to it thirty years ago. The fact of the progressive
modification of species is only intelligible on Lamarck's theory
that the actual species are the transformed descendants of older
species. In spite of all the learning and zeal with which the theory
has been attacked, it has proved irrefutable; nor can any one suggest
a better theory to replace it. This may be said particularly of its
chief consequence--the descent of man from a series of other mammals
(proximately from the apes).

The high value of Darwin's theory of selection for the monistic biology
is now acknowledged by all competent and impartial authorities
on the science. In the course of the forty-four years since it
found its way into every branch of biology, it has been employed
in more than a hundred large works and several thousand essays in
explaining biological phenomena. This alone is enough to show its
profound importance. Hence it is mere ignorance of the subject and
its literature to say, as has been done several times of late, that
Darwinism is in decay, or even "dead and buried." However, absurd
writings of this kind (such as Dennert's _At the Death-bed of
Darwinism_) have a certain practical influence, because they fall
in with the prevailing superstition in theology and metaphysics.
Unfortunately, they also seem to obtain notice from the circumstance
that a few botanists persistently attack the Darwinian theory. One of
the most conspicuous of these is Hans Driesch, who affirms that all
Darwinists (and therefore the great majority of modern biologists) have
softening of the brain, and that Darwinism is (like Hegel's philosophy)
the delusion of a generation. The arrogance of this conceited writer is
about equal to the obscurity of his biological opinions, the confusion
of which is covered by a series of most extravagant metaphysical
speculations. All these attacks have lately been met very ably by
Plate in his work, _On the Significance of the Darwinian Principle
of Selection and the Problem of the Foundation of Species_ (second
edition, 1903). The most thorough of recent defences of Darwinism
is that made by August Weismann in his _Lectures on the Theory of
Descent_ (1902) and other works. But the distinguished zoologist
goes too far when he seeks to prove the omnipotence of selection and
wishes to ground it on an untenable molecular hypothesis--the theory
of germ-plasm, which we will consider presently. Apart from these or
other exaggerations, we may say with Weismann that Lamarck's theory of
descent received a sound causal basis by Darwin's theory of selection.
Its real foundations are these three phenomena: heredity, adaptation,
and the struggle for existence. All three are, as I have often said,
of a purely mechanical and not a teleological nature. Heredity is
closely bound up with the physiological function of reproduction, and
adaptation with nutrition; the struggle for life follows logically and
mathematically from the disproportion between the number of potential
individuals (germs) and of actual individuals that grow to maturity and
propagate the species.

When I had, in my _General Morphology_, endeavored to gain acceptance
for Darwin's theory of selection, and had presented evolution as a
comprehensive theory from the point of view of the monistic philosophy,
a number of works, sometimes of value, appeared, which made special
studies of the various parts of the immense province. Eighteen years
afterwards a greater work was published, which started from the same
monistic principles, but reached the same conclusion by a different
way. In 1884 Carl Nägeli, one of our ablest and most philosophic
botanists, issued his _Mechanical-physiological Theory of Evolution_.
This interesting book consists of various parts. It is especially
notable that evolution is presented in it as the one possible
and natural theory of the origin of species; even morphology and
classification are treated explicitly as "phylogenetic sciences." The
chapter on archigony--a dark and dangerous problem that is generally
avoided by scientists!--is one of the best that has been written on the
subject. On the other hand, Nägeli rejects Darwin's theory of selection
altogether, and would explain the origin of species by an inner
"definitely directed variation," independently of the conditions of
existence in the outer world. As Weismann has properly observed, this
internal principle of evolution, which dispenses with adaptation in
the true sense of the word, is at the bottom merely a "phyletic vital
force." It is not made more acceptable by Nägeli when he builds up a
subtle metaphysical system on it and postulates a special "principle
of isagitation." But the idioplasm theory he connects with it is of
some value, since it goes more fully into the differentiation of the
cell-plasm into two physiologically different parts--the idioplasm of
the hereditary matter and the trophoplasm as nutritive matter of the
cell.

The vitalist and teleological idea of an internal principle of
evolution, that determines the origin of animal and plant species
independently of the environment and its conditions, is not only
found in the "mechanical-physiological" theory of Nägeli, but also in
several other attempts to explain the agencies of the transformation of
species. All these efforts are welcomed by the academic philosophers
with their Kantist dualism (mechanicism on the right, teleology on
the left), and who are particularly anxious to save the supernatural
element, Reinke's "cosmic intelligence," or the wisdom of the Creator,
or the divine creative thought. All these dualistic and teleological
efforts have the same fault: they overlook, or fail to appreciate
properly, the immense influence of the environment on the shaping
and modification of organisms. When, moreover, they deny progressive
heredity and its connection with functional adaptation, they lose the
chief factor in transformation. This applies also to the theory of
germ-plasm.

The desire to penetrate deeper into the mysterious processes that
take place in the plasm in the physiological activities of heredity
and adaptation has led to the formulation of a number of molecular
theories. The chief of these are the pangenesis theory of Darwin
(1878), my own perigenesis theory (1876), the idioplasm theory of
Nägeli (1884), the germ-plasm theory of Weismann (1885), the mutation
theory of De Bries, etc. As I have already dealt with these in the
sixth chapter (as well as in the ninth chapter of the _History of
Creation_), I may refer the reader thereto. None of these or similar
attempts has completely solved the very difficult problems in question,
and none of them has been generally received. There is, however, one
of them that we must consider more closely, because it is not only
regarded by many biologists as the greatest advance of the theory of
selection since Darwin, but it also touches the roots of several of
the chief problems of biogeny. I mean the much-discussed germ-plasm
theory of August Weismann (of Freiburg), one of our most distinguished
zoologists. He has not only promoted the theory of descent by his
many writings during the last thirty years, but has also put in its
proper light the great importance and entire accuracy of the theory of
selection. But, in his efforts to provide a molecular-physiological
basis for it, he has proceeded by way of metaphysical speculation to
frame a quite untenable theory of the plasm. While fully recognizing
the ability and consistency and the able treatment which Weismann
has shown, I am compelled once more to dissent from him. His ideas
have recently been completely refuted by Max Kassowitz (1902) in his
_General Biology_, and Ludwig Plate in the work I mentioned on the
Darwinian principle of selection. We need not go into the details of
the complicated hypothesis as to the molecular structure of the plasm
which Weismann has framed in support of his theory of heredity--his
theory of biophora, determinants, ideas, etc.--because they have no
theoretical basis and are of no practical use. But we must pass some
criticism on one of their chief consequences. In the interest of his
complicated hypotheses, Weismann denies one of Lamarck's most important
principles of transmutation--namely, the inheritance of acquired
characters.

When I made the first attempt in 1866 to formulate the phenomena of
heredity and adaptation in definite laws and arrange these in series,
I drew a distinction between conservative and progressive heredity
(chapter ix., _History of Creation_). Conservative heredity, or the
inheritance of inherited characters, transmits to posterity the
morphological and physiological features which each individual has
received from his parents. Progressive heredity, or the inheritance of
acquired characters, transmits to offspring a part of those features
which were acquired by the parents in the course of their individual
lives. The chief of these are the characters that are caused by the
activity of the organs themselves. Increase in the use of the organs
causes a greater access of nourishment and promotes their growth;
decrease in the exercise of organs has the contrary effect. We have
examples at hand in the modification of the muscles or the eyes, the
action of the hand or throat in painting or singing, and so on. In
these and all the arts the rule is: Practice makes perfect. But this
applies almost universally to the physiological activity of the plasm,
even its highest and most astounding function--thought; the memory and
reasoning capacity of the phronema are improved by constant exercise of
the cells which compose this organ, just as we find in the case of the
hands and the senses.

Lamarck recognized the great morphological significance of this
physiological use of the organs, and did not doubt that the
modification caused was transmitted to offspring to a certain extent.
When I dealt with this correlation of direct adaptation and progressive
heredity in 1866, I laid special stress on the "law of cumulative
adaptation" (_General Morphology_, ii., p. 208). "All organisms undergo
important and permanent (chemical, morphological, and physiological)
changes when acted on by a change in its life-conditions, slight in
itself, but continuing for a long time or being frequently repeated."
At the same time I pointed out that in this case two groups of
phenomena are closely connected which are often separated--namely,
cumulative heredity: firstly _external_, by the action of the external
conditions (food, climate, environment, etc.), and secondly _internal_,
by the reaction of the organism, the influence of internal conditions
(habit, use and disuse of organs, etc.). The action of outer influences
(light, heat, electricity, pressure, etc.) not only causes a reaction
of the organism affected (energy of movement, sensation, chemosis,
etc.), but it has an especial effect as a trophic stimulus on its
nutrition and growth. The latter element has been particularly studied
by Wilhelm Roux; his functional adaptation (1881) coincides with my
cumulative adaptation, the close relation of which to correlative
adaptation I had pointed out in 1866. Plate has recently given this
"definitely directed variation" the name of ectogenetic orthogenesis,
or, briefly, ectogenesis.

The controversy about progressive heredity still continues here and
there. Weismann completely denies it, because he cannot bring it into
harmony with his germ-plasm theory, and because he thinks there are
no experimental proofs in support of it. A number of able biologists
agree with him, led away by his brilliant argumentation. However,
many of them foolishly lay great stress on experiments in heredity
which prove nothing; for instance, the fact that the offspring of a
mammal that has had its tail cut off do not inherit the feature. A
number of recent observations seem to prove that in a few cases even
defects of this sort (when they have caused profound and lasting
disease of the part affected) may be transmitted to offspring.
However, as far as the formation of new species is concerned, the
fact is of no consequence; in this it is a question of cumulative or
functional adaptation. Experimental proofs of this are difficult to
find, if one wants a strict demonstration of the type of physical
experiments; the biological conditions are generally too complicated
and offer too many weak points to rigorous criticism. The beautiful
experiments of Standfuss and C. Fisher (Zurich) have shown that changes
in the environment (such as temperature or food) can cause striking
modifications that are transmitted to offspring. In any case, there are
plenty of luminous proofs of progressive heredity in the vast arsenal
of morphology, comparative anatomy, and ontogeny.

Comparative anatomy affords a number of most valuable arguments for
other phylogenetic questions as well as progressive heredity; and the
same may be said of comparative anatomy and comparative ontogeny. I
have collected and illustrated a good many of these proofs in the new
edition of my _Anthropogeny_. However, in order to understand and
appreciate them aright, the reader must have some acquaintance with
the methods of critical comparison. This means not only an extensive
knowledge of anatomy, ontogeny, and classification, but also practice
in morphological thinking and reasoning. Many of our modern biologists
lack these qualifications, especially those "exact" observers who
erroneously imagine they can understand vast groups of phenomena by
accurate description of detailed microscopic structures, etc. Many
distinguished cytologists, histologists, and embryologists have
completely lost the larger view of their work by absorption in these
details. They even reject some of the fundamental ideas of comparative
anatomy, such as the distinction between homology and analogy;
Wilhelm His, for instance, declared that these "academic ideas" are
"unreliable tools." On the other hand, physiological experiments ought
to contribute to the solution of morphological problems, and of these
they can say nothing. To show the incalculable value of comparative
anatomy for phylogeny, I need only point to one of its most successful
departments, the skeleton of the vertebrates, the comparison of the
various forms of the skull, the vertebral column, the limbs, etc. It
is not in vain that for more than a hundred years gifted scientists,
from Goethe and Cuvier to Huxley and Gegenbaur, have devoted years
of laborious research to the methodical comparison of these similar
yet dissimilar forms. They have been rewarded by the discovery of the
common laws of structure, which can only be explained in the sense of
modern evolution by descent from common ancestors.

We have a striking example of this in the limbs of mammals, which, with
the same internal skeletal structure, show a very great variety in
outer form--the slender bones of the running carnivora and ungulates,
the oar-bones of the whale and seal, the shovel-bones of the mole and
hypudæus, the wings of the bat, the climbing bones of the ape, and the
differentiated limbs of the human body. All these different skeletal
forms have descended from the same common stem-form of the oldest
Triassic mammals; their various forms and structures are adapted in
scores of ways to different functions; but they rise _through_ these
functions, and all these functional adaptations can only be understood
by progressive heredity. The theory of germ-plasm gives no causal
explanation whatever of them.

The majority of recent biologists are of opinion that of the two chief
constituents of the nucleated cell the cytoplasm of the cell-body
discharges the function of nutrition and adaptation, while the
caryoplasm of the nucleus accomplishes reproduction and heredity.
I first advanced this view in the ninth chapter of the _General
Morphology_ (in 1866); and it was afterwards solidly and empirically
established by the excellent investigations of Eduard Strasburger, the
brothers Oscar and Richard Hertwig, and others. The elaborate finer
structures which these observers discovered in cell-division led to
the theory that the colorable part of the nucleus, chromatin, is the
real hereditary matter, or the material substratum of the energy of
heredity. Weismann added the theory that this germ-plasm lives quite
separately from the other substances in the cell, and that the latter
(the soma-plasm) cannot transmit to the germ-plasm the characters it
has acquired by adaptation. It is on the strength of this theory that
he opposes progressive heredity. The representatives of the latter
(including myself) do not accept this absolute separation of germ-plasm
from body-plasm; we believe that even in the process of cell-division
in the unicellular organism there is partial blending of the two kinds
of plasm (caryolysis), and that in the multicellular organism of the
histona also the harmonious connection of all the cells by their
plasma-fibres makes it possible enough for all the cells in the body to
act on the germ-plasm of the germ-cells. Max Kassowitz has shown how we
can explain this influence by the molecular structure of the plasm.

At the beginning of the twentieth century a new biological theory
aroused a good deal of interest, and was welcomed by some as an
experimental refutation of Darwin's theory of selection and by others
as a valuable supplement to it. The distinguished botanist Hugo de
Bries (of Amsterdam) gave an interesting lecture at the scientific
congress at Hamburg in 1901 on "The Mutations and Mutation-periods
in the Origin of Species." Supported by many years of experiments in
selection and some ingenious speculations, he thinks he has discovered
a new method of the transformation of species, an abrupt modification
of the specific form at a bound, and so discredited Darwin's theory of
their gradual change through long periods of time. In a large work on
_Experiments and Observations on the Origin of Species in the Plant
Kingdom_ (1903), De Bries has endeavored to demonstrate the truth of
his theory of mutation. The warm approval which it won from a number
of eminent botanists, and especially vegetal physiologists, was not
shared by zoologists. Of these Weismann, in his _Lectures on the
Theory of Descent_ (1902, ii. p. 358), and Plate in his _Problems of
Species-formation_ (1903, p. 174), have dealt fully with the theory
of mutation, and, while appreciating the interesting observations
and experiments of De Bries, have rejected the theory he has built
on them. As I share their opinion, I may refer the reader who is
interested in these difficult problems to their works, and will
restrict myself here to the following observations. The chief weakness
of the theory of mutation of De Bries is on its logical side, in
his dogmatic distinction between species and variety, mutation and
variation. When he holds the constancy of species as a fundamental
"fact of observation," we can only say that this (relative) permanence
of species is very different in the different classes. In many
classes (for instance, insects, birds, many orchids and graminea) we
may examine thousands of specimens of a species without finding any
individual differences; in other classes (such as sponges, corals, in
the genera _rubus_ and _hieracium_) the variability is so great that
classifiers hesitate to draw up fixed species. The marked difference
between various forms of variability which De Bries alleges cannot
be carried through; the fluctuating variations (which he takes to be
unimportant) cannot be sharply distinguished from the abrupt mutations
(from which new species are supposed to result at a bound). De Bries's
mutations (which I distinguished in the _General Morphology_ as
"monstrous changes" from other kinds of variation) must not be confused
with the paleontological mutations of Waagen (1869) and Scott (1894)
which have the same name. The sudden and striking changes of habit
which De Bries observed only in one single species of _œnothera_
very rarely occur, and cannot be regarded as common beginnings of
the formation of new species. It is a curious freak of chance that
this species bears the name _œnothera Lamarckiana_; the views of
the great Lamarck on the powerful influence of functional adaptation
have not been refuted by De Bries. It must be carefully noted, in
fact, that De Bries is firmly convinced of the truth of Lamarck's
theory of descent, like all competent modern biologists. This must be
well understood, because recent metaphysicians see in the supposed
refutation of Darwinism the death of the whole theory of transformism
and evolution. When they appeal in this sense to its most virulent
opponents, Dennert, Driesch, and Fleischmann, we may remind them that
the curious sermons of these minor sophists are no longer noticed by
any competent and informed scientist.

Not only in the brilliant speculations of De Bries and Nägeli, but
also in many other botanical works that have lately attempted to
advance the theory of descent, we find a striking difference from
the prevailing views of zoologists in the treatment of a number of
general biological problems. This difference is, of course, not
due to a disproportion of ability in the two great and neighboring
camps of biology, but to the differences in the phenomena that we
observe in plant life on the one hand and animal life on the other.
It must be noted particularly that the organism of the higher animals
(including our own) is much more elaborately differentiated in its
various organs and much more exposed to our direct experience than
that of the higher plants. The chief properties and activities of our
muscles, skeleton, nerves, and sense-organs, are understood at once
in comparative anatomy and physiology. The study of the corresponding
phenomena in the bodies of the higher plants is much more difficult.
The features of the innumerable elementary organs in the cell-monarchy
of the animal body are much more intricate, yet at the same time much
more intelligible, than those of the cell-republic of the higher
plant-body. Thus the phylogeny of the plants encounters much greater
difficulties than that of the animals; the embryology of the former
says much less in detail than that of the latter. We can understand,
therefore, why the biogenetic law is not so generally recognized by
botanists as by zoologists. Paleontology, which provides such valuable
fossil material for many groups of the animal kingdom that we can
more or less correctly draw up their ancestral tree on the strength
of this, gives us very little for most groups of the plant kingdom.
On the other hand, the large and sharply demarcated plant-cell, with
its various organella, is much more valuable in connection with many
problems than the tiny animal-cell. For many physiological purposes,
in fact, the higher plant body is more accessible to exact physical
and chemical research than the higher animal body. The antithesis is
less in the kingdom of the protists, as the difference between animal
and vegetal life is mostly confined to difference of metabolism, and
finally disappears altogether in the province of the unicellular forms
of life. Hence, for a clear and impartial treatment of the great
problems of biology, and especially of phylogeny, it is imperative to
have a knowledge of both zoological and botanical investigation. The
two great founders of the theory of descent--Lamarck and Darwin--were
able to penetrate so deeply into the mysteries of organic life and its
development because they had extensive attainments both in botany and
zoology.

Of the various tendencies that have recently made their appearance
among zoologists and botanists in the discussion of the theory
of descent, we frequently find Neo-Lamarckism and Neo-Darwinism
distinguished as opposing schools. This opposition has no meaning
unless we understand by it the alternatives of transformism--with or
without the theory of selection. The one principle that distinguishes
Darwinism proper from the older Lamarckism is the struggle for
existence and the theory of selection based on it. It is quite wrong
to make the test an acceptance or rejection of progressive heredity.
Darwin was just as firmly convinced as Lamarck or myself of the great
importance of the inheritance of acquired characters, and particularly
of the inheritance of functional adaptations; he merely ascribed to it
a more restricted sphere of influence than Lamarck. Weismann, however,
denies progressive heredity altogether, and wants to trace everything
to "the omnipotence of natural selection." If this view of Weismann
and the theory of germ-plasm he has based on it are correct, he alone
has the honor of founding a totally new (and in his opinion very
fruitful) form of transformism. But it is quite wrong to describe this
Weismannism as Neo-Darwinism, as frequently happens in England. It is
just as wrong to call Nägeli, De Bries, and other modern biologists who
reject selection Neo-Lamarckists.

If the theory of descent is right, as all competent biologists now
admit, it puts on morphology the task of assigning approximately the
origin of each living form. It must endeavor to explain the actual
organization of each by its past, and to recognize the causes of its
modification in the series of its ancestors. I made the first attempt
to achieve this difficult task in founding stem-history or phylogeny
as an independent historical science in my "General Evolution" (in
the second volume of the _General Morphology_). With it I associated
as a second and equally sound part ontogeny; I understood by this the
whole science of the development of the individual, both embryology and
metamorphology. Ontogeny enjoys the privileges (especially in the way
of certainty) of a purely descriptive science, when it confines itself
to the faithful description of the directly observed facts, either the
embryonic processes in the womb or the later metamorphic processes.
The task of phylogeny is much more difficult, as it has to decipher
long-past processes by means of imperfect evidence, and has to use its
documents with the utmost prudence.

The three most valuable sources of evidence in phylogeny are
paleontology, comparative anatomy, and ontogeny. Paleontology seems
to be the most reliable source, as it gives us tangible facts in
the fossils which bear witness to the succession of species in the
long history of organic life. Unfortunately, our knowledge of the
fossils is very scanty and often very imperfect. Hence the numerous
gaps in its positive evidence have to be filled up by the results of
two other sciences, comparative anatomy and ontogeny. I have dealt
fully with this in my _Anthropogeny_. As I have also spoken of the
general features of these phyletic evidences in the sixteenth chapter
of the _History of Creation_, I need do no more here than repeat
that it is necessary to make equal and discriminating use of all
three classes of documents if we are to attain the aim of phylogeny
correctly. Unfortunately, this necessitates a thorough knowledge of
all three sciences, and this is very rare. Most embryologists neglect
paleontology, most paleontologists embryology, while comparative
anatomy, the most difficult part of morphology, involving most
extensive knowledge and sound judgment, is neglected by both. Besides
these three sources of phylogeny there is valuable proof afforded
by every branch of biology, especially by chorology, œcology,
physiology, and biochemistry.

Although there has been very extensive phylogenetic research during the
last thirty years, and it has yielded a number of interesting results,
many scientists still seem to look on them with a certain distrust;
some contest their scientific value altogether, and say that they are
nothing but airy and untenable speculations. This is especially the
case with many physiologists who look upon experiment as the only
exact method of investigation, and many embryologists who think their
sole task is description. In view of these sceptical strictures, we
may recall the history and the nature of geology. No one now questions
the great importance and the various uses of this science, although
in it there is no possibility of directly observing the historical
processes as a rule. No scientist now doubts that the three vast
successive formations of the Mesozoic Period--the Triassic, Jurassic,
and Cretaceous--have been formed from sea-deposits (lime, sandstone,
and clay), though no one was a witness to the actual formation; no one
doubts to-day that the fossil skeletons of fishes and reptiles which
we find in these groups are not mysterious freaks of nature, but the
remains of extinct fishes and reptiles that lived on the earth during
those millions of years long ago. And when comparative anatomy shows us
the genealogical connection of these related forms, and phylogeny (with
the aid of ontogeny) constructs their ancestral trees, their historical
hypotheses are just as sound and reliable as those of geology; the
only difference is that the latter are much simpler, and thus easier
to construct. Phylogeny and geology are, in the nature of the case,
_historical sciences_.

Hypotheses are necessary in phylogeny and geology, where the empirical
evidence is incomplete, as in every other historical science. It is no
detraction from the value of these to urge that they are sometimes weak
and have to be replaced by better and stronger ones. A weak hypothesis
is always better than none. We must, therefore, protest against the
foolish dread of hypotheses which is urged against our phylogenetic
methods by the representatives of the exact and descriptive sciences.
This shrinking from hypotheses often hides a defective knowledge of
other sciences, an incapacity for synthetic thought, and a feeble sense
of causality. The delusions into which it leads many scientists may be
seen from the fact that chemistry, for instance, is reckoned an "exact"
science; yet no chemist has ever seen the atoms and molecules of
compounds with which he is occupied daily, or the complicated relations
on the assumption of which the whole of modern structural chemistry
is based. All these hypotheses rest on inferences, not on direct
observation.

I have, from the first, insisted on the close causal connection between
ontogeny and phylogeny, ever since I distinguished these two parts of
biogeny in the fifth book of the _General Morphology_. I also laid
stress on the mechanical character of these sciences, and endeavored
to give a physiological explanation of their morphological phenomena.
Until then embryology had been regarded as a purely descriptive
science. Carl Ernst Baer, who had provided a solid foundation for it
in his classic _Animal Embryology_ (1828), was convinced that all the
phenomena of individual development might be reduced to the laws of
growth; but he was quite unconscious of the real direction of this
growth, its "purposiveness," the real causes of construction. The
distinguished Würtzburg anatomist, Albert Kölliker, whose _Manual of
Human Embryology_ (1859) gave the first comprehensive treatment of the
science from the cellular point of view, adhered, even in the fourth
edition (1884), to the opinion that "the laws of the development of
the organism are still completely unknown." In opposition to this
generally received opinion, I endeavored, in 1866, to prove that Darwin
had, by his improvement of the theory of descent, not only solved
the phylogenetic problem of the origin of species, but, at the same
time, given us the key to open the closed doors of embryology, and to
learn the causes of the ontogenetic processes as well. I formulated
this view in the twentieth chapter of the _General Morphology_, in
forty-four theses, of which I will quote only the following three: 1.
The development of organisms is a physiological process, depending on
mechanical causes, or physico-chemical movements. 40. Ontogenesis, or
the development of the organic individual, is directly determined by
phylogenesis, or the evolution of the organic stem (_phylon_) to which
it belongs. 41. Ontogenesis is a brief and rapid recapitulation of
phylogenesis, determined by the physiological functions of heredity and
adaptation. The pith of my biogenetic principle is expressed in these
and the remaining theses on the causal nexus of biontic and phyletic
development. At the same time I make it quite clear that I reduce the
physical process of ontogenesis, and also phylogenesis, to a pure
mechanics of the plasm (in the sense of the critical philosophy).

The comprehensive fundamental law of organic development was briefly
formulated by me in the fifth book of the _General Morphology_ and in
the tenth chapter of the _History of Creation_ (developed more fully
in the fourteenth chapter of the tenth edition, 1902). I afterwards
sought to establish it securely in two different ways. In the first
place, I proved in my _Studies of the Gastræa Theory_ (1872-1877)
that in all the tissue-animals, from the lowest sponges and polyps to
the highest articulata and vertebrates, the multicellular organism
develops from the same primitive embryonic form (the _gastrula_),
and that this is the ontogenetic repetition, in virtue of heredity,
of a corresponding stem-form (the _gastræa_). In the second place, I
made the first attempt in my _Anthropogeny_ (1874) to illustrate this
recapitulation theory from the instance of our own human organism, by
trying to explain the complex process of individual development, for
the whole frame and every single part of it, by causal connection with
the stem-history of our animal ancestors. In the latest edition of this
monistic "ontogeny of man" I gave numbers of illustrations (thirty
plates and five hundred engravings) of these intricate structures,
and endeavored to make the subject still plainer by the addition of
sixty genetic tables. I may refer the reader to this work,[10] and
not dwell any further here on the biogenetic law, especially as one
of my pupils, Heinrich Schmidt (of Jena), has recently described its
biological significance and its earlier history and present position in
a very clear and reliable little work (_Haeckel's Biogenetic Law and
its Critics_). I will only add a word or two on the struggle that has
taken place for thirty years over the complete or partial recognition
of the biogenetic law, its empirical establishment, and its philosophic
application.

In the very name, "fundamental law of biogeny," which I have given to
my recapitulation theory, I claim that it is universal. Every organism,
from the unicellular protists to the cryptogams and cœlenteria, and
from these up to the flowering plants and vertebrates, reproduces in
its individual development, in virtue of certain hereditary processes,
a part of its ancestral history. The very word "recapitulation"
implies a partial and abbreviated repetition of the course of the
original phyletic development, determined by the "laws of heredity
and adaptation." Heredity brings about the reproduction of certain
evolutionary features; adaptation causes a modification of them by
the conditions of the environment--a condensation, disturbance, or
falsification. Hence I insisted from the first that the biogenetic law
consists of two parts, one positive and palingenetic and the other
restrictively negative and cenogenetic. _Palingenesis_ reproduces a
part of the original history of the stem; _cenogenesis_ disturbs or
alters this picture in consequence of subsequent modifications of the
original course of development. This distinction is most important, and
cannot be too often repeated in view of the persistent misunderstanding
of my opponents. It is overlooked by those who (like Plate and
Steinmann) grant it only a partial validity, and by those who reject
it altogether (like Keibel and Hensen). The embryologist Keibel is the
most curious of these, as he has himself afforded a good many proofs
of the biogenetic law in his careful descriptive-embryological works.
But he has so little mastered it that he has never understood the
distinction between palingenesis and cenogenesis.

It is especially unfortunate that one of our most distinguished
embryologists, Oscar Hertwig, of Berlin, who provided a good deal of
evidence in favor of the biogenetic law thirty years ago, has lately
joined the opponents of it. His supposed "correction" or modification
of it is, as Keibel has rightly said, a complete abandonment of it.
Heinrich Schmidt has partly explained the causes of this change
in his work on the biogenetic law. They are not unconnected with
the psychological metamorphosis which Oscar Hertwig has undergone
at Berlin. In the discourse on "The Development of Biology in the
Nineteenth Century," which he delivered at the scientific congress at
Aachen in 1900, he openly accepted the dualist principles of vitalism
(although he says they are "just as unreliable as the chemico-physical
conception of the opposing mechanical school"). The views which he has
lately advanced on the worthlessness of Darwinism and the unreliability
of phylogenetic hypotheses are diametrically opposed to the opinions
he represented at Jena twenty-five years ago, and to those which his
brother, Richard Hertwig, of Munich, has consistently maintained in his
admirable _Manual of Zoology_.

In opposition to the mechanical ontogeny which I formulated in 1866
and embodied in the biogenetic law, a number of other tendencies
in embryology afterwards appeared, and, with the common title of
"mechanical embryology," branched out in every direction. The chief of
these to attract attention thirty years ago were the pseudo-mechanical
theories of Wilhelm His, who has rendered great service to ontogeny
by his accurate descriptions and faithful illustrations of
vertebrate-embryos, but who has no idea of comparative morphology,
and so has framed the most extraordinary theories about the nature
of organic development. In his _Study of the First Sketch of the
Vertebrate-body_ (1868), and many later works, His endeavored to
explain the complicated ontogenetic phenomena on direct and simple
physical lines by reducing them to elasticity, bending, folding of the
embryonic layers, etc., while explicitly rejecting the phylogenetic
method; he says that this is "a mere by-way, and quite unnecessary for
the explanation of the ontogenetic facts (as direct consequences of
physiological principles of development)." As a matter of fact, nature
rather plays the part of an ingenious tailor in His's pseudo-mechanical
and tectogenetic speculations, as I have shown in the third chapter of
the _Anthropogeny_. Hence they have been humorously called the "tailor
theory." However, they misled a few embryologists by opening the way
to a direct and purely mechanical explanation of the complex embryonic
phenomena. Although they were at first much admired, and immediately
afterwards abandoned, they have found a number of supporters lately in
various branches of embryology.

The great success that modern experimental physiology achieved by its
extensive employment of physical and chemical experiments inspired a
hope of attaining similar results in embryology by means of the same
"exact" methods. But the application of them in this science is only
possible to a slight extent on account of the great complexity of the
historical processes and the impossibility of "exactly" determining
historical matters. This is true of both branches of evolution,
individual and phyletic. Experiments on the origin of species have
very little value, as I said before; and this is generally true of
embryological experiments also. However, the latter, especially
careful experiments on the first stages of ontogenesis, have yielded
some interesting results, particularly in regard to the physiology
and pathology of the embryo at the earliest stages of development.
The _Archiv für Entwickelungsmechanik_, which is edited by the chief
representative of this school, Wilhelm Roux, contains, besides these
valuable inquiries, a good number of ontogenetic articles, which partly
rely on and partly ignore the biogenetic law.

Psychology and biogeny have been up to the present regarded as the
most difficult branches of biology for monistic explanation, and the
strongest supports of dualistic vitalism. Both departments become
accessible to monism and a mechanico-causal explanation by means
of the biogenetic law. The close correlation which it establishes
between individual and phyletic development, and which depends on the
interaction of heredity and adaptation, makes it possible to explain
both. In regard to the first, I formulated the following principle
thirty years ago in my first study of the gastræa theory: "Phylogenesis
is the mechanical cause of ontogenesis." This single principle clearly
expresses the essence of our monistic conception of organic development:

 In the future every student will have to declare himself for or
 against this principle, if in biogeny he is not content with a mere
 admiration of the wonderful phenomena, but desires to understand
 their significance. The principle also makes clear the wide gulf
 that separates the older teleological and dualistic morphology from
 the modern mechanical and monistic science. If the physiological
 functions of heredity and adaptation are proved to be the sole causes
 of organic construction, every kind of teleology, and of dualistic
 and metaphysical explanation, is excluded from the province of
 biogeny. The irreconcilable opposition between the leading principles
 of the two is clear. Either there is or is not a direct and causal
 connection between ontogeny and phylogeny. Either ontogenesis is a
 brief compendium of phylogenesis or it is not. Either epigenesis and
 descent--or pre-formation and creation.

In repeating these principles here, I would lay stress particularly on
the fact that, in my opinion, our "mechanical biogeny" is one of the
strongest supports of the monistic philosophy.




XVII

THE VALUE OF LIFE

 Changes of life--Aim of life--Progress of life--Historic
 aims--Historic waves--Value of life in classes and races of
 men--Psychology of uncivilized races--Savages--Barbarians--Civilized
 nations--Educated nations--Three stages of development (lower,
 middle, and higher) in each of the four classes--Individual and
 social value of civilized life in the five sections of nutrition,
 reproduction, movement, sensation, and mental life--Estimate of human
 life.


The value of human life is seen by us to-day, now that evolution is
established, in quite a different light from fifty years ago. We are
now accustomed to regard man as a natural being, the most highly
developed natural being that we know. The same "eternal iron laws"
that rule the evolution of the whole cosmos control our own life.
Monism teaches that the universe really deserves its name, and is an
all-embracing unified whole--whether we call it God or Nature. Monistic
anthropology has now established the fact that man is but a tiny part
of this vast whole, a placental mammal, developed from a branch of
the order of primates in the later Tertiary Period. Hence, before we
seek to estimate the value of man's life, we will cast a glance at the
significance of organic life generally.

An impartial survey of the history of organic life on our planet
teaches, first of all, that it is a process of constant change.
Millions of animals and plants die every second, while other millions
replace them; every individual has his definite period of life,
whether it lives only a few hours, like the one-day fly or the
infusorium, or, like the Wellingtonia, the dragon-tree of Orotava, and
many other giant trees, lives for thousands of years. Even the species,
the collection of like individuals, is just as transitory, and so are
the orders and classes that embrace numbers of species of animals and
plants. Most species are confined to a single period of the organic
history of the earth; few species or genera pass unchanged through
several periods, and not a single one has lived in all the periods.
Phylogeny, taking its stand on the facts of paleontology, teaches
unequivocally that every specific living form has only existed a longer
or shorter period in the course of the many (more than a hundred)
million years which make up the history of organic life.

Every living being is an end to itself. On this point all unprejudiced
thinkers are agreed, whether, like the teleologist, they believe in an
entelechy or dominant as regulator of the vital mechanism, or whether
they explain the origin of each special living form mechanically by
selection and epigenesis. The older anthropistic idea, that animals
and plants were created for man's use, and that the relations of
organisms to each other were generally regulated by creative design,
is no longer accepted in scientific circles. But it is just as true of
the species as of the individual that it lives for itself, and looks
above all to self-maintenance. Its existence and "end" are transitory.
The progressive development of classes and stems leads slowly but
surely to the formation of new species. Every special form of life--the
individual as well as the species--is therefore merely a biological
episode, a passing phenomenal form in the constant change of life. Man
is no exception. "Nothing is constant but change," said the old maxim.

The historical succession of species and classes is, both in the
animal and the plant kingdom, accompanied by a slow and steady
progress in organization. This is directly and positively taught by
paleontology; its creation-medals, the fossils, are unequivocal and
irrefutable witnesses to this phylogenetic advance. I have dealt with
the subject in my _History of Creation_, and at the same time shown
that both the progressive improvement and the increasing variety of
the species can be explained mechanically as necessary consequences of
selection. There was no need of a conscious Creator or a transcendental
purposiveness to effect this. Scientific and thorough proof of this
will be found in the three volumes of my _Systematic Phylogeny_ (1894).
I need only refer briefly to the two conspicuous examples we have in
the stem-history of the tissue-plants and that of the vertebrates. Of
the metaphyta the ferns are the chief groups in the Paleozoic, the
gymnosperms in the Mesozoic, and the angiosperms in the Cenozoic age.
Of the vertebrates only fishes are found in the Silurian age, dipneusta
only begin in the Devonian, and the first mammals are in the Triassic.

A number of false teleological conclusions have been drawn from these
facts of progressive modification of forms, as they are given in
paleontology. The latest and most developed form of each stem was
taken to be the preconceived aim of the series, and its imperfect
predecessors were conceived as preparatory stages to the attainment
of this aim. It was like the conduct of many historians, who, when
a particular race or state has reached a high rank in civilization
as a result of its natural endowments and favorable conditions of
development, hail it as a "chosen people," and regard its imperfect
earlier condition as a deliberately conceived preparatory stage.
In point of fact, these evolutionary stages were bound to proceed
according as the internal structure (given by heredity) and the outer
conditions (provoking adaptation) determined. We cannot admit any
conscious direction to a certain end, either in the form of theistic
predestination or pantheistic finality. For this we must substitute a
simple mechanical causality in the sense of psycho-mechanical monism or
hylozoism.

Although the stem-history of plants and animals, like the history of
humanity, shows a progressive advance taken as a whole, we find a
good deal of vacillation in detail. These historical waves are wholly
irregular; in periods of decay the hollows of the waves often persist
for a long time, and are then succeeded by a fresh rise to the crest
of another wave. New and rapidly advancing groups come to take the
place of the old decaying groups, bringing with them a higher stage
of organization. Thus, for instance, the ferns of to-day are only a
feeble survival of the huge and varied pteridophyta that formed the
most conspicuous part of the paleozoic forests in the Devonian and
Carboniferous periods; they were ousted in the Secondary Period by
their gymnosperm descendants (cycadea and conifers), and these, again,
in the Tertiary Period by the angiosperm flowering plants. So among the
terrestrial reptiles the modern tortoises, serpents, crocodiles, and
lizards are only a feeble remnant of the enormous reptile-fauna that
dominated the Secondary Period, the colossal dinosauri, pterosauri,
ichtyosauri, and plesiosauri. They were replaced in the Tertiary
Period by the smaller but more powerful mammals. In the history of
civilization the Middle Ages form a deep valley between the crests of
the waves of classical antiquity and modern culture.

These few examples suffice to show that the various classes and orders
of living things have a very different value when compared with each
other. In regard to their intrinsic aim, self-maintenance, it is true
that all organisms are on a level, but in their relations to other
living things and to nature as a whole they are of very unequal
value. Not only may larger animals and plants retain domination for a
long time in virtue of their special use or superior force and mass,
but small ones may prevail owing to their power of inflicting injury
(bacteria, fungi, parasites, etc.). In the same way the value of the
various races and nations is very unequal in human history. A small
country like Greece has almost dominated the mental life of Europe
for more than two thousand years in virtue of its superior culture.
On the other hand, the various tribes of American Indians have, it is
true, developed a partial civilization in some parts (Peru and Central
America); but, on the whole, they have proved incapable of advancing.

Though the great differences in the mental life and the civilization
of the higher and lower races are generally known, they are, as a
rule, undervalued, and so the value of life at the different levels is
falsely estimated. It is civilization and the fuller development of the
mind that makes civilization possible, that raise man so much above
the other animals, even his nearest animal relatives, the mammals. But
this is, as a rule, peculiar to the higher races, and is found only
in a very imperfect form or not at all among the lower. These lower
races (such as the Veddahs or Australian negroes) are psychologically
nearer to the mammals (apes or dogs) than to civilized Europeans; we
must, therefore, assign a totally different value to their lives. The
views on the subject of European nations which have large colonies in
the tropics, and have been in touch with the natives for centuries,
are very realistic, and quite different from the ideas that prevail in
Germany. Our idealistic notions, strictly regulated by our academic
wisdom and forced by our metaphysicians into the system of their
abstract ideal-man, do not at all tally with the facts. Hence we can
explain many of the errors of the idealistic philosophy and many of
the practical mistakes that have been made in the recently acquired
German colonies; these would have been avoided if we had had a better
knowledge of the low psychic life of the natives (_cf._ the writings of
Gobineau and Lubbock).

The grave errors that have been maintained in psychology for centuries
are mostly due to a neglect of the comparative and genetic methods and
the narrow employment of self-observation, or the introspective method;
they are also partly due to the fact that metaphysicians generally make
their own highly developed mind--a scientifically trained reason--the
starting-point of their inquiry, and regard this as representative of
the human mind in general, and thus build up their ideal scheme. The
gulf between this thoughtful mind of civilized man and the thoughtless
animal soul of the savage is enormous--greater than the gulf that
separates the latter from the soul of the dog. Kant would have avoided
many of the defects of his critical philosophy, and would not have
formulated some of his powerful dogmas (such as the immortality of the
soul, or the categorical imperative) if he had made a thorough and
comparative study of the lower soul of the savage, and phylogenetically
deduced the soul of civilized man therefrom.

The extreme importance of this comparison has only been fully
appreciated of late years (by Lubbock, Romanes, etc.). Fritz Schultze
(of Dresden) made the first valuable attempt in his interesting
_Psychology of the Savage_ (1900) to give us an "evolutionary
psychological description of the savage in respect of intelligence,
æsthetics, ethics, and religion." At the same time, he gives us "a
history of the natural creation of the human imagination, will, and
faith." The first book of this important work deals with thought, the
second with will, and the third with the religious ideas of the savage,
or "the story of the natural evolution of religion" (fetichism,
animism, worship of the heavenly bodies). In an appendix to the second
book the author deals with the difficult problems of evolutionary
ethics, supporting himself by the authority of the great work of
Alexander Sutherland, _The Origin and Growth of the Moral Instinct_
(1898). Sutherland divides humanity, in regard to the various stages of
civilization and mental development (not according to racial affinity),
into four great classes: 1, Savages; 2, barbarians; 3, civilized
races; 4, educated races. As this classification of Sutherland's not
only enables us to take a good survey of the various forms of mental
development, but is also very useful in connection with the question of
the value of life at the different stages, I will briefly reproduce the
chief points of his characterization of the four classes.

I. SAVAGES.--Their food consists of wild natural products (the fruits
and roots of plants, and wild animals of all kinds). Most of them are,
therefore, fishers or hunters. They are ignorant of agriculture and the
breeding of cattle. They live isolated lives in families or scattered
in small groups, and have no fixed home. The lowest and oldest savages
come very close to the anthropoid apes from which they have descended,
in bodily structure and habits. We may distinguish three orders in this
class--the lower, middle, and higher savages.

_A._ Lower savages, approaching nearest to the ape, pygmies of
small stature, four to four and a half feet high (rarely four and
three-quarters); the women sometimes only three to three and a half
feet. They are woolly haired and flat-nosed, of a black or dark brown
color, with pointed belly, thin and short legs. They have no homes, and
live in forests and caverns, and partly on trees; wander about in small
families of ten to forty persons; quite naked, or with just a trace of
some primitive garment. Of the lower races now living we must put in
this class the Veddahs of Ceylon, the Semangs of the Malay Peninsula,
the Negritos of the Philippines, the Andaman Islanders, the Kimos of
Madagascar, the Akkas of Guinea, and the Bushmen of South Africa. Other
scattered remnants of these ancient negroid dwarfs, which approach
closely to the anthropoid apes, still live in various parts of the
primitive forests of the Sunda Islands (Borneo, Sumatra, Celebes).

The value of the life of these lower savages is like that of the
anthropoid apes, or very little higher. All recent travellers who have
carefully observed them in their native lands, and studied their bodily
structure and psychic life, agree in this opinion. Compare the thorough
treatment of the Veddahs of Ceylon in the work of the brothers Sarasin
(of which I have given a summary in my _Travels in Ceylon_). Their only
interests are food and reproduction, in the same simple form in which
we find these among the anthropoid apes (_cf._ chapters xv. and xxiii.
of my _Anthropogeny_). Our own ancestors were probably much the same
ten thousand or more years ago. On the strength of fossil remains of
Pleistocene men Julius Kollmann has shown it to be very probable that
similar dwarf races (with an average height of four and a half feet)
inhabited Europe at that time.

_B._ Middle savages, somewhat larger and less apelike than the
preceding, averaging five to five and a half feet in height. Their
homes are rock caverns and shelters from the wind and rain. Though
they have shirts and other rudiments of clothing, both sexes generally
go naked; they have primitive weapons of wood and stone and rudely
fashioned boats, wander in troops of fifty to two hundred, and have
no social organization; certain races, however, have laws. To this
group belong the Australian negroes and Tasmanians, the Ainos of
Japan, the Hottentots, Fuegians, Macas, and some of the forest races of
Brazil. The value of their life is very little superior to that of the
preceding order.

_C._ Higher savages, mostly of average human height (smaller in colder
regions), having always simple dwellings (generally of skins or the
bark of trees). They have always primitive clothing, and good weapons
of stone, bronze, or copper. They wander in troops of one hundred to
five hundred, led by prominent but not ruling princes, and exhibiting
rudimentary differences of rank. The method of life is determined
by hereditary customs. To this group belong many of the primitive
inhabitants of India (Todas, Nagas, Curumbas, etc.), the Nicobar
Islanders, the Samoyeds, and Kamtschadals; in Africa, the negroes of
Damara; and most of the Indian tribes of North and South America. Their
life is higher than that of the pithecoid lower and middle savages, but
less than that of the barbarians.

II. BARBARIANS OR SEMI-SAVAGES.--The greater part of their food
consists of natural products, which they secure with some foresight;
hence they have developed agriculture and pasture to a greater or less
extent. The division of labor is slight, each family supplying its
own wants. As a rule, a stock of food is provided for the whole year.
As a result of this, art begins to develop. They have generally fixed
dwellings.

_A._ Lower Barbarians. Dwellings: Simple huts, generally grouped into
villages and surrounded with plantations. Clothing worn regularly, but
very simple: the men often naked in hot climates or with shirt. Pottery
and cooking utensils, tools of stone, wood, or bone. Rudiments of
commerce by exchange. Groups of one thousand to five thousand persons
able to form larger communities; distinctions of rank and warfare.
Princes rule according to traditional laws. Of this group we have
in Asia many of the aboriginal inhabitants of India (Mundas, Khonds,
Paharias, Bheels, etc.), the Dyaks of Borneo, the Battaks of Sumatra,
Tunguses, Kirgises, etc.; in Africa the Kaffirs, Bechuanas, and
Basutos; in Australasia the aborigines of New Guinea, New Caledonia,
New Hebrides, New Zealand, etc.; and in America the Iroquois and
Thlinkets, and the inhabitants of Nicaragua and Guatemala.

_B._ Middle barbarians. Dwellings good and durable, generally of wood,
roofed with cane or straw, forming fine towns. Clothing general, though
nudity is not considered immoral. Pottery, weaving, and metal-work
pretty well developed. Commerce in regular markets, with the use of
money. States ruled by kings in accordance with traditional laws,
fixed distinctions of rank, communities up to one hundred thousand
persons. To these belong in Asia the Calmucks; in Africa many negro
races (Ashantis, Fantis, Fellahs, Shilluks, Mombuttus, Owampos, etc.);
in Polynesia the inhabitants of the Fiji, Tonga, Samoa, and Markesas
islands. In Europe the Lapps belonged to this class two hundred years
ago, the ancient Germans two thousand years ago, the Romans before
Numa, and the Greeks of the Homeric period.

_C._ Higher barbarians. Dwellings, usually solid stone buildings.
Clothing obligatory, weaving habitual occupation of the women,
metal-work far advanced, tools generally of iron. Restricted commerce,
with minted money, no rudder-ships. Crude judicature in fixed courts;
rudimentary writing. Masses of people, with progressive division of
labor and hereditary distinctions of rank, sometimes reaching half a
million souls, under an autonomous ruler. To this class belong in Asia
most of the Malays (in the large Sunda Islands and the peninsula of
Malacca), and the nomadic races of Tartars, Arabs, etc.; in Polynesia
the islanders of Tahiti and Hawaii; in Africa the Somalis and
Abyssinians, and the inhabitants of Zanzibar and Madagascar. Of the
historic peoples of antiquity we have the Greeks of the time of Solon,
the Romans at the beginning of the republic, the Jews under the Judges,
the Anglo-Saxons of the Heptarchy, and the Mexicans and Peruvians at
the time of the Spanish invasion.

III. CIVILIZED RACES.--Food and complex vital needs are easily
satisfied on account of the advanced division of labor and improvement
of instruments. Art and science are consequently developed more and
more. The increasing specialization brings about a great elaboration
of individual functions, and at the same time a great strengthening of
the whole body politic, as there is complete mutual dependence. The
citizens see that they must submit to the laws of the state.

_A._ Lower civilized races. Towns with stone walls; vast architectural
works in stone; use of the plough in agriculture. War is intrusted to
a particular class. Writing firmly established, primitive law-books,
fixed courts. Literature begins to develop. To this group belong
in Asia the inhabitants of Thibet, Bhutan, Nepaul, Laos, Annam,
Korea, Manchuria, and the settled Arabs and Turcomans; in Africa the
Algerians, Tunisians, Moors, Kabyles, Tuaregs, etc. Of historical races
we have the ancient Egyptians, Phœnicians, Assyrians, Babylonians,
Carthaginians, the Greeks after Marathon, the Romans of the time of
Hannibal, and the English under the Norman kings.

_B._ Middle civilized races. Beautiful temples and palaces, built
of stone and brick. Windows come into use, and sailing-ships.
Commerce expands. Writing and written books are general; the literary
instruction of the young is attended to. Militarism is further
developed; so are legislation and advocacy. Of these we have in Asia
the Persians, Afghans, Birmans, and Siamese; in Europe the Finns and
Magyars of the eighteenth century. Of historical peoples we must count
among them the Greeks of the age of Pericles, the Romans of the later
republic, the Jews under the Macedonian rule, France under the first
Capets, and England under the Plantagenets.

_C._ Higher civilized races. Stone houses general; streets paved;
chimneys, canals, water and wind mills. Beginnings of scientific
navigation and warfare. Writing general, written books widely
distributed, literature esteemed. The highly centralized state embraces
communities of ten millions or more. Fixed and written codes of law
are officially promulgated and applied by courts to particular cases.
Numbers of government officials have settled rank. To this group belong
in Asia the Chinese, Japanese, and Hindoos; also the Turks and the
various republics of South America, etc. In history we have the Romans
of the empire, and the Italians, French, English, and Germans of the
fifteenth century.

IV. CULTIVATED RACES.--Food and other needs are artificially supplied
with the greatest ease and in abundance, human labor being replaced
by natural forces. The social organization grows and facilitates the
play of all the social forces, and man obtains a great freedom to
cultivate his mental and æsthetic qualities. Printing is in general
use, the education of the young one of the first duties. War becomes
less important; rank and fame depend less on military bravery than on
mental superiority. Legislation is influenced by representatives of the
people. Art and science are increasingly promoted by state aid.

Alexander Sutherland distinguishes three stages of development--the
lower, middle, and higher--in the fourth as well as in the preceding
classes. To the first stage he assigns "the leading nations of Europe
and their offshoots, such as the United States of North America."
For the second stage--middle cultured races--he gives a programme
that may be carried out in three or four hundred years' time, with
this definition: "All men are well fed and housed; war is universally
condemned, but breaks out now and again. Small armies and fleets of all
the nations co-operate as a sort of international police; commercial
and industrial life are directed according to the moral precepts of
sympathy; culture is general; crime and punishment rare." Of the third
and highest stage Sutherland merely says, "Too bold a subject for
prophecy, that may not come for one thousand to two thousand years
yet." This division seems to me too vague and unsatisfactory, in the
sense that it does not properly emphasize the civilization of the
nineteenth century in contrast with all preceding stages. It would
be better to distinguish _provisionally_ the following stages in
modern civilization: first, sixteenth to eighteenth century; second,
nineteenth century; and third, twentieth century and the future.

_A._ Lower cultured races (Europe, sixteenth to eighteenth century).
At the commencement of this period, the first half of the sixteenth
century, we notice the preparatory movements to the full growth of
mental life which was to achieve such great results in the following
periods: 1. The cosmic system of Copernicus (1543) maintained by
Galileo (1592). 2. The discovery of America by Columbus (1492) and of
the East Indies by Vasco da Gama (1498), the first circumnavigation
of the earth by Magellan (1520) and the evidence it afforded of the
rotundity of the earth. 3. The liberation of the mind of Europe
from the papal yoke by Martin Luther (1517) and the repulse of the
prevailing superstition by the spread of the Reformation. 4. The new
impulse to scientific investigation independently of scholasticism
and the Church and of the philosophy of Aristotle; the founding of
empirical science by Francis Bacon (1620). 5. The spread of scientific
knowledge by the press (Gutenberg, 1450) and wood-engraving. The way
was prepared for modern civilization by these and other advances in the
sixteenth century, and it quickly arose above the barbaric level of the
Middle Ages. However, it was confined at first within narrow limits, as
the reactionary civilization of the Middle Ages was still powerful in
political and social life, and the struggle against superstition and
unreason made slow progress. The French Revolution (1792) at last gave
a great impetus in practical directions.

_B._ Middle cultured races. This name may be given to the leading
nations of Europe and North America in the nineteenth century. We may
illustrate in the following achievements the great advance which this
"century of science" made as compared with all preceding ages: 1.
Deepening, experimental grounding, and general spread of a knowledge
of nature; independent establishment of many new branches of science;
founding of the cell-theory (1838), the law of energy (1845), and the
theory of evolution (1859). 2. Practical and comprehensive application
of this theoretical science to all branches of art and industry.
Especially 3. The overcoming of time and space by the extraordinary
speed of transit (steamboats, railways, telegraphs, electrotechnics).
4. Construction of the monistic and realistic philosophy, in opposition
to the prevailing dualistic and mystical views. 5. Increasing influence
of rational scientific instruction and abandonment of the religious
fiction of the Churches. 6. Increasing self-consciousness of the
nations on account of having a share in government and legislation;
extinction of the belief in the divine right of rulers. New distinction
of classes. However, these great advances, to which we children of the
nineteenth century may point with pride, are far from being universal;
they are struggling daily with reactionary views and powers in Church
and state, with militarism, and with ancient and venerable immorality
of every kind.

_C._ The higher culture which we are just beginning to glimpse will set
itself the task of creating as happy and contented a life as possible
for all men. A perfect ethic, free from all religious dogma and based
on a clear knowledge of natural law, will be found in the golden rule,
"Love thy neighbor as thyself." Reason tells us that a perfect state
must provide the greatest possible happiness for every individual that
belongs to it. The adjustment of a rational balance between egoism and
altruism is the aim of our monistic ethics. Many barbaric customs that
are still regarded as necessary--war, duelling, ecclesiastical power,
etc.--will be abolished. Legal decisions will suffice to settle the
quarrels of nations, as they now do of individuals. The chief interest
of the state will be, not the formation of as strong a military force
as possible, but the best possible instruction of its young, with
special attention to art and science. The improvement of technical
methods, owing to new discoveries in physics and chemistry, will bring
greater satisfaction of our needs of life. The artificial production of
albumin will provide plenty of food for all. A rational reform of the
marriage relations will increase the happiness of family life.

The darker sides of modern life, of which we are all more or less
sensitive, have been laid bare by Max Nordau in his _Conventional Lies
of Civilization_. They will be greatly altered if reason is permitted
to have its way in practical life, and the present evil customs, based
on antiquated dogmas, are suppressed. But, in spite of all these
shades, the luminous features of modern civilization are so great that
we look to the future with hope and confidence. We need only glance
back half a century, and compare life to-day with what it was then,
in order to realize the progress made. If we regard the modern state
as an elaborate organism (a "social individual of the first order"),
and compare its citizens to the cells of a higher tissue-animal, the
difference between the state of to-day and the crudest family groups
of savages is not less than that between a higher metazoon (such as a
vertebrate) and a cœnobium of protozoa. The progressive division
of labor, on the one hand, and the centralization of society, on the
other, prepare the social body for higher functions than in isolation,
and proportionately increase the worth of its life. To see this more
clearly, let us compare the personal and the social value of life in
the five chief fields of vital activity--nutrition, reproduction,
movement, sensation, and mental life.

The first need of the individual organism, self-maintenance, is met in
a much more perfect manner in the modern state than it was formerly.
The savage is satisfied with the raw products of nature--with hunting,
fishing, and the gathering of roots and fruits. Agriculture and
pasturage come later. Many stages of barbarism and lower civilization
must be passed before the conditions of feeding, housing, and clothing
provide a secure and comfortable existence for man, and permit the
addition of æsthetic and intellectual interests to the indispensable
search for food.

The feeding and condition of the social body as a whole have been
improved by modern civilization, just as in the case of the individual.
The progress of chemistry and agriculture has enabled us to produce
food in larger quantities. The ease and rapidity of transfer allow it
to be distributed over the whole earth. Scientific medicine and hygiene
have discovered many means of diminishing the dangers of disease and
preventing its occurrence. By means of public baths, gymnasiums,
popular restaurants, public gardens, etc., greater care is taken of
the health of the community. The arrangement of modern houses and
their heating and lighting have been immensely improved. Modern social
politics strives more and more to extend these benefits of civilization
to the lower classes. Philanthropic societies are busy supplying the
material and spiritual wants of various classes of sufferers. It is
true there is still a broad margin for the improvement of the national
well-being. But, on the whole, it cannot be denied that the provision
of food in the modern state is an immense advance upon that of the
Middle Ages and of the barbaric period.

The great value of modern civilization and its vast progress beyond
the condition of the savage is seen in no branch of physiology so
conspicuously as in the wonderful process of reproduction and the
maintenance of the species. In most savages and barbarians the
satisfaction of their powerful sexual impulse is at the same low stage
as in the ape and other mammals. The woman is merely an object of
lust to the man, or even a slave without rights, bought and exchanged
like all other property. Improvement is slow and gradual in the value
of this property, until it reaches a high guarantee of permanency in
the formal marriage. The family life proves a source of higher and
finer enjoyment for both parties. The position of woman advances with
civilization; her rights obtain further recognition, and in addition to
sensual love the psychic relation of man and wife begins to develop.
The common concern for the proper care and education of the children,
which we find to an extent even in the case of many animals, leads
to the further development of family life and the founding of the
school. With the advent of a higher stage of civilization begins the
refinement of sexual love, which finds its highest satisfaction, not in
the momentary gratification of the sex-impulse, but in the spiritual
relation of the sexes and their constant and intimate intercourse. The
beautiful then unites with the good and the true to form a harmonious
trinity. Hence love has been for thousands of years the chief source
of the æsthetic uplifting of man in every respect; the arts--poetry,
music, painting, and sculpture--have drawn inexhaustively from this
source. However, for the individual civilized human being this
higher love is of value, not only because it satisfies the natural
and irresistible sex-impulse in its noblest form, but also because
the mutual influence of the sexes, their complementary qualities and
their common enjoyment of the highest ideal good, has a great effect
upon individual character. A good and happy marriage--which is not
very common to-day--ought to be regarded, both psychologically and
physiologically, as one of the most important ends of life by every
individual of the higher nations.

As a pure marriage is the best form of family life and the most solid
foundation of the state, its high social value is at once evident. The
attraction and mutual devotion of the sexes fulfils in the highest
degree the ethical golden rule--the balance of egoism and altruism. As
Fritz Schultze very truly says in his _Comparative Psychology_

 We must not seek the causes of this altruism in the transcendental
 region of the supernatural, or in any metaphysical abstraction,
 but must go back to the very real and natural qualities of the
 organic being--and then there can be no question that the organic
 sex-impulse, at once physical and psychical is the first and enduring
 source of all love, however spiritual, and of all real ethical and
 sympathetic feelings and the morality founded thereon. There are
 two primitive instincts in all organisms: that of self-maintenance
 and that of the maintenance of the species. The one is the strong
 impulse of egoism, the other the spring of altruism: from the one
 come all unfriendly and from the other all friendly feelings. Every
 being seeks first to nourish and protect itself in virtue of its
 instinct of self-maintenance. But soon the magic of the instinct for
 the maintenance of the species works in it; it feels the sex-impulse,
 and thinks it is only satisfying its egoistic lust in yielding to
 it. In this it is wrong; it is not really serving itself, but the
 whole, the species, the genus. The ardor of love burns in it; and
 however sensual this love is at first, the new feeling is undeniably
 a feeling of belonging to another and of mutual consideration,
 looking not only to itself, but to another; not only to its own good,
 but to that of another, and finding its own good only in that of the
 other. And though this feeling at first only unites the two parents,
 it enlarges when children enter into life, and is extended to them
 in the form of parental love. Thus, out of the sex-impulse of the
 maintenance of the species, with its strong physical and psychic
 roots, is developed the love of spouses, of parents, of children,
 and of neighbor. Disinterested egoism goes even to the extent of
 sacrificing its own life for its young; in this organic and natural
 family love, and in the sense of the family that comes of it, we find
 the roots of all sympathetic and really ethical altruistic feelings;
 from this it widens out to larger spheres. Hence, the family is
 rightly held to be the chief source of all real moral feeling and
 life, not only in the human, but also in the animal world.

The further ennoblement of family life in the advance of civilization
will give fresh proofs of the truth of this appreciation.

We now turn to consider the advantages that modern civilization offers
in the way of movement in contrast to the simple methods of locomotion
of the savage. We may point out first that the earliest men, like their
ancestors, the anthropoid apes, lived in trees, and only gradually
began to run on the ground. Some of the higher savages began to use
the horse for riding and to tame it. Many inhabitants of the coast or
islands began at an early period to make boats. Later the barbaric
tribes invented the wagon, and much later again streets were paved
and vehicles improved by civilized races. But the nineteenth century
brought the invaluable means of rapid and convenient travelling by
means of steamboats and railways. The whole problem of transit was
revolutionized, and in the last few decades further vast changes have
been made owing to the advance of electricity. Modern ideas of time
and space are quite different from those of our parents sixty years
ago, or our grandparents ninety years ago. In our expresses we cover
in an hour a stretch of country that the mail-coach took five times
and the foot-passenger ten times as long to cover. As the experiments
with the Berlin electric railway have lately shown, we can now travel
two hundred kilometres in an hour. The journey from Europe to India
now takes three weeks, whereas the earlier sailing-vessel took as
many months. The immense saving of time that we make is equivalent to
a lengthening of our own life. This applies also to the more rapid
transit provided by balloons, automobiles, bicycles, etc. It is easy
to estimate the value of these improvements; but it is only fully
appreciated by those who have lived long in an uncivilized country
without roads or among savages whose legs are their only means of
locomotion.

This progress in the means of transit is not less valuable socially
than personally. If we conceive the state as a unified organism of the
higher order, the development of its means of transit corresponds in
many ways to that of the circulation of the blood in the vertebrate
frame. The easy, rapid, and convenient transport of the means of
life from the centre to the most distant parts of the land, and the
corresponding development of the net-work of railways and steamboat
routes, are to a certain extent direct tests of the degree of
civilization. To this we must add the creation of a large number of
offices which provide steady employment and means of subsistence for
many thousands.

To compare the complex sensations of civilized man with the much
simpler ones of the savage we must consider first the functions of
the outer organs of sense and then the internal sense-processes in the
cortex of the brain. Fritz Schultze has pointed out in his _Psychology
of the Savage_, in regard to both sets of organs, that the savage is
a man of sense-life, the civilized human being a man of mind-life.
When we remember that our higher psychic functions (sensation, will,
presentation, and thought) are anatomically connected with the phronema
(the thought-organ in the cortex), and the inner sense-perception
with the central sensorium (in the sense-centres of the cortex), we
shall expect to find the latter more developed in the savage and the
former in civilized man. The external sense-action is more intense in
quantity, but weaker in quality, in the savage than in civilized man;
this is especially true of the finer and more complex sense-functions
which we call æsthetic sensations and regard as the source of art and
poetry. Most strongly developed of all in the savage is the power of
perceiving distant objects (sight, hearing, smell), as they warn him of
the dangers about him. It is just the reverse with the subjective and
proximate feelings that are excited by the immediate touch of objects
and are the special instruments of sensual enjoyment--taste, sex-sense,
touch, and feeling of temperature. But in both kinds of sense-action
the civilized man is far ahead of the savage in respect of the finer
shades of feeling and æsthetic education. Moreover, modern civilization
has provided man with various means of vastly increasing and improving
the natural power of his senses. We need only mention the fields of
knowledge that have been opened to us by the microscope and telescope,
the refined chemical methods of modern cooking, etc. The finer æsthetic
enjoyment which our advanced art affords--plastic art for the eye,
music for the ear, perfumery for the nose, cuisine for the tongue--is
generally unintelligible to the savage, although he can see much
farther, and hear and smell much more acutely, than civilized man. And
in the senses of near objects (taste, touch, temperature) the senses of
the savages are more coarse, and incapable of the fine gradations of
civilized man.

This more refined sense-life and the accompanying æsthetic enjoyment
have no less social than personal value. We have, in the first place,
the incalculable treasure of modern art and science, their promotion
by the state, and their embodiment in the training of the young. In
the future the higher races are likely to give more attention to this,
training the senses of children as well as their intelligence from the
earliest years, leading them to a closer observation of nature and
reproduction of its forms by drawing and painting. The art-sense must
also be fostered by the exhibition of models and by æsthetic exercises,
a larger place must be given to artistic education along with the
acquisition of real knowledge, and an appreciation of the beauties of
nature must be created by means of walks and travels. Then the children
of civilized races will have the inexhaustible sources of the finest
and noblest pleasures in life opened to them in good time.

The higher psychic activity that civilized man calls his "mental life,"
and that is so often regarded as a kind of miracle, is merely a higher
development of the psychic function we find at a lower level in the
savage, and is shared by him with the higher vertebrates. Comparative
psychology shows us, as I have explained in the seventh chapter of the
_Riddle_, the long scale of development, which leads from the simple
cell-soul of the protist up to the intelligence of man. I have already
dealt in various chapters with this point, and need not enlarge on
it any further to estimate the high personal value of mental life in
every civilized human being. It is enough to remind the reader of
the vast treasures of knowledge that lie open to every one of us at
the commencement of the twentieth century--treasures of which our
grandparents at the beginning of the last century had not the slightest
presentiment.

Just as the individual has experienced a great advance in the value
of his personal life by the higher culture of the nineteenth century,
so the modern state itself has benefited by it in many ways. The many
discoveries made in every branch of science and technical industry, the
great advance in commerce and industrial life, in art and science, were
bound to bring about a higher development of the whole mind of a modern
community. Never, in the whole of history, has true science risen to
such an astounding height as it has at the beginning of the twentieth
century. Never before did the human mind penetrate so deeply into the
darkest mysteries of nature, never did it rise so high to a sense of
the unity of nature and make such practical use of its knowledge. These
brilliant triumphs of modern civilization have, however, only been
made possible by the various forces co-operating in a vast division of
labor, and by the great nations utilizing their resources zealously for
the attainment of the common end.

But we are still far from the attainment of the ideal. The social
organization of our states is advanced only on one side; it is very
reactionary on other sides. Unfortunately, the words of Wallace which
I quoted in the _Riddle_ remain as true as ever. Our modern states
will only pass beyond this condition in the course of the twentieth
century if they adopt pure reason as their guide instead of faith and
traditional authority, and if they come at length to understand aright
"man's place in nature."

If we take a summary view of all that I have said on the increase in
the value of human life by the progress of civilization, there can be
no doubt that both the personal and the social value of life are now
far higher than they were in the days of our savage ancestors. Modern
life is infinitely rich in the high spiritual interests that attach
to the possession of advanced art and science. We live in peace and
comfort in orderly social and civic communities, which have every
care of person and property. Our personal life is a hundred times
finer, longer, and more valuable than that of the savage, because it
is a hundred times richer in interests, experiences, and pleasures.
It is true that within the limits of civilization the differences in
the value of life are enormous. The greater the differentiation of
conditions and classes in consequence of division of labor, the greater
become the differences between the educated and uneducated sections of
the community, and between their interests and needs, and, therefore,
the value of their lives. This difference is naturally most conspicuous
if we consider the leading minds and the greatest heights of the
culture of the century, and compare these with the average man and the
masses, which wander far below in the valley, treading their monotonous
and weary way in a more or less stupid condition.

The state thinks quite otherwise than the individual man does of the
personal worth of his life and that of his fellows. The modern state
often demands for its protection the military service of all its
citizens. In the eyes of our ministers of justice the value of life
is the same whether there be question of an embryo of seven months
or a new-born child (still without consciousness), an idiot or a
genius. This difference between the personal and the social estimate
of life runs through the whole of our moral principles. War is still
believed by highly civilized nations to be an unavoidable evil, just as
barbarians think of individual murder or blood-revenge; yet the murder
of masses for which the modern state uses its greatest resources is in
flagrant contradiction to the gentle doctrine of Christian charity
which it employs its priests to preach every Sunday with all solemnity.

The chief task of the modern state is to bring about a natural
harmony between the social and the personal estimate of human life.
For this purpose we need, above all, a thorough reform of education,
the administration of justice, and the social organization. Only
then can we get rid of that mediæval barbarism of which Wallace
speaks; to-day it finds expression triumphantly in our penal laws,
our caste-privileges, the scholastic nature of our education, and the
despotism of the Church.

For each individual organism the life of the individual is the first
aim and the standard of value. On this rests the universal struggle
for self-maintenance, which can be reduced in the inorganic world to
the physical law of inertia. To this subjective estimate of life is
opposed the objective, which proceeds on the value of the individual
to the outer world. This objective value increases as the organism
develops and presses into the general stream of life. The chief of
these relations are those that come of the division of labor among
individuals and their association in higher groups. This is equally
true of the cell-states which we call tissues and persons, of the
higher stocks of plants and animals, and of the herds and communities
of the higher animals and men. The more these develop by progressive
division of labor and the greater the mutual need of the differentiated
individuals, so much the higher rises the objective value of the life
of the latter for the whole, and so much the lower sinks the subjective
value of the individual. Hence arises a constant struggle between the
interests of individuals who follow their special life-aim and those of
the state, for which they have no value except as parts of the whole.




XVIII

MORALITY

 Dualistic ethics--The categorical imperative--Monistic ethics--Morals
 and adaptation--Variation and adaptation--Habit--Chemistry of
 habit--Trophic stimuli--Habit in inorganic bodies--Instincts--Social
 instincts--Instinct and morality--Right and duty--Morals and
 morality--The good and the bad--Morals and fashions--Sexual
 selection--Fashion and the feeling of shame--Fashion and
 reason--Ceremonies and cults--Mysteries and sacraments--Baptism--The
 Lord's Supper--Transubstantiation--The miracle of redemption--Papal
 sacraments--Marriage--Modern fashions--Honor--Phylogeny of morals.


The practical life of man is, like that of all the social higher
animals, ruled by impulses and customs which we describe as "moral."
The science of morality, ethics, is regarded by the dualists as a
mental science, and closely connected with religion on the one hand and
psychology on the other. During the nineteenth century this dualistic
view retained its popularity especially because the great authority
of Kant, with his dogma of the categorical imperative, seemed to have
given it a solid foundation, and because it agreed admirably with the
teaching of the Church. Monism, on the other hand, regards ethics as
a natural science, and starts from the principle that morality is not
supernatural in origin, but has been built up by adaptation of the
social mammals to the conditions of existence, and thus may be traced
eventually to physical laws. Hence modern biology sees no metaphysical
miracle in morality, but the action of physiological functions.

Our whole modern civilization clings to the erroneous ideas which
traditional morality, founded on revelation, and closely connected
with ecclesiastical teaching, has imposed upon it. Christianity has
taken over the ten commandments from Judaism, and blended them with a
mystical Platonism into a towering structure of ethics. Kant especially
lent support to it in recent years with his _Critique of Practical
Reason_, and his three central dogmas. The close connection of these
three dogmas with each other, and their positive influence on ethics,
were particularly important through Kant formulating the further dogma
of the categorical imperative.

The great authority which Kant's dualist philosophy obtained is largely
owing to the fact that he subordinated pure reason to practical reason.
The vague moral law for which Kant claimed absolute universality is
expressed in his categorical imperative as follows: "So act that the
maxim (or the subjective principle of your will) may at the same time
serve as a general law." I have shown in the nineteenth chapter of the
_Riddle_ that this categorical imperative is, like the thing in itself,
an outcome of dogmatic, not critical, principles. As Schopenhauer says:

 Kant's categorical imperative is generally quoted in our day under
 the more modest and convenient title of "the moral law." The daily
 writers of compendiums think they have founded the science of ethics
 when they appeal to this apparently innate "moral law," and then
 build on it that wordy and confused tissue of phrases with which
 they manage to make the simplest and clearest features of life
 unintelligible, without having ever seriously asked themselves
 whether there really is any such convenient code of morality written
 in our head, breast, or heart. This broad cushion is snatched from
 under morality when we prove that Kant's categorical imperative
 of the practical reason is _a wholly unjustified, baseless, and
 imaginative assumption_.

Kant's categorical imperative is a mere dogma, and, like his whole
theory of practical reason, rests on dogmatic and not critical grounds.
It is a fiction of faith, and directly opposed to the empirical
principles of pure reason.

The notion of duty, which the categorical imperative represents as
a vague _a priori_ law implanted in the human mind--a kind of moral
instinct--can, as a matter of fact, be traced to a long series of
phyletic modifications of the phronema of the cortex. Duty is a
social sense that has been evolved _a posteriori_ as a result of the
complicated relations of the egoism of individuals and the altruism of
the community. The sense of duty, or conscience, is the amenability of
the will to the feeling of obligation, which varies very considerably
in individuals.

A scientific study of the moral law, on the basis of physiology,
evolution, ethnography, and history, teaches us that its precepts
rest on biological grounds, and have been developed in a natural way.
The whole of our modern morality and social and juridical order have
evolved in the course of the nineteenth century out of the earlier
and lower conditions which we now generally regard as things of the
past. The social morality of the eighteenth century proceeded, in its
turn, from that of the seventeenth and sixteenth centuries, and still
further from that of the Middle Ages, with its despotism, fanaticism,
Inquisition, and witch trials. It is equally clear from modern
ethnography and the comparative psychology of races that the morality
of barbarous races has been evolved gradually from the lower social
rules of savage tribes, and that these differ only in degree, not in
kind, from the instincts of the apes and other social vertebrates. The
comparative psychology of the vertebrates shows, further, that the
social instincts of the mammals and birds have arisen from the lower
stages of the reptiles and amphibia, and these in turn from those
of the fishes and the lowest vertebrates. Finally, the phylogeny of
the vertebrates proves that this highly developed stem has advanced
through a long series of invertebrate ancestors (chordonia, vermalia,
gastræada) from the protists by a process of gradual modification.
We find, even among these unicellulars (first protophyta, then
protozoa), the important principle which lies at the base of morality,
association, or the formation of communities. The adaptation of the
united cell-individuals to each other and to the common environment is
the physiological foundation of the first traces of morality among the
protists. All the unicellulars that abandon their isolated eremitic
lives, and unite to form communities, are compelled to restrict
their natural egoism, and make concessions to altruism in the common
interest. Even in the globular cœnobia of volvox and magosphæra the
special form and movement and mode of reproduction are determined by
the compromise between the egoistic instincts of the individual cells
and the altruistic need of the community.

Morality, whether we take it in the narrower or broader sense, can
always be traced to the physiological function of adaptation, which
is closely connected through nutrition with the self-maintenance of
the organism. The change in the plasm which adaptation brings about is
always based on the chemical energy of metabolism (chapter ix.). Hence
it will be as well to have a clear idea of the nature of adaptation. I
defined it as follows in my _General Morphology_:

 Adaptation or variation is a general physiological function of
 organisms, closely connected with their radical function of
 nutrition. It expresses itself in the fact that every organism may
 be modified by the influence of the environment, and may acquire
 characters which were wanting in its ancestors. The causes of
 this variability are chiefly found in a material correlation
 between parts of the organism and the outer world. Variability or
 adaptability is not, therefore, a special organic function, but
 depends on the material, physico-chemical process of nutrition.

I have developed this conception of adaptation in the tenth chapter of
the _History of Creation_.

The nature of the adaptation and its relation to variation are often
conceived in different ways from that I have defined. Quite recently
Ludwig Plate has restricted the idea, and understood by adaptation only
variations that are _useful_ to the organism. He severely criticises
my broader definition, and calls it "a palpable error," suggesting
that I only retain it because I am not open to conviction. If I wanted
to return this grave charge, I might point to Plate's one-sided and
perverse treatment of my biogenetic law. Instead of doing this I will
only observe that I think the restriction of adaptation to useful
variations is untenable and misleading. There are in the life of man
and of other organisms thousands of habits and instincts that are
not useful, but either indifferent or injurious to the organism,
yet certainly come under the head of adaptation, are maintained by
heredity, and modify the form. We find adaptations of all sorts--partly
useful, partly indifferent, partly injurious (the result of education,
training, distortion, etc.)--in the life of man, and the domestic
animals and plants. I need only refer to the influence of fashion
and the school. Even the origin of the useless (and often injurious)
rudimentary organs depends on adaptation.

Habit is a second nature, says an old proverb. This is a profound
truth, the full appreciation of which came to us through Lamarck's
theory of descent. The formation of a habit consists in the frequent
repetition of one physiological act, and so is in principle reducible
to cumulative or functional adaptation. Through this frequent
repetition of one and the same act, which is closely connected with the
memory of the plasm, a permanent modification is caused, either in a
positive or a negative sense; _positively_ the organ is developed and
strengthened by exercise, _negatively_ it is atrophied or enfeebled
by disuse. When this accumulation of slight changes continues, the
effect of adaptation goes so far in time as to produce new organs
by progressive modification, or to cause actual organs to become
useless and rudimentary, and finally disappear, owing to regressive
metamorphosis.

When we make a careful study of the simpler processes of habit in the
lower organisms, we see that they depend, like all other adaptations,
on chemical changes in the plasm, and that these are provoked by
trophic stimuli--that is to say, by external action on the metabolism.
As Ostwald rightly says: "The most important function of organisms
is the conversion of the various chemical energies into each other.
The chemical energy that is taken into the organism as food is not
generally capable of being applied directly to its purposes, but needs
some further preparation. Every cell is a chemical laboratory, in
which the most varied reactions take place without fires and retorts.
The most frequently employed means in this is probably the catalytic
acceleration of the usable and the catalytic retardation of the useless
reactions. As a proof of this we have the regular presence of these
enzyma in all organisms." In this the greatest importance attaches to
memory, which I regard with Hering as a general property of living
substance, "in virtue of which certain processes in the living being
leave effects behind them that facilitate the repetition of the
processes." I agree with Ostwald that "the importance of this property
cannot be exaggerated. In its more general forms it effects adaptation
and heredity, in its highest development the conscious memory." While
the latter, and consciousness in general, reach the highest stage in
the mental life of civilized man, the adaptation of the monera remains
at the lowest stage. Among the latter the bacteria especially, which
have assumed the most varied and important relations to other organisms
in spite of the simplicity of their structure, show that this manifold
adaptation depends on the formation of habits in the plasm, and is
solely based on their chemical energy, or their invisible molecular
structure. Once more the monera form a connecting link between the
organic and inorganic; they fill up the deep gulf, from the point of
view of energy, that seems to yawn between "animated" organisms and
"lifeless" bodies.

According to the prevailing view, habit is a purely biological process,
but there are processes even in inorganic nature which come under this
head in the broader sense. Ostwald gives the following illustration:

 If we take two equal tubes of thin nitric acid and dissolve a little
 metallic copper in one of them, the liquid will acquire the power to
 dissolve a second piece of the same metal more quickly than the one
 that remains unchanged. The cause of this phenomenon--which may be
 observed in the same way with mercury or silver and nitric acid--is
 that the lower oxydes of nitrogen that are formed in dissolving the
 metal accelerate the action of the nitric acid catalytically on the
 fresh metal. The same effect is produced if you put part of these
 oxydes in the acid; it then acts much more rapidly than pure acid.
 The formation of a habit consists, therefore, in the production of a
 catalytic acceleration during the reaction.

We may not only compare inorganic habit with organic adaptation, which
we call habit or practice, but also with "imitation," which implies a
catalytic transfer of habits to socially united living beings.

By instincts were formerly understood, as a rule, the unconscious
impulses of animals which led to purposive actions, and it was
believed that every species of animal had special instincts implanted
in it by the Creator. Animals were thought, according to Descartes's
view, to be unconscious machines whose actions proceed with unvarying
constancy in the particular form that God had ordained. Although
this antiquated theory of instinct is still taught by many dualistic
metaphysicians and theologians, it has long since been demolished
by the monistic theory of evolution. Lamarck had observed that most
instincts are formed by habit and adaptation, and then transmitted by
heredity. Darwin and Romanes especially showed afterwards that these
inherited habits are subject to the same laws of variation as other
physiological functions. However, Weismann has recently taken great
pains in his _Lectures on the Theory of Descent_ (xxiii.) to refute
this idea, and in general the hypothesis of an inheritance of acquired
characters, because it will not harmonize with his theory of the
germ-plasm. Ernst Heinrich Ziegler, who has recently (1904) published
a subtle analysis of former and present ideas of instinct, agrees with
Weismann that "all instincts are due to selection, and that they have
their roots not in the practice of the individual life, but in the
variations of the germ." But where else can we find the cause of these
"germ-variations" except in the laws of direct and indirect adaptation?
In my opinion, it is just the reverse; the remarkable phenomena of
instinct yield a mass of evidence of progressive heredity, completely
in the sense of Lamarck and Darwin.

The great majority of organisms live social lives, and so are united by
the link of common interests. Of all the relations which determine the
existence of the species, the chief are those which bind the individual
to other individuals of the species. This is at once clear from the
laws of sexual propagation. Moreover, the association of individuals is
a great advantage in the struggle for existence. In the case of the
higher animals this association becomes particularly important, because
it is accompanied by an extensive division of labor. Then arises the
antithesis of the personal egoism and the communal altruism; and in
human societies the opposition of the two instincts is all the greater
when reason recognizes that each has a right to satisfaction. Social
habits become moral habits, and their laws are afterwards taught as
sacred duties, and form the basis of the juridical order.

The morals of nations, so rich in psychological and sociological
interest, are nothing more than social instincts, acquired by
adaptation, and passed on from generation to generation by heredity.
An attempt has been made to distinguish between the two kinds of habit
by describing the instincts of animals as constant vital functions
based on their physical organization, and the habits or morals of human
beings as mental powers maintained by a spiritual tradition. This
distinction has, however, been excluded by the modern physiological
teaching that men's morals are, like all their other psychic functions,
based physiologically on the organization of their brain. The habits
of the individual man, which have been formed by adaptation to his
personal conditions, become hereditary in his family; and these family
usages can no more be sharply distinguished from the general morals of
the community than these can be from the precepts of the Church and the
laws of the state.

When a certain habit is regarded by all the members of a community
as important, its cultivation favored and its breach punished, it is
raised to the position of a duty. This is true even in the case of the
herds of mammals (apes, gregarious carnivora, and ungulates) and the
flocks of social birds (hens, geese, ducks). The laws which have been
formed in these cases by the higher development of social instincts
are particularly striking and equivalent to those of savage tribes
when conspicuous individuals (old or strong males) have acquired a
leadership of the troop, and successfully insure the observance of
the proper habits or duties. Many of these organized bands are in
some respects higher than the savages at the lowest stages who live
in isolated families, or only form loose temporary associations of a
few families. The great progress made by comparative psychology and
ethnology, and historical and prehistorical research, in the second
half of the nineteenth century, confirms us in the conviction that a
long scale of intermediate stages joins the rudiments of law in the
social primates and other mammals to the sense of law in the lower
savage, and this again to that of the barbarian and the civilized human
being--right up to the science of law in modern Europe.

Like civil laws, the commands of religion come originally from the
morals of the savage, and eventually from the social instincts of
the primates. The important province of mental life to which we give
the vague name of religion was developed at an early stage among the
prehistoric races from whom we all descend. When we study its origin
from the point of view of empirical psychology and monistic evolution,
we find that religion has arisen polyphyletically from different
sources--ancestor worship, the desire of personal immortality, the
craving for a causal explanation of phenomena, superstition of various
kinds, the strengthening of the moral law by the authority of a divine
law-giver, etc. According as the imagination of the savage or the
barbarian followed one or other of these lines it raised up hundreds
of religious forms. Only a few of them survived in the struggle for
existence, and acquired (at least outwardly) dominion over the modern
mind. But as independent and impartial science advances in our time,
religion is purified of superstition and turns more and more to
morality.

The obedience to the "divine commands" which religion demands of
its followers is often transferred by human society to rules that
have arisen from social customs of subordinate kinds. Thus we get
the familiar confusion of manners and morals, of conventional outer
deportment and real inner morality. The ideas of good and bad, morality
and immorality, are subjected to arbitrary definitions. In this a
great part is played by the moral pressure which is exercised by
conventional ideas in the social body on the conduct and minds of its
members. However clearly and rationally the individual thinks about the
important questions of practical life, he has to yield to the tyranny
of traditional and often quite irrational customs. As a matter of fact,
both in life and in the nature of the case practical reason does take
that precedence of pure reason which Kant claimed.

The tyranny of custom in practical life does not depend merely on the
authority of social usage, but also on the power of selection. Just as
natural selection insures the relative constancy of the specific form
in the origin of the animal and plant species, so it has a powerful
effect on the origin of morals and customs. An important factor in this
is mimetic adaptation, or mimicry, the aping or imitating of certain
forms or fashions by various classes of animals. This is unconscious in
the case of many orders of insects, butterflies, beetles, hymenoptera,
etc. When insects of a certain family come to resemble in their outer
form and color and design those of another family, they obtain the
protection or other advantages which these particular characters give
in the struggle for life. Darwin, Wallace, Weismann, Fritz Müller,
Bates, and others, have shown in numbers of instances how the origin
of these deceptive resemblances can be traced to natural selection,
and how important they are in the formation of the species. But many
customs and usages in human life arise in just the same way, partly by
conscious and partly by unconscious imitation. Of these the varying
external forms which we call "fashions" have a most important influence
in practical life. The phrase "fashion-ape," when used in a scientific
sense, is not merely an expression of contempt, but has also a profound
meaning; it correctly indicates the origin of fashions by imitation,
and also the peculiar resemblance we find in this respect between man
and his cousins, the apes. Sexual selection among the primates has a
good deal to do with this.

The great importance which Darwin ascribes in his _Descent of Man_
to the æsthetic selection of the respective sexes is equally true of
man and of all the higher vertebrates that have a feeling of beauty,
especially the amniotes (mammals, birds, and reptiles). The beautiful
coloring and marking and ornamentation which distinguish the males from
the females are due entirely to the careful individual selection of the
former by the latter. Thus the various kinds of ornamental hair (beard,
hair of head, etc.), the tint of the face, the peculiar form of the
lips, nose, ears, etc., are to be explained, as we find them in man and
the male ape; also the brilliant plumage of the humming-bird, the bird
of paradise, pheasant, etc. I have dealt fully with these interesting
facts in the eleventh chapter of the _History of Creation_, and must
refer the reader thereto. I will only point out here how valuable the
whole of this chapter of Darwinism is for the understanding of the
foundation of species on the one hand and men's fashions and customs on
the other. It is most closely connected with ethical problems.

The growth of fashion in civilized life is very important, not only for
the development of the sense of beauty and for the sexual selection
of the sexes, but also in connection with the origin of the feeling of
shame and the finer psychological traits that relate to it. The lower
savages have no more sense of shame than animals or children. They are
quite naked, and accomplish the sexual act without the slightest trace
of shame. The beginning of clothing which we find among the middle
savages is not due to a sense of shame, but partly to low temperature
(in the polar regions), partly to vanity and love of decoration (such
as ornamenting the ears, lips, nose, and sex-organs by the insertion
of shells, pieces of wood, flowers, stones, etc.). Afterwards the
sense of shame sets in, and we have the covering of certain parts of
the body with leaves, girdles, shirts, etc. In most nations the sexual
parts are the first to be covered; though some attach importance to the
veiling of the face. In many Oriental tribes (especially Mohammedan)
it is still the first precept of female chastity to veil the face (the
most characteristic part of the individual), while the rest of the body
may remain naked. Generally speaking, the æsthetic and psychological
relations of the sexes play the chief part in the higher development of
morals. Morality is often taken to be synonymous with the law of sexual
intercourse.

As the features of civilized life advance, the influence of reason
increases, and so does the power of hereditary tradition and the moral
ideas associated with it. The result is a severe conflict between the
two. Reason seeks to judge everything by its own standard, to learn
the causes of phenomena and direct practical life accordingly. On
the other hand tradition, or "good morals," looks at everything from
the point of view of our forefathers and other venerable laws and
religious precepts. It is indifferent to the independent discoveries
of reason and the real causes of things. It demands that the practical
life of every individual be framed in accordance with the hereditary
morality of the race or state. Thus we get the inevitable conflict
between reason and tradition, or science and religion, which continues
in our own day. Sometimes in the course of it a "new fashion" is
substituted for some sacred tradition, a transitory custom that
succeeds in imposing itself by its novelty or curiosity; and when this
has contrived to win general acceptance, or has gained the support of
Church or state to some extent, it is regarded in much the same light
as the older morality.

The lowest races of the present time (for instance, the pithecoid
pygmies, the Veddahs of Ceylon, the Akkas of Central Africa) are very
little higher than their primate ancestors in mental development. This
is also true of their habits of life and morals. As their ideas are for
the most part concrete and sensual, their power of forming abstract
concepts is very little developed; they have hardly any religious ideas
to speak of. But with the middle savages we begin to find the craving
to know the causes of things and the idea of spirits that are concealed
behind the phenomena of sense. Dread of these leads to worship,
fetichism, and animism, the beginning of religion. Even at this early
stage of worship we find certain customs associated with the cult to
which a symbolical or mysterious meaning is given. These ceremonies
lead on in the higher races to the great religious festivities,
which the Greeks called "mysteries." Sensual images of various kinds
are mixed up in them with supersensual ideas and superstitions. The
festivals, processions, dances, hymns, and sacrifices of all sorts that
form part of the cult are more or less concerned with the mysterious,
and are therefore considered "holy." They are often made the pretext of
sensual gratifications, which end in gross immorality and orgies.

From the older pagan and Jewish religious usages were afterwards
developed in the Christian Church those parts of the cult which are
known as sacraments. These miraculous sacraments, by the mysterious
action of which man is supposed to be born again or regenerated, very
quickly became powerful instruments in the hand of the Church and
thorny problems for theologians, especially after Gregory the Great
introduced the dogmas of Purgatory and the relieving power of the Mass.
According to St. Thomas of Aquin, the sacraments are channels that
convey the grace of God to sinful man. The papal authorities fixed
their number at seven (baptism, eucharist, penance, confirmation,
matrimony, orders, and extreme unction) in the twelfth century. The
superstitious content of these sacraments was generally lost sight
of in the glamour of their ceremonious side, but their authority was
unshaken. Since the Reformation the Protestants have retained only the
two chief sacraments which were founded by Christ himself--Baptism and
the Lord's Supper.

 Christian baptism is a continuation of the older ceremonies of
 washing and purification that were in use thousands of years before
 Christ among nations of the East and among the Greeks. They combined
 the hygienic value of the bath with the idea of a regeneration of the
 soul and spiritual purification. Augustine, who founded the dogma of
 original sin, held that the baptism of children was necessary for the
 salvation of their souls, and it then became general. It has since
 given rise to a number of superstitious ideas and unfortunate family
 troubles, but it is still regarded as a sacred ceremony. Millions of
 Christians still believe that the child's soul is saved (though it
 has no consciousness whatever when baptized) and delivered from the
 power of the devil and the curse of sin by baptism.

 The second sacrament that Luther retained is the Lord's Supper, or
 the sacrament of the body and blood of Christ. It was instituted by
 Christ on the night before his death, and is a continuation of the
 paschal supper of the Jews, in which the head of the house shared
 bread and wine with his family with certain ritual ceremonies. In
 this paschal supper the people of Israel celebrated their release
 from the bondage of Egypt and their distinction as the "chosen
 people." By connecting his "last supper" with the traditional
 rite of the Jews, Christ sought on the one hand to found the new
 dispensation on the old, and on the other hand to institute a
 love-feast (communion or agape) among his followers. Like baptism,
 the Lord's Supper led afterwards to the bitterest controversy among
 theologians.

 The differences of opinion as to the Eucharist in the Middle Ages
 culminated at last in the opposition of the two reformers, Luther and
 Zwingli. The latter, the founder of the Free Reformed Church, saw
 in the Supper only a symbolical act and a commemoration of Christ.
 Luther, however, adhered to the mysterious miracle that had been
 defined in 1215 by the dogma of transubstantiation. Bread and wine
 are believed on this view to be converted physically into the body
 and blood of Christ! I was taught this in 1848 by the minister who
 prepared me for confirmation, and to whom I was greatly attached. We
 were actually to perceive this change when we assisted at the Supper
 for the first time, if we did so with real faith. As I was quite
 conscious of having this quality, I had great expectations of the
 miracle. But I was very painfully disillusioned when I found only the
 familiar taste of bread and wine, not the flesh and blood that faith
 had desired. I had to regard myself (then a boy of fourteen years) as
 an utterly abandoned sinner, and it was with the greatest difficulty
 that my parents succeeded in pacifying me over my want of faith.

 I have spoken somewhat fully in the seventeenth chapter of the
 _Riddle_ of the view of the papacy and ultramontanism which modern
 historical and anthropological science leads us to form. No one
 who has any idea of history and of the metamorphoses of religion
 can question that Romanism is a miserable caricature of primitive
 Christianity; it retains the name, but has completely reversed the
 principles. In the course of its domination, from the fourth to the
 sixteenth century, the papacy has raised up the marvellous structure
 of the Catholic hierarchy, but has departed farther and farther
 from the stand-point of pure Christianity. The aim of Romanism is
 to-day, as it was a thousand years ago, to dominate and exploit a
 blindly believing humanity. It finds admirable instruments for this
 in its mystic sacraments, to which it has ascribed an "indelible
 character." From the cradle to the grave, from baptism to the last
 anointing, in confirmation and penance, the believer must be reminded
 that he must live as an obedient and self-sacrificing child; and the
 sacrament of ordination must teach him that the priest, with his
 higher inspiration, is the only intermediary between man and God. The
 symbolical rites that are associated with these sacraments serve
 to surround them with the magic of the mysterious and exclude the
 penetration of reason. This is particularly true of the sacrament
 that has had the greatest practical influence--matrimony.

In view of the extreme importance of the life of the family as a
foundation of social and civic life, it is advisable to consider
marriage from the biological point of view, as an orderly method of
reproduction. Here, as in all other sociological and psychological
questions, we must be careful not to accept the present features of
civilized life as a general standard of judgment. We have to take
a comparative view of its various stages, as we find them among
barbarians and savages. When we do this impartially, we see at once
that reproduction, as a purely physiological process having for its
end the maintenance of the species, takes place in just the same way
among uncultivated races as among the anthropoid apes. We may even say
that many of the higher animals, especially monogamous mammals and
birds, have reached a higher stage than the lower savages; the tender
relations of the two sexes towards each other, their common care of
their young, and their family life, have led to the development of
higher sexual and domestic instincts, to which we may fitly ascribe a
moral character. Wilhelm Bölsche has shown, in his _Life of Love in
Nature_, how a long series of remarkable customs has been developed
in the animal world by adaptation to various forms of reproduction.
Westermarck has pointed out, in his _History of Marriage_, how the
crude animal forms of marriage current among savages have been
gradually elevated as we rise to higher races. As the sensual pleasure
of generation is combined with the finer psychological feeling of
sympathy and psychic attachment, the latter gains constantly on the
former, and this refined love becomes one of the richest sources of the
higher spiritual functions, especially in art and poetry. Marriage
itself, of course, remains a physiological act, a wonder of life, with
the organic sex impulse as its chief foundation. As the conclusion
of marriage represents one of the most important moments in human
life, we find it accompanied by symbolic ceremonies and festive rites
even among lower tribes. The immense variety of marriage festivals
shows how this important act has appealed to the imagination. Priests
quickly recognized this, and decked out marriage with all kinds of
ceremonies and turned it to the advantage of their Church. While the
Catholic Church raised it to the status of a sacrament and ascribed to
it an "indelible" character, it declared that it was indissoluble when
performed according to ecclesiastical rite. This unwholesome influence
of Romanism, this dependence of matrimony on religious mysteries and
ceremonies, and difficulty of obtaining divorce, etc., still continue
in our day. It is only a short time since the German Reichstag, under
the influence of the Centre [Catholic] party, added laws to its civic
code which increase instead of lessening the difficulty of obtaining
divorce. Reason demands the liberation of marriage from ecclesiastical
pressure. It demands that matrimony be grounded on mutual love,
esteem, and devotion, and that it at the same time be counted a social
contract, and be protected, as civil marriage, by proper legislation.
But when the contracting parties find (as so often happens) that they
have mistaken each other's character, and that they do not suit each
other, they should be free to dissolve the bond. The pressure which
comes of marriage being regarded as a sacrament, and which prevents the
dissolution of unhappy marriages, is merely a source of vice and crime.

We find in many other features of our social life, besides marriage,
a contradiction between the demands of reason and the traditional
usages which modern civilization has taken over as a heritage from
earlier and lower nations, and partly from barbarians and savages. In
the public life of states this contradiction is much more striking
than in the private life of the family or the individual. Whereas the
milder teaching of the Christian religion--sympathy, love of one's
fellows, patience, and devotion--has had a good influence in many
ways, there can be no question of this in the international relations
of the nations; here we find pure egoism. Every nation seeks to take
advantage of others by cunning or force, and, wherever possible, to
subjugate them: if they will not consent, the brute force of war is
employed. Social misery of all kinds spreads wider and wider, almost in
proportion as civilization develops. Alexander Sutherland is right when
he characterizes "the leading nations of Europe and their offshoots"
(in the United States) as _lower_ civilized races. In some respects we
are still barbarians.

How far the bulk of modern nations still are from the ideal and
the reign of pure reason can be seen by a glance at the social,
juridical, and ecclesiastical condition of "these leading nations
of Europe," either Teutonic or Latin. We need only consider with an
unprejudiced mind the accounts in our journals of parliamentary and
legal proceedings, government measures and social relations, in order
to realize that the force of tradition and fashion is immense, and
resists the claims of reason on every side. This is most clearly seen
externally in the power of fashion, especially as regards clothing.
There is a good ground for the complaint about "the tyranny of
fashion." However unpractical, ridiculous, ugly, and costly a new
garment may be, it becomes popular if it is patronized by authority,
or some clever manufacturer succeeds in imposing it by specious
advertisements. We need only recall the crinoline of fifty years ago,
the bustle of twenty years ago, and the exposure of the breast and
back by low dresses (with the object of sexual excitement) which was
the fashion of forty years ago.[11] For centuries we have had the
pernicious fashion of the corset, an article that is as offensive from
the æsthetic as from the hygienic point of view. Thousands of women are
sacrificed every year to this pitiful fashion, through disease of the
liver or lungs; nevertheless, the craze for the hour-glass shape of the
female form continues, and the reform of clothing makes little headway.
It is just the same with numbers of fashions in the home and in
society, of devices in commerce and laws in the state. Everywhere the
demands of reason advance little in their struggle with the venerable
usages of tradition.

A false sense of honor dominates our social life, just as a false
sense of modesty controls our clothing. The true honor of man or woman
consists in their inner moral dignity, in the determination to do only
what they conceive to be good and right, not in the outer esteem of
their fellows or in the worthless praise of a conventional society.
Unfortunately, we have to admit that in this respect we are still
largely ruled by the foolish views of a lower civilization, if not of
crude barbarians.

In many other features of our life besides this false modesty and
false honor we perceive the force of social usage. Many of what are
thought to be honorable customs are relics of barbarism; much of our
morality is, in the light of pure reason, downright immorality. As
even the latter is due to adaptation, and as the same custom may be
at one time thought useful and fitting, at another time injurious
and bad, we see again that it is impossible to restrict the idea of
adaptation to useful variations. We may say the same of the changing
rules of education, commerce, legislation, and so on. The ideal in all
departments of life is pure reason; but it has to struggle long against
the current prejudices and customs, which find their chief support in
the superstitions of the Church and the conservative tendencies of the
state. In this state of Byzantine immorality, decorating itself so
often with the mantle of piety, practical materialism flourishes, while
monism, or theoretical materialism, is thrust aside.

If we sum up all that monistic science has taught us as to the origin
and development of morality, we may put it in the following series
of propositions: 1. By adaptation to different conditions of life
the simple plasm of the earliest organisms, the archigonous monera,
undergoes certain modifications. 2. As the living plasm reacts on
these influences, and the reaction is often repeated, a habit is
formed (as in the catalysis of certain inorganic chemical processes).
3. This habit is hereditary, the repeated impressions being fixed
in the nucleus (or caryoplasm) in the case of the unicellulars. 4.
When hereditary transmission lasts through many generations, and is
strengthened by cumulative adaptation, it becomes an instinct. 5. Even
in the protist cœnobia (the cell-communities of the protophyta and
protozoa) social instincts are formed by association of cells. 6.
The antithesis of the individual and social instinct, or of egoism
and altruism, increases in the animal kingdom in proportion to the
development of psychic activity and social life. 7. In the higher
social animals definite customs arise in this way, and these become
rights and duties when obedience to them is demanded by the society
(herd, flock, people) and the breach of them punished. 8. Savage races
at the lowest stage, without religion, are not differently related to
their customs than the higher social animals. 9. The higher savages
develop religious ideas, combine their superstitious practices
(fetichism and animism) with ethical principles, and transform their
empirical moral laws into religious commands. 10. Among barbaric, and
more particularly among civilized, races definite moral laws are formed
by the association of these hereditary religious, moral, and legal
ideas. 11. In the civilized races the Church formulates the religious
commands, and jurisprudence the legal commands, in more definitely
binding forms; the advancing mind remains, however, subject in many
respects to Church and state. 12. In the higher civilized nations pure
reason gains more and more influence on practical life, and thrusts
back the authority of tradition; on the basis of biological knowledge a
rational or monistic ethic is developed.




XIX

DUALISM

 Dualistic systems of Kant I. and Kant II.--His
 antinomies--Cosmological dualism--The two worlds--The world
 of bodies and the world of spirits--Truth and fiction--Goethe
 and Schiller--Realism and idealism--Anti-Kant--Law of
 substance--Attributes of substance--Sensation and energy--Passive
 and active energy--Trinity of substance: matter, force, and
 sensation--Constancy of sensation--Psyche and physics--Reconciliation
 of principles.


The history of philosophy shows how the mind of man has pressed along
many paths during the last two thousand years in pursuit of truth.
But, however varied are the systems in which its efforts have found
embodiment, we may, from a general point of view, arrange them all
in two conflicting series--monism, or the philosophy of unity; and
dualism, or the philosophy of the duality of existence. Lucretius
and Spinoza are distinguished and typical representatives of monism;
Plato and Descartes the great leaders of dualism. But besides the
consistent thinkers of each school there are a number of philosophers
who vacillate between the two, or who have held both views at different
periods of life. Such contradictions represent a personal dualism on
the part of the individual thinker. Immanuel Kant is one of the most
famous instances of this class; and as his critical philosophy has
had a profound influence, and I was compelled to contrast my chief
conclusions with those of Kant, I must once more deal briefly with his
ideas. This is the more necessary as one of the ablest of the many
attacks on the _Riddle_, the _Kant against Haeckel_ of Erich Adick, of
Kiel, belongs to this school.

In the _Creed of Pure Reason_, which I published as an appendix to
the popular edition of the _Riddle_ in 1903, I pointed out, in view
of this and similar Kantist criticisms, the clear inconsistency of
the great evolutionary principles of Kant, the natural philosopher,
with the mystic teaching which he afterwards made the foundation of
his theory of knowledge, and that is still greatly esteemed. Kant I.
explained the constitution and the mechanical origin of the universe
on Newtonian principles, and declared that mechanicism alone afforded
a real explanation of phenomena; Kant II. subordinated the mechanical
principle to the teleological, explaining everything as a natural
design. Kant I. convincingly proved that the three central dogmas
of metaphysics--God, freedom, and immortality--are inacceptable to
pure reason. Kant II. claimed that they are necessary postulates of
practical reason. This profound opposition of principles runs through
Kant's whole philosophic work from beginning to end, and has never been
reconciled. I had already shown in the _History of Creation_ that this
inconsistency has a good deal to do with Kant's position in regard to
evolution. However, this radical contradiction of Kant's views has
been recognized by all impartial critics. It has lately been urged
with great force by Paul Rée in his _Philosophy_ (1903). We need not,
therefore, linger in proving the fact, but may go on to consider the
causes of it.

A subtle and comprehensive thinker like Kant was naturally perfectly
conscious of the existence of this inconsistency of his dualistic
principles. He endeavored to meet it by his theory of antinomies,
declaring that pure reason is bound to land in contradictions when
it attempts to conceive the whole scheme of things as a connected
totality. In every attempt to form a unified and complete view
of things we encounter these unsolvable antinomies, or mutually
contradictory theses, for both of which sound proof is available.
Thus, for instance, physics and chemistry say that matter must consist
of atoms as its simplest particles; but logic declares that matter
is divisible _in infinitum_. On the one theory time and space are
infinite; on the other theory, finite. Kant attempted to reconcile
these contradictions by his transcendental idealism, by the assumption
that objects and their connection exist only in our imagination, and
not in themselves. In this way he came to frame the false theory of
knowledge which is honored with the title of "criticism," while as a
matter of fact it is only a new form of dogmatism. The antinomies are
not explained by it, but thrust aside; nor was there more truth in the
assertion that equal proof is available for theses and antitheses.

The famous work of Kant's earlier years, _The General Natural History
and Theory of the Heavens_ (1755), was purely monistic in its chief
features. It embodied a fine attempt "to explain the constitution
and mechanical origin of the universe on Newtonian principles." It
was mathematically established forty years afterwards by Laplace in
his _Exposition du système du monde_ (1796). This fearless monistic
thinker was a consistent atheist, and told Napoleon I. that there was
no room for "God" in his _Mécanique celeste_ (1799). Kant, however,
afterwards found that, though there was no rational evidence of the
existence of God, we must admit it on moral grounds. He said the same
of the immortality of the soul and the freedom of the will. He then
constructed a special "intelligible world" to receive these three
objects of faith; he declared that the moral sense compelled us to
believe in a supersensual world, although pure theoretical reason
is quite unable to form any distinct idea of it. The categorical
imperative was supposed to determine our moral sense and the
distinction between good and evil. In the further progress of his
ethical metaphysics Kant expressly urged that practical reason should
take precedence of theoretical--in other words, that faith is superior
to knowledge. In this way he enabled theology and irrational faith
to find a place in his system and claim supremacy over all rational
knowledge of nature.

The older Greek philosophy had been purely monistic, Anaximander and
his disciple Anaximenes (in the sixth century B.C.) conceiving the
world in the sense of our modern hylozoism, but Plato introduced (two
hundred years afterwards) the dualistic view of things. The world of
bodies is real, accessible to our sensible experience, changeable and
transitory; opposed to it is the world of spirits, only to be reached
by thought, supersensual, ideal, immutable, and eternal. Material
things, the objects of physics, are only transient symbols of the
eternal ideas, which are the subject of metaphysics. Man, the most
perfect of all things, belongs to both worlds; his material frame is
mortal, the prison of the immortal and invisible soul. The eternal
ideas are only embodied for a time in the world of bodies here below;
they dwell eternally in the world of spirits beyond, where the supreme
idea (God, or the idea of the good) controls all in perfect unity.
The human soul, endowed with free-will, is bound to develop the three
cardinal virtues (wisdom, fortitude, and prudence) by the cultivation
of its three chief moral faculties (thought, courage, and zeal). These
fundamental principles of Plato's teaching, systematically presented
by his pupil Aristotle, met with a very general acceptance, as they
could easily be combined with the teaching of Christianity which arose
four hundred years afterwards. The great majority of later philosophic
and religious systems followed the same dualistic paths. Even Kant's
metaphysics is only a new form of it; only its dogmatic character
is hidden by the ascription to it of the convenient title of the
"critical" system.

Modern science has opened out to us immense departments of the real
world that are accessible to observation and rational inquiry; but it
has not taught us a single fact that points to the existence of an
immaterial world. On the contrary, it has shown more and more clearly
that the supposed world beyond is a pure fiction, and only merits to be
treated as a subject for poetry. Physics and chemistry in particular
have proved that all phenomena that come under our observation depend
on physical and chemical laws, and that all can be traced to the
comprehensive and unified law of substance. Anthropogeny has taught us
the evolution of man from animal ancestors. Comparative anatomy and
physiology have shown that his mind is a function of the brain, and his
will not free; and that his soul, absolutely bound up with its material
organ, passes away at death like the souls of other mammals. Finally,
modern cosmology and cosmogony have found no trace whatever of the
existence and activity of a personal and extramundane God. All that
comes within the range of our knowledge is a part of the material world.

In his observations on the supersensual world Kant lays stress on the
fact that it lies beyond the range of experience, and is known only by
faith. Conscience, he thinks, assures us of its existence, but does
not give us any idea of its nature; and so the three central mysteries
of metaphysics are mere words without meaning. But, as nothing can
be done with mere words, Kant's followers have attempted to put a
positive substance into them, generally in relation to traditional
ideas and religious dogmas. Not only orthodox Kantians, but even
critical philosophers like Schleiden, have dogmatically asserted that
Kant and his disciples have established the transcendental ideas of
God, freedom, and immortality, just as Kepler, Newton, and Laplace
established the laws of celestial motion. Schleiden imagined that this
dogmatic affirmation would refute "the materialism of modern German
science." Lange has shown, on the contrary, that such dogmatism is
utterly foreign to the spirit of the _Critique of Pure Reason_, and
that Kant held the three ideas to be quite incapable of either positive
or negative proof, and so thrust them into the domain of practical
philosophy. Lange says: "Kant would not see, as Plato would not see
before him, that the intelligible world is a world of poetry, and has
no value except in this respect." But if these ideas are mere figments
of the poetic imagination, if we can form neither positive nor negative
idea of them, we may well ask: What has this imaginary spirit-world to
do with the pursuit of truth?

As I have raised the question of the limits of truth and fiction, I
may take the opportunity of pointing out the general importance of
this distinction. Undoubtedly man's knowledge is limited, from the
very nature of our faculties or the organization of our brain and
sense-organs. Hence, Kant is right when he says that we perceive only
the phenomena of things, and not their inner essence, which he calls
the "thing in itself." But he is wrong and altogether misleading
when he goes on to doubt the reality of the external world, and says
it exists only in our presentations--in other words, that life is a
dream. It does not follow, from the fact that our senses and phronema
can reach only a part of the properties of things, that we call into
question their existence in time and space. But our rational craving
for a knowledge of causes impels us to fill up the gaps in our
empirical knowledge by our imagination, and thus form an approximate
idea of the whole. This work of the imagination may be called
"fiction" in a broad sense--hypotheses when they are in science, faith
when they belong to religion. However, these imaginative constructions
must always take a concrete form. As a fact, the imagination that
constructs the ideal world is never content merely to assume its
existence, but always proceeds to form an image of it. But these forms
of faith have no theoretical value for philosophy if they contradict
scientific truth, or profess to be more than provisional hypotheses;
otherwise they may be of practical service, but are theoretically
useless. Hence we fully recognize the great ethical and pedagogical
value of poetry and myths, but are by no means disposed to give them
precedence of empirical knowledge in our quest of the truth. I agree
entirely with the excellent criticism of Kant which Albert Lange gives
in his _History of Materialism_ (vol. ii.); but I am unable to follow
him when he transfers his idealism from practical to theoretical
questions, and urges the erroneous theory of knowledge derived from it
in opposition to monism and realism. It is true that, as Lange says:

 Kant did not lack the sense for the conception of this intelligible
 world (as an imaginative world); but his whole education and the
 period in which his mental life developed prevented him from
 indulging it. As he was denied the liberty of giving a noble form,
 free from all mediæval distortion, to the vast structure of his
 ideas, his positive philosophy was never fully developed. His system,
 with its Janus face, stands at the limit of two ages. He himself,
 in spite of all the defects of his deductions, is a teacher of the
 ideal. Schiller especially has grasped with prophetic insight the
 very essence of his teaching, and purified it of its scholastic
 dross. Kant held that we must only think, not see, the intelligible
 world; though what he thinks must have objective reality. Schiller
 has rightly brought the intelligible world visibly before us by
 treating it as a poet, and thus following in the footsteps of Plato,
 who, in contradiction to his own dialectic, reached his highest
 thought when he allowed the supersensual to become a thing of sense
 in the myth. Schiller, the poet of freedom, dared to carry freedom
 openly into the land of dreams and of shadows; then there arose under
 his hand the dreams and shadows of the ideal.

In view of the great influence that Schiller's idealism has had in
the spread of Kant's practical moral philosophy, we may for a moment
consider it in contrast with the realistic views of Goethe.

The profound opposition of the views of the two greatest poets of
the classical period of German literature is rooted deep in their
natures. This has been proved so often and so thoroughly, and has so
frequently been represented as the complementary quality of the two
poets, that I need merely recall it here. As for Goethe, I have, in my
_General Morphology_, shown his historical importance in connection
with the theory of evolution and the system of monism. With all his
versatile occupations, this great genius found time to devote to the
morphological study of organisms, and to establish his comprehensive
biological theories on this empirical basis. His discovery of the
metamorphosis of plants and his vertebral theory of the skull justify
us in classifying him as one of the chief forerunners of Darwin.
When I dealt with this in the fourth chapter of the _History of
Creation_, I pointed out how great an influence these morphological
studies, together with his idea of evolution, had on the realism of
his philosophy. They led him direct to monism and to an admiration of
Spinoza's monistic pantheism. Schiller had neither great interest nor
clear insight for these studies. His idealistic philosophy disposed
him rather to Kant's dualistic metaphysics and to an acceptance of
the three central mysteries--God, soul, and freedom. Both Schiller
and Goethe had a thorough knowledge of anthropology and psychology.
But the anatomic and physiological studies that Schiller made as a
military surgeon had very little influence on his transcendental
idealism, in which the ethical-æsthetic element preponderated. On the
other hand, Goethe's empirical realism was profoundly influenced by his
medical studies at Strasburg, and especially by his later comparative
anatomical and botanical investigations at Jena and Weimar.

The philosophic antithesis which we thus find in the biological
foundations of the views of Goethe and Schiller represents to an extent
the Janus face that the philosophic genius of the German people bears
to our own day. Goethe, the realist, penetrated deep into the empirical
study of the material world, and sought, with Spinoza, to establish
the unity of the universe. Schiller, the idealist, lives rather
in the spirit-world, and seeks, with Kant, to utilize its ethical
ideals--God, freedom, and immortality--for the education of the human
race. Both tendencies of thought have led the genius of Germany--like
the genius of Greece, two thousand years ago--to a great number of vast
intellectual achievements. Goethe wrought the ideal in his practical
life, Kant discovered it, Schiller proclaimed it to be the fittest aim
of the future.

It is wrong to conclude from isolated quotations from Goethe that he
occasionally betrayed the dualism of Schiller in his opinions. Some
of the remarks in this connection that Eckermann has left us from his
conversations with Goethe must be taken very carefully. Generally
speaking, this source is not reliable; many of the observations that
the mediocre Eckermann puts into the mouth of the great Goethe are
quite inconsistent with his character, and are more or less perverted.
Hence, when recent high-placed orators declare at Berlin that Goethe
saved the high ideals of God, freedom, and immortality, like Schiller,
and thus borrow a certain support for their Christian belief, they only
show how little they have grasped the profound antithesis of the views
of the two poets. Goethe notoriously described himself as a "renegade
non-Christian." The creed of the "great heathen" Goethe, as we find
it in _Faust_ and _Prometheus_ and _God and the World_, and a hundred
other magnificent poems, is pure monism, of the pantheistic character
which we take to be alone correct--hylozoism; he is equally far from
the one-sided materialism of Holbach or Carl Vogt and the extreme
dynamism of Leibnitz and Ostwald. Schiller by no means shared this
realistic view of things; his idealistic sense fled beyond nature into
the spirit world. However, our theoretic hylozoism does not exclude
practical idealism, as Goethe's whole life showed. On the other hand,
princes and priests often let us see how easily theoretical idealism
goes with practical materialism, or hedonism.

In the month of February, 1904, the centenary of the death of Kant was
celebrated throughout the world of culture. In numbers of academic
speeches and writings he was greeted as the greatest thinker of
Germany. He died on the same date (February 12th) on which Darwin
was born five years later. It is unquestionable that Kant has had
an immense influence on the whole development of German philosophy.
But while recognizing his extraordinary genius, we must not be blind
to the glaring contradictions and defects of his dualist system.
From the monistic point of view, we can only regard his profound
influence during the whole of the nineteenth century as mischievous.
Most certainly he had a quite exceptional talent for philosophic
speculation and penetrating thought, and he added to his great mental
qualities a blameless character and an undeniable sense of truth in
life (though not in thought). It was a serious misfortune for Kant and
for the philosophic school he led that his education prevented him
from acquiring a thorough knowledge and correct conception of the real
world. Shut up throughout life within the narrow bounds of his native
town, Königsberg, he never travelled beyond the frontier of Prussia,
and so did not obtain that knowledge of the world that comes of
travelling. In the study of nature he confined himself to the physics
of the inorganic world, in the study of man to the immortal soul. At
the close of his university studies Kant had to earn his living as a
house-teacher for nine years (from twenty-two to thirty-one), just
at the most important period of his life, in which the independent
development of the personal and scientific character is decided when
the academic studies are over.

In such adverse circumstances of mental adaptation a deep mystic trait,
which had been inherited from pious parents and confirmed by the
strictly religious training of his early years, was fixed in Kant's
character. Hence it was that faith in the three central mysteries came
upon him more and more in later years: he gave them precedence over all
the attainments of theoretical reason, while granting that we can form
neither a negative nor positive idea of them. But how can the belief
in God, freedom, and immortality determine one's whole view of life as
a postulate of practical reason if we cannot form any definite idea of
them?

Every philosophy that deserves the name must have clear ideas as
the bases of its thought-structure; it must have definite views in
connection with its fundamental conceptions. Hence most of Kant's
followers have not been content to follow his direction merely
to _believe_ in the three central mysteries; they have sought to
associate definite mental pictures with the empty concepts of God,
freedom, and immortality. In this they have drawn upon the religious
imagination, and have passed from the real knowledge of nature into the
transcendental realm of poetry. Monism, based on this real knowledge of
nature, has to keep clear of such dualism.

The extraordinary glorification of Kant that took place on the occasion
of his centenary must have seemed strange to many scientists who
recognize in his idealism one of the greatest hinderances to the spread
of the modern monistic philosophy of nature. But it is not difficult to
explain this. We must remember, in the first place, the contradictory
views that are embodied in Kant's system; every one could find in
Kant's works something to correspond to his own convictions--the
monistic physicist could read of the mechanical sway of natural law
throughout the whole knowable world, and the dualistic metaphysician of
the free play of the divine aim in the spiritual world. The physician
and physiologist would note with satisfaction that in his criticism of
pure reason Kant had been unable to find any evidence for the existence
of God, the immortality of the soul, or the freedom of the will. The
jurist and theologian would find with equal gratification that in the
practical reason Kant claims these three central dogmas as necessary
postulates. I have shown to some extent, in the sixth chapter of the
_Riddle_, how these irreconcilable contradictions in Kant's system are
due to a psychological metamorphosis.

It is just these very contradictions, which run through Kant's
philosophy from beginning to end, that maintain its popularity.
Educated people who desire to form a view of life rarely read Kant's
difficult (and often obscure) works in the original, but are content
to learn from extracts, or from a history of philosophy, that the
Königsberg thinker succeeded in squaring the circle, or in reconciling
natural science with the three central dogmas of metaphysics. The
"higher powers," who are particularly concerned to save the latter,
favor the teaching of Kant's dogmas, because it closes the way to real
explanation and prevents independent thinking. This is especially
true of the ministers of public instruction in the two chief German
states--Prussia and Bavaria. In their open attempt to subordinate the
school to the Church, they desire, above all, the primacy of practical
reason--that is to say, the subjection of pure reason to faith and
revelation. In German universities to-day belief in Kant is a sort of
ticket of admission to the study of philosophy. The reader who would
realize the pernicious effect of this official faith in Kant on the
advance of scientific knowledge will do well to read the able criticism
in the brilliant posthumous work of Paul Rée.

In the face of the dualism which still prevails in the academic
teaching of philosophy (especially in Germany) we must base our
monistic system on the universality of the law of substance. This
harmoniously combines the laws of the conservation of matter and of
energy. As I have fully explained my own conception of this law in
the twelfth chapter of the _Riddle_, I will only say here that its
validity is quite independent of any particular theory of the relations
of matter and force.[12] The materialism of Holbach and Büchner lays a
one-sided stress on the importance of matter: the dynamism of Leibnitz
and Ostwald on that of force. If we avoid these extremes, and conceive
matter and force as inseparable attributes of substance, we have pure
monism, as we find it in the systems of Spinoza and Goethe. We might
then substitute for the word "substance" as Hermann Cröll does, the
term "force-matter." The further question as to the correctness of any
particular physical conception of matter is quite independent of this.

The two knowable attributes or inalienable properties of substance,
without which it is unthinkable, were described by Spinoza as extension
and thought; we speak of them as matter and force. The "extended" (or
space-occupying) is matter; and in Spinoza "thought" does not mean a
particular function of the human brain, but energy in the broadest
sense. While hylozoistic monism conceives the human soul in this
sense as a special form of energy, the current dualism or vitalism
affirms, on the authority of Kant, that psychic and physical forces
are essentially different; that the former belong to the immaterial
and the latter to the material world. The theory of psycho-physical
parallelism, as developed especially by Wundt (1892), gives a very
sharp and definite expression to this dualism; it says that "physical
processes correspond to every psychic phenomenon, but the two are
completely independent of each other and have no natural causal
connection."

This wide-spread dualism finds its chief support in the difficulty of
directly connecting the processes of sensation with those of movement;
and so the one is regarded as a psychic and the other as a physical
form of energy. The conversion of the outer stimulus (waves of light,
sound, etc.) into an inner sensation (sight or hearing) is regarded
by monistic physiology as a conversion of force, a transformation of
photic or acoustic energy into specific nerve-energy. The important
theory of the specific energy of the sensory nerves, as formulated by
Johannes Müller, forms a bridge between the two worlds. But the idea
which these sensations evoke, the central process in the thought-organ
or phronema that brings the impressions into consciousness, is
generally regarded as an incomprehensible mystery. However, I have
endeavored to prove, in the tenth chapter of the _Riddle_, that
consciousness itself is only a special form of nervous energy, and
Ostwald has lately developed the theory in his _Natural Philosophy_.

The processes of movement which we observe in every change of one form
of energy into another, or every passage of potential into actual
energy, are subordinate to the general laws of mechanics. The dualist
metaphysic has rightly said that the mechanical philosophy does not
discover the inner causes of these movements. It would seek these in
psychic forces. On our monistic principles they are not immaterial
forces, but based on the general sensation of substance, which we
call _psychoma_, and add to energy and matter as a third attribute of
substance.

The difficulty of combining our monism with Spinoza's doctrine of
substance is met by detaching the idea of energy from sensation and
restricting it to mechanics, so as to make movement a third fundamental
property of substance with matter (the "extended") and sensation (the
"thinking"). We may also divide energy into active (= will in the sense
of Schopenhauer) and passive (= sensation in the broadest sense). As a
matter of fact, the energy to which modern energism would reduce all
phenomena has not an independent place in Spinoza's system besides
sensation; the attribute of thought (the psyche, soul, force) comprises
the two. I am convinced that sensation is, like movement, found in
all matter, and this trinity of substance provides the safest basis
for modern monism. I may formulate it in three propositions: (1) No
matter without force and without sensation. (2) No force without matter
and without sensation. (3) No sensation without matter and without
force. These three fundamental attributes are found inseparably united
throughout the whole universe, in every atom and every molecule. In
view of the great importance of this view for our hylonistic system of
monism, it may be well to consider each of these three attributes in
connection with the law of substance.

_A._ MATTER.--As extended substance, matter occupies infinite space,
and each individual body forms a part of the universe as real
substance. The law of the conservation of matter teaches us that the
sum of matter is eternal and unchangeable. This applies equally to
the various kinds of matter which we call the chemical elements, or
ponderable matter, and to the ether that fills the spaces between
the atoms and molecules, or imponderable matter. The mischievous
depreciation of matter (and the consequent disdain of materialism) and
its antithesis to "spirit" is partly due to the use of such phrases as
"raw" and "dead" matter, and partly to the deep-rooted mysticism we
have inherited from barbaric ancestors, and find it hard to shake off.

_B._ ENERGY.--All parts of the substance that fills infinite space
are in constant and eternal motion. Every chemical process and every
physical phenomenon is accompanied by a change in the position of the
particles which compose the matter. The law of the conservation of
energy teaches us that the sum of force or energy that is ever at work
in the universe is unchangeable. In the formation or decomposition of a
chemical compound the particles of matter move about, and so in every
mechanical, thermic, electric, and other process. The changes that
take place depend on a constant change of force, both in organic and
inorganic bodies; one form of force is converted into another without
a particle of the whole being lost. This law of the conservation of
force has lately been called, as a rule, the conservation of energy (or
the principle of energy) since the ideas of force and energy have been
more clearly distinguished in physics; energy is now usually defined as
the product of force and direction. It must be noted, however, that
the word "energy" (as an equivalent to "work" in the physical sense)
is still used in many different senses, as is also the word "force."
Others define energy as "work or all that comes of work and may be
converted into work." One particular school of voluntarism (Wundt)
reduces the motive-force of energy to will. Crusius said in 1744: "Will
is the dominating force in the world." And Schopenhauer defines the
world (or substance) as "will and presentation."

_C._ SENSATION.--In describing sensation (in the broadest sense) as
a third attribute of substance, and separating "sensitive substance"
from energy as "moving substance," I rely on the observations I made in
the thirteenth chapter of the _Riddle_ on sensation in the organic and
inorganic world. I cannot imagine the simplest chemical and physical
process without attributing the movements of the material particles to
unconscious sensation. In this sense the chemist speaks every day of a
sensitive reaction, and the photographer of a sensitive plate. The idea
of chemical affinity consists in the fact that the various chemical
elements perceive the qualitative differences in other elements,
experience "pleasure" or "revulsion" at contact with them, and execute
their specific movements on this ground. The sensitiveness of the plasm
to all kinds of stimuli, which is called "soul" in the higher animals,
is only a superior degree of the general irritability of substance.
Empedocles and the panpsychists spoke in the same sense of sensation
and effort in all things. As Nägeli said: "If the molecules possess
something that is related, however distantly, to sensation, it must
be comfortable to be able to follow their attractions and repulsions;
uncomfortable when they are forced to do otherwise. Thus we get a
common spiritual bond in all material phenomena. The mind of man is
only the highest development of the spiritual processes that animate
the whole of nature." These views of the distinguished botanist fully
agree with my monistic principles.

When sensation in the widest sense (as _psychoma_) is joined to matter
and energy as a third attribute of substance, we must extend the
universal law of the permanence of substance to all three aspects of
it. From this we conclude that the quantity of sensation in the entire
universe is also eternal and unchangeable, and that every change of
sensation means only the conversion of one form of psychoma into other
forms. If we start from our own immediate sensations and thoughts, and
look out on the whole mental life of humanity, we see through all its
continuous development the constancy of the psychoma, which has its
roots in the sensations of each individual. This highest achievement
of the work of the plasm in the human brain was, however, first
developed in the sensations of the lower animals, and these are in turn
connected by a long series of evolutionary stages with the simpler
forms of sensation that we find in the inorganic elements, and that
reveal themselves in chemical affinity. Albrecht Rau expressly says
in his excellent _Sensation and Thought_ (1896) that "perception or
sensation is a universal process in nature. This involves, moreover,
the possibility of reducing thought itself to this universal process."
Recently Ernst Mach has said, in his _Analysis of Sensation and the
Relation of the Physical to the Psychical_, that "sensations are the
common elements of all possible physical and psychic occurrences, and
consist simply in the different mode of the combination of the elements
and their dependence on each other." It is true that Mach, in his
one-sided emphasis of the subjective element of sensation, goes on to
form a similar psychomonism to that of Verworn, Avenarius, and other
recent dynamists; but the fundamental character of his system is purely
monistic, like the energism of Ostwald.

In thus uniting sensation with force and matter as an attribute of
substance, we form a monistic trinity, and are in a position to do away
with the antitheses that are rigidly maintained by dualists between the
psychic and the physical, or the material and the immaterial world.
Of the three great monistic systems materialism lays too narrow a
stress on the attribute of matter, and would trace all the phenomena
of the universe to the mechanics of the atoms or to the movements of
their ultimate particles. Spiritualism, with equal narrowness, builds
on the attribute of energy; it would either explain all phenomena by
motor forces or forms of energy (energism), or reduce them to psychic
functions, to sensation or psychic action (panpsychism). Our system of
hylonism (or hylozoism) avoids the faults of both extremes, and affirms
the identity of the psyche and the physis in the sense of Spinoza and
Goethe. It meets the difficulties of the older theory of identity by
dividing the attribute of thought (or energy) into two co-ordinate
attributes, sensation (psychoma) and movement (mechanics).




XX

MONISM

 Defence of monism--Pure and applied science (theoretic and
 practical reason)--Pure (theoretical) sciences: physics,
 chemistry, mathematics, astronomy, geology; biology, anthropology,
 psychology, philology, history--Applied (practical) sciences:
 medicine, psychiatry, hygiene, technology, pedagogics, ethics,
 sociology, politics, jurisprudence, theology--Antinomy of the
 sciences--Rational and dogmatic disciplines--Correlation of the
 sciences--Faculties--Reform of education--The ideal world--Harmony of
 monism.


Now that we have reached the end of our long journey, we may take a
general survey of the path we have pursued, and say how far we owe our
progress to the monistic philosophy. In doing so, we shall at once
justify our own point of view and indicate the relation of biology to
the other sciences. I feel the more bound to do this as the present
volume is not only a necessary supplement to the _Riddle_, but at the
same time my last philosophic work. At the end of my seventieth year I
would supply some of the defects of the _Riddle_, answer some of the
most stringent criticisms directed against it, and as far as possible
complete the philosophy of life at which I worked for half a century.

In inviting my readers to accompany me once more through the broad
domain of the monistic philosophy I must, as their modest guide, show
scientific justification at the narrow entrance--produce, so to say,
the ticket of admission to this investigation. The academic philosophy
which still controls the German universities watches every door with
jealous eyes, and has an especial concern to keep out modern biology.
Official German philosophy is still for the most part taken up with
a mediæval metaphysic and the dualism of Kant, the openly dogmatic
character of which it greets as "criticism." In the course of the forty
years during which I have taught as ordinary professor of zoology at
Jena I have had occasion to assist at several hundred examinations of
doctors, teachers, etc., in which distinguished representatives of
philosophy were examiners. I saw that nearly always the chief stress
was laid on a kind of conceptual gymnastics and self-observation, and
on the correct knowledge of the innumerable errors which the (mainly
dualistic) leaders of ancient and modern philosophy have left us in
their vast literature. The central feature of the whole scheme is
Kant's theory of knowledge, the defects and one-sidedness of which I
have treated in the first and nineteenth chapters. In psychology a most
extensive knowledge of psychic powers on the basis of the introspective
method is demanded; the physiological analysis of the "soul" and the
anatomic study of the phronema are carefully avoided, as are also the
comparative and genetic study of the mind. Many of our metaphysicians
go even farther and regard philosophy as a separate science--a sublime
"mental science," quite independent of the common empirical sciences.
One is tempted to quote the saying of Schopenhauer: "It is a sure
sign of a philosopher that he is not a professor of philosophy." In
my opinion, every educated and thoughtful man who strives to form a
definite view of life is a philosopher. As queen of the sciences,
philosophy has the great task of combining the general results of the
other sciences, and of bringing their rays of light to a focus as in
a concave mirror. The various tendencies of thought that arise in
such numbers have all a right to scientific respect and discussion,
the monistic minority no less than the dualistic majority. We have to
inquire, then, how far monism has succeeded in gaining firm foothold
in the various fields of science, and we may begin with a distinction
between pure (theoretical) and applied (practical) science.

Pure philosophy aims at a knowledge of the truth by means of pure
reason, as I explained in the first chapter. However, this theoretical
philosophy finds itself in most of the sciences in direct and
frequently important relations to practical life, and so in the form
of applied philosophy becomes a weighty factor in civilization. In
this the real claims of practical life are often in contradiction to
the ideal tenets of the scientifically grounded theory. In such cases,
in my opinion, the pure pursuit of the truth must take precedence of
applied philosophy. I thus dissent entirely from the view of Kant,
who expressly gives precedence to practical reason, and subordinates
theoretical reason to it. Kant's error was fated to have a terrible
influence, because the dominant authorities in Church and state eagerly
embraced it to insure everywhere the supremacy of the dogmas of
practical reason over the attainments of pure critical reason.

From the point of view of natural monism we may take physics in the
wider sense as the fundamental science. The term _physis_ (the Greek
equivalent of the Latin "nature"), in its original meaning, comprises
the whole knowable world--Kant's _mundus sensibilis_. His supersensual
or "intelligible" world is, on his own definition, the object of
faith, not knowledge. It is very remarkable to find a thinker like
Kant contradicting himself already in his fundamental distinction
of the two worlds. How can the supersensual world, with its three
central mysteries (God, freedom, and immortality), be described as
intelligible (_i.e._, knowable) when it is proved by pure reason that
the human mind is incapable of knowing it, or of forming any positive
or negative idea of it? _Lucus a non lucendo!_ We may, therefore, leave
this supernatural metaphysical world to faith and fiction, and confine
our studies to the real physical world, nature. The idea of physics
as a comprehensive natural philosophy, as it was conceived in classic
Greece, has been more and more restricted in the course of time. To-day
it is generally taken to mean the science of the phenomena of inorganic
nature, their empirical determination by observation and experiment
(experimental physics), and their reduction to fixed natural laws and
mathematical formulæ (theoretical or mathematical physics). Of late a
distinction has been drawn between the physics of mass and the physics
of ether; the one deals with mechanics, the movement and equilibrium
of ponderable matter, of solid, fluid, and gaseous bodies (statics and
dynamics, gravitation, acoustics, meteorology); the other is occupied
with the phenomena of ether (or imponderable matter) and its relations
to mass (electricity, galvanism, magnetism, optics, and calorics).
In all these branches of inorganic physics the monistic view is now
generally received, and all attempt at dualistic explanation abandoned.

The vast department of chemistry, which has now become so important
both for theoretical and practical purposes, is really only a part of
physics. But while modern physics restricts itself to the study of
inorganic forms of energy and their conversions, chemistry, as the
science of matter, takes up the study of the qualitative differences
between the various kinds of ponderable matter. It divides ponderable
bodies into some seventy-eight elements, the relations of which to each
other have been determined in the periodic system of the elements, and
their probable common origin from some primitive matter (prothyl)
been shown. The constant features of chemical combinations which have
been established by the analysis and synthesis of the elements, and
especially the law of simple and multiple proportions discovered in
1808, led to the empirical determination of the atomic weight of the
elements and to the chemical theory of the atom. The acceptance of
these atoms (as space-filling separate particles of matter--however
we may regard them in other respects) is an indispensable hypothesis
in chemistry, like the hypothesis of the molecule in physics. Modern
dynamism (or energism) is wrong when it thinks it can dispense with
these hypotheses and replace the atoms by the notion of immaterial
non-spatial points of force. However, in both the dynamic and the
material school monism is retained in every department of chemistry.

Modern science considers the ultimate aim of all research to be
the exact determination of phenomena in measure and number, or the
reduction of all general knowledge to mathematically formulated laws.
As the great Laplace established his system mathematically, it has
lately been claimed that a comprehensive (ideal) Laplace-mind could
embrace the whole past, present, and future of the universe in a single
gigantic mathematical formula. Kant has expressed this exaggerated
estimate of mathematics in the phrase: "Every science is only true
science in proportion as it is amenable to mathematical treatment";
and to this he has added the second error that the mathematical axioms
(being necessary and universal truths) belong to the _a priori_
constitution of the mind, and are independent of experience (_a
posteriori_). However, John Stuart Mill and others have shown that
the fundamental ideas of mathematics are acquired originally, like
those of any other science, by abstraction from experience; and the
modern phylogeny of the mind has confirmed this empirical view. We
must remember, moreover, that mathematics deals only with quantitative
relations in time and space, and not with the qualitative features of
bodies. In fact, Kant himself showed that mathematics only answers for
the absolute _formal_ correctness of conclusions it draws from given
premises, and has no influence on the premises themselves. Hence,
when we examine the abstract thinking-power of the phronema in its
mathematical operations physiologically and phylogenetically, we find
that even this "exact fundamental science" is only accessible to pure
monism and excludes all dualism. The great regard which mathematics
enjoys as an exact science in all branches of knowledge is chiefly
due to its _formal accuracy_, and to the possibility of expressing
infallibly spatial and time quantities in number and mass.

Astronomy is one of the older sciences that took definite shape
thousands of years ago, and received a solid mathematical foundation.
Observations of the movements of the planets and eclipses of the
sun were conducted by the Chinese, Chaldeans, and Egyptians several
thousand years before Christ. Christ himself had no more suspicion of
these great cosmological discoveries than of the systems which the
Greek natural philosophers had built up three hundred to six hundred
years before his birth. After Copernicus had destroyed the geocentric
system in 1543, and Newton had provided a mathematical basis for
the new heliocentric system by his theory of gravitation in 1686,
cosmogony was firmly established in a monistic sense by the _General
Natural History of the Heavens_ of Kant, and the _Mécanique Céleste_ of
Laplace. Since that time there has been no question of the conscious
action of a Creator in any part of astronomy. Astrophysics has enlarged
our knowledge of the physical features, and astrochemistry (by means
of spectrum analysis) of the chemical nature of the other heavenly
bodies. The monism of the physical universe has now been established.

Geology was not developed into an independent science until towards
the end of the eighteenth century, and did not extinguish the earlier
notion of the creation of the earth until after 1830, when the
principle of continuity and evolution was established. The oldest
part of the science is mineralogy; the great practical value of the
rocks, and especially the metals obtained from them, having appealed to
man's interest thousands of years ago. In the Stone Age, Bronze Age,
Iron Age, etc., the material for weapons and tools was provided by
stone and metal. Afterwards the development of mining led to a closer
acquaintance with these metals. But no notice was taken of the fossil
remains of animals and plants until the close of the Middle Ages. It
was not until the eighteenth century that students began to perceive
the great significance of these "creation-medals," and at the beginning
of the nineteenth paleontology arose as an independent science, and
proved equally important to geology and biology. Other branches of
geology, such as crystallography, have also made considerable progress
during the last half-century, with the aid of physics and chemistry.
All these sections of geology, especially geogeny, or the science of
the natural development of the earth, are now recognized to be purely
monistic sciences.

In the five branches of science I have enumerated, pure monism has
been universally and exclusively admitted (as far as they relate to
inorganic nature) in the second half of the nineteenth century. There
is no question in them to-day of the wisdom and power of the Creator.
This is equally true of geology, astronomy, mathematics, chemistry,
and physics. It is otherwise with the remaining sciences which deal
with organic nature; in these we have not yet succeeded in giving a
physical explanation and mathematical formulation of all phenomena.
Hence vitalism enters with its dualistic notions, and splits the
science into two different branches--natural science (physics in the
wider sense) and mental science (metaphysics); fixed natural laws are
supposed to rule only in the former, while in the latter we still have
the "freedom" of the spirit and the supernatural. This applies, first
of all, to biology in the broadest sense (including anthropology and
all the sciences that relate to man). In the preceding chapters of
biological philosophy we have sought to refute vitalism in every form,
and to secure the exclusive acceptance of monism and mechanicism in
every branch of the science of life.

Anthropology is still, as it has been for centuries, taken in many
different senses. In the widest sense, it embraces the whole vast
science of man, just as zoology (in my opinion) deals with all
parts of the animal world. Since I regard anthropology as a part
of zoology, I naturally extend the principles of monism to both.
However, this general monistic conception of the science of man has
met with only a restricted acceptance up to the present. As a rule,
the term "anthropology" is restricted to the natural history of man,
which includes the anatomy and physiology of the human organism,
embryology, prehistoric research, and a small part of psychology. But
this "official anthropology," as most of our anthropological societies
(especially in Germany) conceive it, generally excludes phylogeny, the
greater part of psychology, and all the mental sciences, which are
regarded as metaphysical in the narrower sense. I endeavored to show in
my _Anthropogeny_ thirty years ago that man (as a placental mammal of
the order of primates) is no less unified an organism (with body and
soul) than any other vertebrate, and that, therefore, every aspect of
his being should be dealt with monistically.

As is well known, the views of experts and laymen alike are very much
divided as to the place of psychology in the scheme of the sciences.
The great majority of the professional psychologists, and of educated
people generally, adhere still to the antiquated dogma, with its
religious foundation, that man's soul is immortal and an independent
immaterial entity. This dualistic view has been supported in the
schools especially by the authority of Plato, Descartes, and Kant; in
religion by the authority of Christ, Paul, and Mohammed; in education
and the state by the authority of most governments; and in physiology
by most of the older, and even some recent, physiologists. On this
view, psychology is a special mental science, having only an external
and limited connection with natural science. But modern comparative
and genetic psychology, the anatomy and physiology of the brain,
have, in the course of the last forty years, established the monistic
view that psychology is a special branch of cerebral physiology, and
that therefore all its parts and their application belong to this
section of biology. The soul of man is a physiological function of
the phronema. As I have fully explained the monistic conception of
psychology in chapters vi.-xi. of the _Riddle_, and supported it with
all the arguments of anatomy, physiology, ontogeny, and phylogeny in my
_Anthropogeny_, I need not go further into the subject.

The science of language shares the fate of its sister, psychology;
by one section of its representatives it is taken monistically as a
natural science, and by another section it is dualistically conceived
as a branch of mental science. On the old metaphysical view, speech was
regarded as an exclusive property of man, either a gift of the gods or
an invention of social man. But in the course of the nineteenth century
the monistic and physiological position that speech is a function
of the organism, and has been gradually developed like all other
functions, has been established. The comparative psychology of the
higher animals showed that in various classes the thoughts, feelings,
and desires of the gregarious animals are communicated partly by signs
or touch, partly by sounds (the chirrup of the cricket, the cry of the
frog, the whistle of many reptiles, song of birds and singing-apes,
roaring of carnivora and ungulates, etc.). The ontogeny of speech
showed that its gradual development in the child is (in accordance
with the biogenetic law) a recapitulation of its phylogenetic process.
Comparative philology taught that the languages of the different races
have been formed polyphyletically, or independently of each other.
The experimental physiology and pathology of the brain showed that a
definite small region of the cortex (the Broca fissure) is the centre
of speech, and that this central organ, in conjunction with other
parts of the phronema and the larynx (the peripheral organ), produces
articulate speech.

Historical science is, like philology or psychology, still conceived
in different senses by experts. Very often history is wrongly taken
to mean the record of events that have occurred in the course of the
development of civilized life--the history of peoples and states
(humorously described as "the history of the world"), of civilization,
of morals, etc. This is merely an anthropocentric feeling that in
the strictly scientific sense "history" can only be used for the
record of man's doings. In this sense history is opposed to nature,
the one dealing with the province of morally free phenomena (with
preconceived aim), and the other comprising the province of natural
law (without preconceived aim). As if there were no "natural history,"
or as if cosmogony, geology, ontogeny, and phytogeny were not
historical sciences! Although this dualistic and anthropistic view
still prevails in our universities, and state and Church protect the
venerable tradition, there can be no doubt that sooner or later it
will be replaced by a purely monistic philosophy of history. Modern
anthropogeny shows us the intimate connection between the evolution of
the human individual and that of the race; and by means of prehistoric
and phylogenetic research it joins what is called the history of the
world to the stem-history of the vertebrates.

Medicine belongs to the front rank of practical or applied sciences. In
its long and interesting history it teaches how it is only a monistic
knowledge of nature, not a dualistic notion of revelation, that affords
the foundations of true science and the profitable application of
this to the most important aspects of practical life. Medicine was
originally the business of the priests, and for thousands of years
it was under the influence of mystic and superstitious ideas which
were connected with religious dogmas. However, two thousand years ago
the great physicians of classic antiquity made a serious effort to
provide a solid base for medical practice by a thorough anatomic and
physiological study of the human frame. But in the general reaction
of the Middle Ages superstitious and miraculous ideas once more
defeated independent scientific investigation. Disease was supposed
to be the work of evil spirits (as Christ thought) which had to be
exorcised. Miracles are still thought to take place, even in cultured
circles. I need only mention the wonders of patent medicines, magnetic
cures, Christian Science, and other charlatanry. However, the great
development of science in the nineteenth century, especially the
astonishing advance of biology about the middle of the century,
gradually shaped medicine into the monistic science which assuages so
much pain and suffering in humanity to-day. Pathology, the science
of disease, and therapeutics, the rational science of healing, are
grounded now on the safe methods of physics and chemistry and a
thorough knowledge of the human organism. Disease is no longer regarded
as a special entity that comes on the body like an evil spirit or
mysterious organism, but is conceived as a baneful disturbance of its
normal activity. Pathology is only a branch of physiology; it studies
the changes that take place in the tissues and cells under abnormal and
dangerous conditions. When the causes of these changes are poisons or
foreign organisms (such as bacteria or amœbæ), the art of healing
has to remove them and restore the normal equilibrium of the functions.

The science of mental disease is a special branch of medicine; it has
the same relation to it as psychology has to physiology. However, as
pathological psychology it deserves special consideration, not only
on account of its extreme practical importance, but also because of
its theoretical interest. The misleading dualist idea of body and soul
that has perverted our notions of mental life from the oldest times
has led people to regard mental disorders as special phenomena, at one
time directly as evil spirits that enter from without into the human
body, at another time as mysterious dynamic occurrences affecting the
mystic being of the soul (independently of the body). These dualistic
and still wide-spread and mischievous errors have caused the most
fatal mistakes in the treatment of mental disease; they have had the
most unfortunate effect on juristic and social and other aspects of
practical life. But the ground has been cut from under these irrational
and superstitious ideas by modern psychiatry, which regards all mental
disease as a disorder of the brain, and traces it to changes in the
cortex that lie at the root of all psychoses (delusions, lunacy,
etc.). As we call this central organ of mind the phronema, we may say:
Psychiatry is the pathology and therapeutics of the phronema. In many
disorders we have already succeeded in anatomically and chemically
tracing the changes in the psychic or phronetal cells (the neurona
in the phronema). These acquisitions of the pathological anatomy and
physiology of the phronema have a great philosophic interest, because
they throw a good deal of light on the monistic conception of psychic
life. As the greater part (sixty to ninety per cent.) of these diseases
are hereditary, and they have mostly been acquired gradually by the
ancestors of the patient, they also afford clear proof of progressive
heredity, or the inheritance of acquired characters.

Thousands of years ago, when barbaric races began to adapt themselves
to civilized life, they had a concern for their bodily health and
strength. In classic antiquity the care of the body by baths, gymnastic
exercises, etc., was greatly developed, and connected with religious
ceremonies. The splendid aqueducts and baths of Greece and Rome show
how much importance they attached to the external and internal use of
water. The Middle Ages brought reaction in this province like so many
others. As Christianity depreciated this life and said it was merely a
preparation for the life to come, it led to a disdain of culture and
of nature; and as it regarded man's body only as the temporary prison
of his immortal soul, it attached no importance to the care of it. The
frightful plagues that swept away millions of men in the Middle Ages
were only fought with prayer, processions, and other superstitious
devices, instead of with rational hygienic and sanitary measures. We
have only gradually learned to discard this superstition. It was not
until the second half of the nineteenth century that a sound knowledge
of the physiological functions and environment of the organism induced
people once more to have a concern for bodily culture. All that modern
hygiene now does for the public health, especially the improvement of
the dwellings and food of the poorer classes, the prevention of disease
by healthier habits, baths, athletics, etc., can be traced to the
monistic teaching or reason, and is altogether opposed to the Christian
belief in Providence and the dualism connected therewith. The maxim of
modern hygiene is: God helps those who help themselves.

The remarkable progress of technical science in the nineteenth
century, which has stamped our age as "an age of machinery," is a
direct consequence of the immense advance of theoretical science.
All the privileges and comforts which modern life gives us are due
to scientific discoveries, especially in physics and chemistry.
We need only recall the enormous importance of steam and electric
machinery, modern mining, agriculture, and so on. If by these means
modern industry and international commerce have prospered beyond all
expectations, we owe this to the practical application of empirical
truths. "Mental science" and metaphysical speculation have had nothing
to do with it. There is no need of further proof that all the technical
sciences have a purely monistic character, like their exact sources,
physics and chemistry.

The scientific development of education is one of the greatest tasks
of modern civilization. The ideas that are impressed on the mind in
early youth are most persistent, and generally determine the direction
of thought and conduct for the whole of life. Hence we find the
struggle between the two philosophic tendencies assuming the greatest
practical importance in this department. As the priests were, thousands
of years ago, in the first stages of civilization, the sole trainers
of the growing mind, they had charge of the school as well as of
medicine. Religion was made the chief foundation of instruction, and
its doctrines were the moral guide for the whole of life. The isolated
attempts that were made by monistic philosophy in ancient times to
destroy this theistic superstition had no effect on the education of
the young. In this the dualistic principles of Plato and Aristotle
prevailed, their metaphysical theories being blended with the teaching
of the Church. In the Middle Ages the power of the Roman priesthood
enforced them everywhere. And, although a good deal of this teaching
lost its prestige at the Reformation, the influence of the Church on
the school was maintained down to our own time. The spiritual power of
the Church finds a useful ally in this in the conservative attitude
of most governments. Throne and altar support each other; both dread
the advance of scientific inquiry. In face of this powerful dualistic
alliance, supported by the mental apathy of the masses and a convenient
blind submission to authority, the monistic system has a difficult
position to maintain. It will only gain solid ground in education when
the school is divorced from the Church and scientific knowledge is made
the foundation of the curriculum. I have pointed out in the nineteenth
chapter of the _Riddle_ the guiding principles to be followed in this
reform of education in opposition to the influence of Church and state.

As we have dealt in the eighteenth chapter with morals and their
development from habit and adaptation, we need only mention here the
contradiction that we still find between the monistic claims of pure
reason and the dualistic claims of practical reason. This has been
largely sustained by Kant's teaching, but his categorical imperative
has been completely refuted by modern science. The metaphysical
grounding of morality on free will and ethical intuitions (_a
priori_) must be replaced by a physiological ethic, based on monistic
psychology. As this can no more recognize a moral order of the world
in history than a loving Providence in the life of the individual,
the monistic morality of the future must be reducible to the laws of
biology, and especially of evolution.

The great importance that attaches to the new science of sociology is
due to its close relations to theoretical anthropology and psychology
on the one hand, and to practical politics and law on the other. When
we take it in the wider sense, human sociology joins on to that of
the nearest mammals. The family life, marriage, and care of the young
in the mammals, the formation of herds in the carnivora and ungulates
and of troops in the social apes, lead on to the looser associations
of savages and barbarians, and from these to the beginnings of
civilization. The history of these associations is connected with
the social rules that govern the intercourse of smaller and larger
communities. In the biological reduction of social rules to the natural
laws of heredity and adaptation, dynamic sociology (as Lester Ward
has called it) proceeds on purely monistic lines, while in social
intercourse itself we still find a good deal of dualism. How little
truth and nature count for in our cultured society, how much hypocrisy
and insincerity have to do with social rules, has been well shown by
Max Nordau in his _Conventional Lies of Civilization_.

Politics is closely connected with sociology on the one hand and
law on the other. As internal politics it controls the organization
of the state by a constitution; as external or foreign politics it
directs the relations of states to each other. In my opinion, pure
reason should prevail in both departments; the relations of the
citizens to each other and to the whole should be regulated by the
same ethical principles that we recognize in personal intercourse. We
are, unfortunately, very far from this ideal in the life of a modern
state. Brutal egoism rules in foreign politics; every nation thinks
only of its own advantage, and furthers it with all its military and
other resources. Domestic politics is still largely directed by the
barbaric prejudices of the Middle Ages. Great struggles are in progress
between the central government and the mass of the people. Both parties
spend themselves in fruitless conflicts; yet reason in the life of the
state suffers more than its special political complexion. "Whether the
state shall be a monarchy or a republic, aristocratic or democratic,
are subordinate questions. The great question is: Shall the modern
state be spiritual or secular? Shall it be governed _theocratically_ by
irrational beliefs and clerical arbitrariness, or _nomocratically_ by
rational laws and civic right?" (_Riddle_, chapter i.).

In the science of law, too, we find the prevalence of the dualistic
principles that have come down from the Middle Ages and antiquity, and
have acquired a certain sacredness by blending with the teaching of
the Church. Kant's dualism is again found to be at work, influencing
the ideas of jurists and statesmen. With it we find in our codes many
carefully preserved relics of mediæval superstition. A great deal of
harm is done by this religious influence. Every day we read in the
papers of curious deliverances in the lower and higher courts at which
every thoughtful man can only shake his head. Here also there will be
no solid improvement until the education of jurists includes a thorough
training in anthropology and psychology as well as in the code.

Theology has stood at the head of the four venerable "faculties" at
our universities for centuries. It still holds this place of honor,
as the Church, the organ of practical theology, continues to exercise
a profound influence on life. In fact, most of the other branches
of applied science--especially jurisprudence, politics, ethics, and
pedagogics--are still more or less affected by religious prejudices.
The chief of these is the idea of God conceived in some form or other
as the Supreme Being; as Goethe says, "Every one calls the best he
knows his God." However, the idea of God is not the chief feature
of all religions. The three greatest Asiatic religions--Buddhism,
Brahmanism, and Confucianism--were at first purely atheistic; Buddhism
was at once idealistic and pessimistic, whence Schopenhauer regarded
it as the highest of all religions. On the other hand, belief in a
personal God is the central feature of the three great Mediterranean
religions. This anthropomorphic God is conceived in a hundred forms in
the various sects of the Mosaic, Christian, and Mohammedan religions,
but his existence remains one of the chief articles of faith. No
evidence of his existence is to be found; this was very ably shown by
Kant, although he thought that practical reason postulated it. All that
revelation is supposed to teach us on the matter belongs to the region
of fiction. The whole field of theology, especially dogmatic theology,
and the whole of the Church teaching based on it, are based on
dualistic metaphysics and superstitious traditions. It is no longer a
serious subject of scientific treatment. On the other hand, comparative
religion is a very important branch of theoretical theology. It deals
with the origin, development, and significance of religion on the
basis of modern anthropology, ethnology, psychology, and history. When
we study without prejudice the results of these sciences bearing on
religion, theology turns out to be pantheism, in the sense of Spinoza
and Goethe, and thus monism becomes a connecting link between religion
and science.

This brief survey of the twenty chief branches of modern science
and their relation to monism and dualism shows that we are face to
face with great contradictions, and that we are still far from the
harmonious and successful adjustment of these differences. They are
partly due to a real antinomy of reason in the Kantist sense--an
antithesis in ideas, in which the positive seems to be just as
capable of proof as its contradictory. But, for the most part, this
unfortunate antinomy in the sciences is connected with their historical
development. Pure reason, the highest quality of civilized man, was
gradually evolved from the intelligence of the savage, and this in turn
from the instincts of the apes and lower mammals; and many relics of
its former lower condition remain to-day, and have, through practical
reason, a most prejudicial influence on science. These dualistic
prejudices and irrational dogmas--intellectual residua of the primitive
condition of the race, fossil ideas and rudimentary instincts--still
pervade the whole of modern theology, jurisprudence, politics, ethics,
psychology, and anthropology. If we glance at the whole field of modern
science at the beginning of the twentieth century in this connection,
we can distribute its twenty sections into three groups--rational
(purely monistic), semi-dogmatic (half-monistic), and dogmatic
(predominantly dualistic) disciplines.

The following may be classed as rational or purely monistic sciences,
in which no competent and thoroughly expert representative now admits
dualistic considerations: of the pure or theoretical sciences, physics,
chemistry, mathematics, astronomy, and geology; of the applied or
practical sciences, medicine, hygiene, and technology. On the other
hand, in the semi-dogmatic sciences we still find a mixture of
monistic and dualistic ideas in the appreciation of their aims and
objects, one or the other prevailing according to the party position
or personal training of the individual representative. This is the
case with most of the biological sciences, biology (in the broadest
sense), anthropology, psychology, philology, history, psychiatry;
and of the applied sciences, pedagogics and ethics. The two latter
sciences form a transition to the four purely dogmatic sciences in
which the traditional dualism is still paramount: sociology, politics,
jurisprudence, and theology. In these branches of science mediæval
traditions retain a good deal of their power. Most of their official
representatives cling to prejudices and superstitions of all sorts,
and very slowly and gradually admit the acquisitions of pure reason as
embodied in monistic anthropology and psychology. The intellectual life
was in many respects more advanced at the beginning of the nineteenth
than of the twentieth century.

This classification of the chief branches of knowledge in their
relation to philosophy, the comprehensive science of general truths,
is naturally only a provisional and personal sketch. It is especially
difficult from the circumstance that all the sciences have very complex
relations to each other, and have undergone many changes as to their
aims and subjects in the course of their historical development. I
will only point out that a good deal of science--in fact, the rational
sciences with exact mathematical basis--have now been completely won
over to monism; and in the semi-dogmatic sciences it is gaining ground
from day to day, so that we may hope sooner or later to see the four
dogmatic sciences also, the strong bulwarks of dualism--sociology,
politics, jurisprudence, and theology--succumb to monism. For the
ultimate aim of all the sciences can only be the unity of their
underlying principles, or their harmonious unification by pure reason.

It is now more and more generally acknowledged in educated countries
that a complete reform of our educational curriculum is needed,
both in elementary and secondary schools and at the universities.
The great struggle between two different tendencies assumes larger
proportions every day. On the one hand, most governments, following
their conservative instinct, cling as far as possible to mediæval
traditions, and find support in the dogmatic teaching of theology
and jurisprudence. On the other hand, the representatives of pure
reason seek to get rid of these fetters, and to introduce the
empirical and critical methods of modern science and medicine into
what are called the mental sciences. The opposition between the two
parties is accentuated by their different sociological tendencies.
Liberal humanists claim that the freedom and education of all men is
the aim of progressive evolution, in the conviction that the free
development of the personality of each individual is the surest
guarantee of happiness. To conservative governments this is a matter of
indifference; they look on the individual citizens, in accordance with
the manifold division of labor, merely as so many screws and wheels in
the great organism of the state. The "upper ten thousand" naturally
think of their own welfare first, and desire to keep all higher
education to themselves. But in the light of pure reason the state is
not an end in itself; it is a means to insure the prosperity of the
citizens. To each of these, whatever their condition, the opportunity
should be afforded of acquiring the higher education and developing
their talents. Hence in education we should impart a general outlook
on all the sides of human life. Each should acquire the elements of
science, not only of physics and chemistry, but also of biology and
anthropology. On the other hand, the predominance of the classical
training over modern ought to be restricted. Every student and every
faculty should be occupied with only philosophy and science in the
first sessions, and not take up special studies until afterwards.

At the close of the _Riddle_ I brought out in clear relief the
antagonism between modern monism and traditional dualism, but also
pointed out that

 this strenuous opposition may be toned down to a certain degree
 on clear and logical reflection--may, indeed, be converted into a
 friendly harmony. In a thoroughly logical mind, applying the highest
 principles with equal force in the entire field of the cosmos--in
 both organic and inorganic nature--the antithetical positions of
 theism and pantheism, vitalism and mechanism, approach until they
 touch each other. Unfortunately, consecutive thought is a rare
 phenomenon in nature.

This conciliatory disposition has grown stronger and stronger in
me. Every year increases my belief that the dualism of Kant and the
prevalent metaphysical school must give way to the monism of Goethe and
the rising pantheistic tendency. In this we do not lose sight of our
ideals. On the contrary, our "realist philosophy of life" teaches us
that they are rooted deep in human nature. While occupying ourselves
with the ideal world in art and poetry, and cultivating the play of
emotion, we persist, nevertheless, in thinking that the real world,
the object of science, can be truly known only by experience and pure
reason. Truth and poetry are then united in the perfect harmony of
monism.




INDEX


  Abiogenesis, 339-358;
    may still occur, 357.

  Abiology, 27, 78.

  Abortion, 325.

  Abstraction, power of, 316.

  Achromin, 140, 142.

  Acquired characters, inheritance of, 367-369, 376.

  Actinal beauty, 185.

  Active movements in organisms, 262.

  Adaptation, 415.

  Æsthesis, 296, 308.

  Æsthetal cells, 14.

  Æsthetic selection, 422.

  Agassiz on the creation of species, 30.

  Agnostic position on the origin of life, 338.

  Albumin, 39, 126, 128.

  Albuminoids, the, 39, 125, 126.

  Algæ, 161, 195, 220.

  Alimentary system, the, 227.

  Allopola, 174.

  Alternation of generations, 253.

  Altmann on the structure of plasm, 134.

  Altruism, sources of, 115.

  Ambulacral system, 280.

  Amœboid movements, 268.

  Amphigony, 240.

  Amphimixis, 244.

  Amphithecta, 176.

  Angiophyta, 220.

  Animal states, 36, 148, 150, 168.

  Animals, kindness to, 115;
    younger than plants, 216.

  Animism, 58.

  Annelids, motor apparatus of the, 281.

  Antheridia, 249.

  Anthophyta, 162, 220.

  _Anthropogeny, The_, 283, 320.

  Anthropogeny, the science of, 321, 332.

  Anthropologists and evolution, 321.

  Anthropology, 86, 478.

  Antivitalism, 50.

  Ape, mind in the, 332, 333.

  Apes and men, common structure of, 285.

  Aphanocapsa, 32, 130, 182, 196, 205.

  Apostles' Creed, the, 60-65.

  Apotelia, 163.

  Apposition, 42.

  Archegonia, 249.

  Archigony, 341-358;
    formulation of, 355, 356;
    repetition of, 356;
    statement of grounds, 341;
    theories of, 343-348.

  Archiplasm, 129, 142, 158.

  Aristotle, 66.

  Art, modern development of, 407.

  Articulates, motor apparatus of the, 282.

  Articulation, 281.

  Asexual generation, 241-244.

  Assimilation, 42, 211.

  Association-centres, 12, 13.

  Associational beauty, 185.

  Astrolarva, 279.

  Astronomy, monism of, 457.

  Astrozoon, 280.

  Asymmetrical types, 179.

  Auditory vesicles, 311.

  Autogony, 341.

  Autonomous movement, 262.


  Bacilli, 200, 201, 202.

  Bacon, the founder of empiricism, 7.

  Bacteria, the, 157, 198-206, 218, 234, 235;
    absence of nucleus in the, 200, 201.

  Bacteriology, 198.

  Baptism, 425, 426.

  Barbarians, higher, 395;
    life of, 394;
    lower, 394;
    mental life of, 58;
    middle, 395;
    religion of, 58.

  Baræsthesis, 309.

  Barotaxis, 309.

  Bathybius Haeckelii, 207.

  Beauty, evolution of the sense of, 188;
    sources of, 184;
    stages of, 184-187.

  Beggiatoa, 199, 205, 218.

  Berzelius on catalysis, 44.

  Bilateral-radial types, 177.

  Bilateral symmetry, 177.

  Bioblasts, 134.

  Bio-crystals, 41.

  Biogen-hypothesis of Verworn, 46, 137, 138.

  Biogens, 102, 128, 137, 192.

  Biogenetic law, the, 380-382, 384.

  Biogeny, 94, 360.

  Biology, division of, 94;
    sphere of, 27, 78.

  Bionomy, 78, 95.

  Bionta, 149, 151;
    virtual, 151;
    partial, 151.

  Biophora, 137.

  Biotonus, 103.

  Blastoderm, the, 161.

  Botanists and zoologists, divergence of, 374.

  Brain, as an organ of mind, 25;
    evolution of the, 22, 327, 328.

  Brownian movement, 260.

  Bryophyta, 162.

  Budding, 242, 243.

  Bunge, as vitalist, 50.

  Bütschli on the monera, 31;
    on the structure of plasm, 132.


  Calymma, the, 270.

  Canon law, the, 324, 325.

  Carbon assimilation, 34, 130, 212, 213, 342.

  Carbon, importance of, 37, 38.

  Caryokinesis, 139, 267.

  Caryolymph, 141, 142.

  Caryolysis, 268.

  Child, mind of the, 90, 323.

  Child-soul, study of the, 20.

  Children, destruction of incurable, 21, 120.

  Chitine, 282.

  Chlorophyll, 33, 141, 195, 214.

  Chorology, 95.

  Chromacea, 32, 130, 137, 157, 182, 194-197;
    description of the, 194;
    structure of the, 197.

  Chromatella, 33, 343.

  Chromatin, 140, 142.

  Chromatophora, 33, 343.

  Chromoplasts, 141, 196.

  Chroococcacea, the, 32, 182.

  Chroococcus, 32, 130, 182, 196, 197, 208.

  Ciliary movement, 272, 276.

  Circulation of the blood, 228.

  Civilization, characteristics of, 58-59;
    evils of, 114;
    growth of, 334;
    modern, 335, 402;
    shades of, 401, 408;
    stages of, 398;
    progress of, 469;
    value of, 309.

  Civilized races, higher, 397;
    life of, 396;
    lower, 396;
    middle, 396;
    mind in, 334.

  Cleanliness in antiquity, 464.

  Clothing, beginning of, 423;
    fashions in, 430.

  Cnidaria, 224;
    generation of the, 250, 253.

  Cœlenteria, 166, 221, 223, 225.

  Cœloma, the, 223, 225.

  Cœlomaria, 166, 221, 225.

  Cœnobia, 160, 161.

  Colloids, nature of, 39.

  Colon, the, 226.

  Coloring methods, 208.

  Conjugation, 246.

  Consciousness a function of the brain, 331;
    development of, 331;
    nature of, 19, 23, 290, 291.

  Conservatism of governments, 73.

  Contact-action, 45.

  Copulation, 251.

  Cormophyta, 165, 167.

  Cormus, 36, 148, 150, 154, 168, 184.

  Corset, the, 430.

  Cortex of the brain, 12, 323, 327, 329.

  Cosmic intelligence, 30;
    monism, 37.

  Cosmogony, 360.

  Cosmokinesis, 266.

  Craniota, mind in the, 326.

  Creationism, 337.

  Crustacea, parasitic, 237.

  Crystals, 41;
    forms of, 172;
    growth of, 42, 43;
    life of, 41;
    and organisms compared, 35, 40, 41, 43, 44;
    reproduction of, 44.

  Crystallization, 265, 266.

  Crystalloids, nature of, 39.

  Culmus, the, 165, 183.

  Cultivated races, definition of, 397;
    higher, 400;
    lower, 398;
    middle, 399.

  Custom, tyranny of, 421.

  Cuticle, 146.

  Cyanogen, 346.

  ---- theory, 347.

  Cytodes, 33, 157, 192, 194.

  Cytology, 128, 190.

  Cytophyta, 220.

  Cytoplasm, 35, 122, 138, 139, 142, 158, 191.

  Cytosoma, 122, 138.

  Cytotheca, 145.

  Cytula, 244.


  Darwin on the origin of life, 338.

  Darwinism, 50, 80, 361, 363, 364, 373.

  De Bries on heredity, 373.

  Death, nature of, 98;
    of the unicellulars, 99;
    of the histona, 100;
    real cause of, 101;
    total and partial, 105.

  Decomposability of plasm, 345.

  Descartes' idea of the soul, 16, 18.

  Descriptive science, 4, 5, 6.

  Design, argument for, 388.

  Dialysis, 39.

  Diatomes, 41, 182.

  Diclinism, 247.

  Diœcia, 248.

  Disassimilation, 212.

  Disease, nature of, 106.

  Dissogony, 252.

  Division of labor, 35;
    in the cell, 143, 158;
    in the organism, 149, 167;
    in the state, 150, 169.

  Divorce, 428, 429.

  Dogmatic sciences, 470.

  Dominants, the, of Reinke, 264.

  Driesch, as vitalist, 51.

  Dualism, 81, 91, 433.

  Dualistic view of life, 337, 348, 366;
    of the mind, 332;
    of morality, 411;
    of sensation, 446, 447.

  Dumas, Louis, as vitalist, 47.

  Duty an evolved sense, 413.

  Dwarf races, 422.

  Dynamism, 85, 110.


  Ear, canals in the, 311;
    the, 312.

  Echinoderms, motor organs of the, 279-281.

  Ectogenesis, 369.

  Education, reform of, 471;
    struggle over, 465.

  Egoism, 115, 403;
    and altruism, 419.

  Elasticity, 310.

  Eleatic philosophers, the, 66.

  Electric organs, 313.

  Electricity, sensation of, 312, 313.

  Elements, chemical, 37, 38.

  Embryo, legal view of the, 325, 326;
    mind in the, 325.

  Embryology, 20, 21;
    mechanical, 383.

  End of life, 387.

  Energism, 85.

  Energy as attribute of substance, 446, 449;
    definition of, 449.

  Enzyma, 46, 128.

  Epicureanism, 83.

  Epitelia, 163.

  Epithelium, ciliated and flagellated, 276.

  Erect posture, the, 285.

  Ergology, 95.

  Ergonomy, 35, 150.

  Erotic chemotropism, 306.

  Eternity hypothesis of life, 338.

  Ethic, the perfect, 400.

  Ethics, 411.

  Eucharist, the, 426.

  Excretion, 232, 233.

  Experience, importance of, 3, 4.

  Experiment, limited use of, 352, 353, 383;
    nature of, 7, 8.

  Experimental science, 4, 8.

  Extension, 446, 448.

  Eye, the, 298;
    evolution of, 298, 299.


  Faith, 437, 439;
    natural and supernatural, 54.

  Family, evolution of the, 402.

  Fashion, 422.

  Fechner on sensation, 295;
    on the universality of life, 340.

  Feeling, 296, 308.

  Fetichism, 57, 58.

  Filar theory of plasm, 134.

  Fistella, 344.

  Flagelliform movement, 271, 276.

  Flame, analysis of the, 28.

  Flat-fishes, metamorphosis of, 178.

  Flechsig, discoveries of, 13.

  Flemming on the structure of plasm, 113.

  Food, artificial production of, 400.

  Forms of organic structure, 173-184.

  Frommann on plasm, 133.

  Frothy theory of plasm, 132, 133.

  Fungi, 162, 204, 215, 234, 236.

  Fungilli, 204, 235.


  Gameta, the, 244.

  Gastræa theory, the, 223.

  Gastræads, 223.

  Gastric canal, 228.

  Gastro-canal system, 222, 223.

  Gastrula, the, 166.

  Gemmation, 242, 243.

  Genealogy of organisms, 304, 305, 376.

  Generation, sexual and asexual, 241-251.

  Geogeny, 360.

  Geology, historical nature of, 378;
    monism of, 458.

  Geotropism, 310.

  Germ-plasm, 143;
    the theory of, 367, 372.

  German mind, Janus character of, 441.

  Gills, 229, 230.

  Globular shape, origin of, 34.

  Glœocapsa, 32, 196, 205.

  Goethe, monism of, 442;
    realism of, 440;
    scientific studies of, 440, 441.

  Gonades, 249.

  Gonochorism, 246.

  Gonoducts, 250.

  Granular theory of plasm, 134.

  Gravitation, sensation in, 309.

  Growth, 241.

  Growth movements, 264.


  Habit, 415-417;
    in inorganic bodies, 417.

  Heart, the, 228;
    work of the, 277.

  Heat, sensation of, 300, 301.

  Heaven, 109.

  Hedonism, 84.

  Heliotropism, 298.

  Helmholtz on the origin of life, 339.

  Heraclitus on life, 28.

  Heredity, conservative and progressive, 368;
    cumulative, 369;
    theories of, 135, 136, 366.

  Hermaphrodism, 245, 246, 258, 259.

  Hermaphroditic glands, 249.

  Hertwig, O., on the biogenetic law, 382;
    on the monera, 31.

  Heterogenesis, 254.

  His, W., theories of, 383.

  Histolysis, 106.

  Histona, the, 36.

  Histonals, 165, 166, 171, 182.

  Historical waves, 389.

  History, 461;
    nature of, 9;
    sources of, 9.

  Hofmeister on organic chemistry, 45.

  Holosphæra, 173.

  Honor, false sense of, 430.

  Huxley on organic individuality, 152.

  Hyaloplasm, 130, 143.

  Hybrids, 255, 256;
    fertility of, 255.

  Hydrostatic movements, 270.

  Hygiene, 401, 464.

  Hylonism, 82.

  Hylozoism, 81, 86, 451.

  Hypogenesis, 255.

  Hypotheses, nature of, 54;
    necessity for, 86, 87, 89, 378, 439.


  Idealism, theoretical and practical, 84, 92.

  Idiocy, 20.

  Idioplasm theory, the, 136, 137, 366, 367.

  Ileum, the, 226.

  Imagination, function of the, 87.

  Imbibition energy of plasm, 39.

  Imbibition in organisms, 261.

  Immaterial world, the, 436, 437.

  Immortality, the belief in, 64, 65, 71, 108;
    of the unicellulars, 99-101.

  Incurables and suicide, 118, 119.

  Individuality, organic, 149, 152.

  Infusoria, movement in the, 268, 269, 272.

  Inoculation, 204.

  Insanity, increase of, 114, 118, 119.

  Insectivorous plants, 304, 305.

  Instinct, 418.

  Intelligence, 316, 317.

  Intercellular matter, 145.

  Intussusception, 42.

  Ionic philosophers, the, 66.

  Irritability, 287, 288, 291, 293.

  Isopola, 174.


  Kant as natural historian, 9;
    biological ignorance of, 11, 318, 319;
    critical views of, 438;
    contradictory views of, 68, 434, 444;
    influence of, 25;
    mechanical views of, 435;
    moral philosophy of, 412, 413;
    mystic training of, 443;
    narrow life of, 443;
    philosophy of, 68, 69, 74, 434-440;
    popularity of, 444;
    theory of knowledge of, 9, 10, 69, 317-319, 332.

  Kassowitz on archigony, 355.

  Kelvin, Lord, on the origin of life, 339.

  Kidneys, the, 233.

  Kirchhoff on the work of science, 6.

  Knowledge, _a priori_ and _a posteriori_, 11, 24, 317;
    and faith compared, 54;
    dualistic
    theory of, 24;
    monistic theory of, 12-14.

  Kusamaul on the child-soul, 30.


  Lamarck, 79.

  Lamarck's transformism, 363.

  Landscape beauty, 187.

  Lange on Kant, 439.

  Larvæ, 253.

  Law, beginning of idea of, 420;
    reaction in science of, 401.

  Leibnitz, philosophy of, 110.

  Leucocytes, 228;
    and bacteria, 305.

  Lichens, 238.

  Life, artificial production of, 352, 358;
    as a flame, 28, 29;
    constant change of, 386, 387;
    evolution of, 360-365;
    length of, 101;
    nature of, 27, 343;
    origin of, 337-358;
    value of, 386-410.

  Light, action of, 297-300.

  Living substance, 36, 123.

  Lobmonera, 206.

  Localization of functions, 17, 19, 20;
    of mental functions, 328, 329.

  Locomotion, 275-285;
    modern progress in, 404.

  Lord's Supper, the, 426.

  Love, progressive refinement of, 402.

  Luminous animals, 312.

  Lungs, 230, 231.


  Machine-theory of life, the, 29, 30, 102.

  Macrogameton, 244.

  Mammals, common descent of the, 284;
    motor apparatus of the, 283.

  Manners and morals, 421.

  Marriage, development of, 402, 403;
    evolution of, 427;
    priestly control of, 428.

  Materialism, 82, 451.

  Mathematics, 456.

  Matrimony, 427, 428.

  Matter as attribute of substance, 448.

  Mechanical embryology, 103.

  Mechanics, 259.

  Medicine, development of, 462.

  Membranes, cellular, 144, 145, 155, 157, 194.

  Memory, 416.

  Mental disease, evidential value of, 19.

  Metabolism, 28,38, 44, 46, 103, 130, 210, 211, 217;
    a mechanical process, 259, 260;
    in the metaphyta, 219-221;
    in the metazoa, 221, 233;
    in the protophyta, 217-219;
    in the protozoa, 219, 220.

  Metagenesis, 253.

  Metamerism, 167, 168, 281.

  Metamorphology, 94.

  Metaphysicians disdain physical science, 16.

  Metaphysics, nature of, 10, 88, 89.

  Metaphyta, 161, 165.

  Metaplasm, 106, 129.

  Metaplasmosism, 107.

  Metasitism 217.

  Metazoa, 163.

  Micella, 137, 344.

  Micrococcus, 201, 202.

  Microgameton, 244.

  Middle Ages, thought in the, 66, 67.

  Mimicry, 421, 422.

  Mind, the, 315, 316;
    a function of the brain, 328-330;
    evolution of the, 319, 320, 322, 323, 326.

  Miracles, 60;
    in biology, 55;
    nature of, 54.

  Mohl, Hugo, 122.

  Molecular structure of the monera, 34, 137;
    theories of plasm, 342-346.

  Molecules, 126, 127.

  Monaxonia, 174.

  Monera, the, 31-33, 40, 157, 182, 190-209, 342.

  Monism, 81, 433-445.

  Monobia, 160, 196.

  Monoclinism, 247.

  Monœcia, 248.

  Monogamy, 240.

  Morality, 411, 412;
    a social instinct, 419, 420;
    conventional, 430;
    evolution of, 413, 414, 430-432;
    a form of adaptation, 414.

  Morphology, 94, 171.

  Morphonta, 149, 152.

  Motion in metabolism, 259.

  Müller, Johannes, on the nature of life, 49;
    on sensation, 288.

  Muscles, the, 273, 276-279;
    forms of in lower animals, 278;
    striated and non-striated, 277.

  Muscular cells, 277.

  Mutation theory, the, 365, 373.

  Myophæna, 269.


  Nägeli on evolution, 365;
    on plasm, 137;
    on the origin of life, 343, 344, 354, 356;
    on universality of sensation, 450.

  Natural history, 9.

  Naturalism, 86, 87.

  Necrobiosis, 106, 349.

  Neo-Darwinism, 375, 376.

  Neo-Lamarckism, 375, 376.

  Neovitalism, 48;
    sceptical and dogmatic, 50.

  Neurona, 12, 13, 328.

  Nitrobacteria, 201, 215, 218.

  Nuclein, 156.

  Nucleolus, 140.

  Nucleus of the cell, 122, 139, 155.

  Nutrition, progress in supply of, 401.


  Observation, subjective and objective, 7.

  Occultism, 74, 75.

  Œcology, 78, 95.

  Oken, Lorentz, 79, 80.

  Olfactory region, 303.

  Ontogeny, 94, 361, 376, 379.

  Optimism, 109, 110.

  Organella, 35, 130, 159, 163, 191.

  Organic chemistry, 37;
    and inorganic, differences between, 27, 28, 40;
    meaning of, 37;
    sensations, 302, 308.

  Organism, nature of an, 29, 30, 36.

  Organization, nature of, 29;
    progress of, 338;
    stages of, 149, 150, 151.

  Organs, 159, 163;
    apparatus of, 164;
    systems of, 164;
    of sense and thought, 12.

  Osmosis, 39.

  Ostwald, as a monist, 38;
    on enzyma, 46;
    on growth, 44;
    on mental energy, 330;
    system of, 85.

  Ovary, 325.

  Ovoplasm, 245.

  Ovulum, the, 245, 247, 250.


  Pædogenesis, 253.

  Palavitalism, 48, 49.

  Palingenesis, 382.

  Pangenesis theory, the, 366.

  Panpsychism, 340.

  Pantheism, 82.

  Paranuclein, 141.

  Parasites, 235-238.

  Parasitology, 235.

  Paratonic movement, 262, 274.

  Parthenogenesis, 251, 252.

  Passive movements in organisms, 262.

  Pasteur disproves spontaneous generation, 350-352.

  Paulospores, 244.

  Peptones, 45.

  Perception of stimuli, 292, 293, 296.

  Perigenesis of the plastidules, 136.

  Perpetual motion of universe, 258.

  Persons, 36, 148, 150, 154, 166, 183.

  Pessimism, 109, 110, 111.

  Pflüger on origin of life, 345, 346, 356.

  Philology, 461.

  Philosophy, history of, 81;
    modern, defects of, 453;
    nature of, 2, 3, 453, 454.

  Phoronomy, 259.

  Photo-synthesis, 214, 217.

  Phototaxis, 298.

  Phronema, the, 14, 15-17;
    structure of the, 329.

  Phroneta, the, 13, 329, 331.

  Phronetal cells, 14, 17.

  Phylogeny, 94, 361, 376, 379;
    sources of, 377.

  Physicians, liberal views of, 116-118.

  Physics, monism of, 455; nature of, 89, 454.

  Physiologists, dualism of, 18.

  Physiology, 93.

  Phytomonera, 193.

  Phytoplasm, 213, 217.

  Piano theory of the soul, 16.

  Pineal gland, the, 16.

  Planospores, 244.

  Plants, spontaneous movement in, 274, 275.

  Plasm, 121, 123, 128-146;
    chemical constituents of, 125, 126;
    differentiation of the, 138;
    molecules of, 136;
    nature of, 27, 28, 159;
    structure of, 128, 129, 130-138.

  Plasma products, 144.

  Plasmodomism, 33, 34, 130, 193, 197, 212, 213, 343, 357.

  Plasmogony, 354.

  Plasmophaga, 193, 196, 200, 212.

  Plasson, 158.

  Plassonella, 355, 358.

  Plastids, 138, 192.

  Plastidules, 136.

  Plastin, 141.

  Plate on Darwinism, 364.

  Platnosphæra, 174.

  Plato, dualism of, 436;
    philosophy of, 66.

  Platodes, 225.

  Pleuronectides, 178.

  Poetry, pedagogical value of, 439.

  Poisonous bacteria, 221, 305;
    fungi, 236.

  Polioplasm, 130, 143.

  Politics, 467.

  Polytomy, 243.

  Powder, 31.

  Pressure, sense of, 310.

  Preyer on the child-soul, 20;
    on the earth as an organism, 37;
    on universality of life, 340.

  Principle of individuation, 153.

  Probionta, 354.

  Promorphology, 94, 172.

  Protamœba, 206.

  Proteids, 126, 127.

  Protestants, liberalism among, 73.

  Protists, the, 34, 35, 131, 160, 171, 182, 190-209;
    can endure extreme temperatures, 300;
    movements of the, 267, 271;
    science of the, 92, 93;
    sensitiveness to electricity, 313.

  Protoplasm, 32;
    nature of, 121, 122, 125.

  Providence, belief in, 107, 108.

  Pseudopodia, 268.

  Psychiatry, 19, 329, 463.

  Psychogenesis, 21.

  Psychology, 461;
    comparative, 21, 22;
    modern, errors of, 71;
    monistic, 322;
    nature of, 18.

  Psycho-monism, 92.

  Psychophysics, 330.

  Pteridophyta, 162, 220.

  Ptomaines, 203.

  Purposive movement, 264, 265.

  Pyramidal types, 176.


  Radiolaria, 41, 156, 172, 181;
    movement in the, 322.

  Ranke, J., on evolution, 322.

  Rational sciences, 470.

  Reaction, 293.

  Realism, 90, 91.

  Reason, 316, 317;
    pure and practical, 317.

  Reason and authority, 423.

  Redemption, dogma of, 62.

  Reflex movement, 262, 263.

  Regeneration, organic, 101-105.

  Reinke, as vitalist, 51;
    dualism of, 30;
    on the monera, 31;
    on the origin of life, 337;
    theory of dominants, 264;
    works of, 80, 81.

  Release of energy, 294.

  Religion, evolution of, 57-65, 420, 421, 424.

  Reproduction a monistic process, 257;
    by division, 242;
    nature of, 241.

  Respiration, 228-232.

  Resurrection, the, 64.

  Resurrection plants, 262.

  Rhizomonera, 206.

  Rhizopods, 129, 192, 193, 219;
    movement in the, 270.

  Rhodocytes, 228.

  Rhumbler, L., on the cell-life, 132.

  Rhythmic beauty, 185.

  Richter, H. E., on life, 339.

  Rindfleisch, as vitalist, 51.

  Romanes, conversion of, 22, 23.

  Romanism, 63, 425, 426.


  Sacraments, 425, 426.

  Saposites, 234.

  Saprobiosis, 349, 350.

  Sarcode, 155.

  Savage, mind in the, 56, 57, 90, 333, 391, 405, 406, 424;
    religion of the, 57;
    sense-life in the, 406, 407;
    views of the, 390.

  Savages, higher, 394;
    life of the, 392-394;
    lower, 398;
    middle, 393.

  Schiller, idealism of, 439, 440-442.

  Schizpphyta, 201.

  Schleiden, 154.

  Schleiermacher, 72.

  Schopenhauer, as pessimist, 111, 112;
    on the categorical imperative, 412;
    on suicide, 114.

  Schultze, Max, on the cell, 155.

  Schwann, 154.

  Science, confusion in, 77;
    nature of, 4;
    schools of, 4;
    work of, 5, 6;
    value of, 407, 408.

  Science and tradition, conflict of, 70, 71.

  Secretory movement, 271.

  Selection, theory of, 361, 363.

  Self-cleavage, 242.

  Self-consciousness, beginning of, 323, 324.

  Semi-dogmatic sciences, 470.

  Senility, causes of, 106.

  Sensation and consciousness, 290, 291, 295.

  Sensation as attribute of substance, 447, 448;
    analysis of, 293;
    common to all bodies, 295, 296, 309;
    evolution of, 450;
    in atoms, 83;
    in plants, 292, 304;  nature of, 287-293;
    neglected by physiologists, 289, 292;
    of matter, 302;
    universal, 449.

  Sensations in savage and civilized man, 405, 406;
    organic, 302, 308.

  Sense-centres, 13, 329.

  Senses, finer development of the, 406.

  Sensibility, 287, 288, 293.

  Sensitiveness, 293.

  Sensorium, the, 14.

  Sensualism, 4, 14, 15.

  Sentiment and reason, 120.

  Sex sense, the, 245.

  Sexual beauty, 186.

  ---- characters, secondary, 251.

  ---- generation, 244-253.

  ---- selection, 251.

  ---- sense, the, 306, 307.

  Shame, feeling of, 423.

  Sight, evolution of, 24.

  Silicon, 40.

  Skeletal theory of plasm, 113.

  Skeleton, common type of the, 371.

  ---- the, 278, 279, 283, 284.

  Sleep of flowers, 274.

  Smell, 303, 304.

  Snails, evolution of the, 279;
    muscles of the, 278.

  Sociology, 467.

  Soul, the, 315, 324;
    dualistic idea of the, 15, 16;
    found in all substance, 397;
    seat of the, 15-18.

  Space, nature of, 70;
    sense of, 311.

  Spallanzani and spontaneous generation, 350.

  Spartan selection, 22, 119.

  Specialism, dangers of, 92.

  Species, nature of the, 204.

  Speech, 461.

  Sperm-plasm, 245.

  Spermatozoon, the, 245;
    movement of the, 271, 272.

  Spinoza, system of, 82;
    monism of, 445.

  Spirilla, 202.

  Spiritism, 74, 75,

  Spiritualism, 451.

  Spontaneous generation, 348;
    conflict over, 349, 350;
    older belief in, 349.

  Sporangia, 244.

  Spores, 244.

  Sporozoa, 235.

  Sprouts, 36, 148, 151, 154, 165, 183.

  State and the individual, the, 409.

  States, modern, defects of, 409, 410.

  Stationary life in animals, 275.

  Stauraxonia, 175.

  Stimuli, acoustic, 311;
    action of, 295;
    chemical, 301-309;
    conduction of, 295, 396;
    electric, 312, 313;
    gravitational, 309-312;
    optic, 297-300;
    thermic, 299-302.

  Stock, the, 168, 184.

  Strauss, D. F., 72.

  Strophogenesis, 254.

  Substance, attributes of, 446, 448;
    eternity, of, 97;
    the problem of, 2.

  Suicide, contradictory views of, 112;
    occasional justice of, 112, 113, 116.

  Sun-dew, action of the, 304.

  Supernatural, the, 87, 88.

  Superstition, 56.

  Sutherland, A., on morality, 392.

  Swimming-bladder, the, 231.

  Symbiosis, 238.

  Symmetry, 171, 172.

  Sympathy, 115.


  Tailor theory, the, 383.

  Tape-worms, 237.

  Taste, 302, 303.

  Technical science, progress of, 465.

  Tectology, 94.

  Teleology, 181, 366.

  Teleology in movement, 265.

  Teleology, mechanical, 362, 363.

  Temperature, perception of, 299-301.

  Thallophyta, 161, 165.

  Thallus, the, 165, 195.

  Theology, 468.

  Thermotaxis, 301.

  Thigmotaxis, 310.

  Thought as attribute of substance, 445.

  Thought centres, 13, 329.

  Time, nature of, 70.

  Tissue animals, 163;
    plants, 162.

  Tissues, primary and secondary, 161, 162.

  Tocogony, 240.

  Touch, sense of, 309;
    in plants, 300, 310.

  Tracheata, the, 231.

  Tradition, power of, 423.

  Transgressive growth, 42, 44, 240, 241.

  Transubstantiation, 426.

  Treviranus, 79.

  Tropesis, 296, 308.

  Trophoplasts, 143.

  Truth, nature of, 1, 2, 4.

  Tübingen school, the, 72.

  Turgescence movements, 274, 275.

  Turgor, 273-275.

  Types of organic structure, 173-184.


  Unequal value of life, 390.


  Value of modern life, 408, 409.

  Variability in species, 373.

  Variation movements, 274.

  Veddahs, the, 393.

  Vegetal diet, 227.

  Vertebrates, mind in the, 328;
    motor apparatus of the, 283, 284;
    succession of the, 327.

  Verworn, Max. on enzyma, 46;
    on the nature of life, 28;
    on the origin of life, 348.

  Vibratory movement, 271.

  Virchow and evolution, 322;
    on the aim of science, 5.

  Vital force, the, 47-51.

  ---- movement, 266-286.

  Vitalism, 47-51, 459.

  Voluntary movement mechanical, 262-264.


  War, 400, 409.

  Watch compared with organism, 30.

  Water-feet, 280.

  Water-vessels, 230.

  Weismann on immortality, 90-101;
    on selection, 364;
    on the structure of plasm, 137.

  Will, freedom of the, 263, 265, 286.

  Wind-pipe, the, 232.

  Woman, improvement in position of, 402.


  Zehnder on the origin of life, 344.

  Ziegler on instinct, 418.

  Zoomonera, 193, 219.

  Zooplasm, 213.


                                THE END




                              FOOTNOTES:

[1] The English translation met with almost equal success. Nearly
one hundred thousand copies of the cheap edition have already been
sold.--TRANS.

[2] Further particulars about the relations of the thought-centres to
the sense-centres will be found in the tenth chapter of _The Riddle of
the Universe_.

[3] English readers who are acquainted with Romanes's posthumous
_Thoughts on Religion_ will recognize the justice of this analysis.
Romanes speaks expressly of the acceptance of Christianity entailing
"the sacrifice of his intellect."--TRANS.

[4] This refers almost entirely to Germany. The reader will remember
that, when Lord Kelvin endeavored to make theosophic capital out
of this temporary confusion in German science, he was immediately
silenced by the leading biologists of this country, Professor E.
Ray-Lankester (for zoology), Sir W. T. Thiselton-Dyer (for botany),
and Sir J. Burdon-Sanderson (for physiology), who sharply rejected
vitalism.--TRANS.

[5] The German word _wunder_ corresponds equally to the English
"miracle" and "wonder." It has seemed necessary to translate it
"wonder" in the title of the work, but frequently as "miracle" in this
chapter.--TRANS.

[6] The English reader may usefully be reminded that Professor Loofs,
Haeckel's chief critic, and one of the foremost German theologians,
rejects these articles of the Creed no less than Haeckel does. A glance
at the pertinent articles in the _Encyclopædia Biblica_ will show how
widely theologians now discard these beliefs.--TRANS.

[7] Compare the opinion of the distinguished American psychologist,
Münsterberg "Science opposes to any doctrine of individual immortality
an unbroken and impregnable barrier" (_Psychology and Life_, p.
85).--TRANS.

[8] A translation of the latest edition of the _Anthropogenie_, with
the full number of fresh illustrations (thirty plates and five hundred
and twelve wood-cuts), will be issued very shortly by the Rationalist
Press Association, under the title of _The Evolution of Man_.

[9] I may remind the English reader that the chosen ecclesiastical
champion against Haeckel in this country, the Rev. F. Ballard, made
this extraordinary fallacy the very pith of his "scientific" attack on
monism.--TRANS.

[10] As already stated, it will presently appear in England with the
title, _The Evolution of Man_.--TRANS.

[11] At the moment I translate this, telegrams from Germany announce
that, by the emperor's orders, a number of ladies were excluded from
the opera for not observing this custom.--TRANS.

[12] The English reader will find in this a reply to the foolish notion
which has been circulated that the recent discovery of radioaction
and the composition of the atom from electrons has affected Haeckel's
position. His monism is completely indifferent to changes in the
physicist conception of the nature of matter.--TRANS.




                         TRANSCRIBER'S NOTES:

--Obvious print and punctuation errors were corrected.

--The large tables at pages 96 and 189 have been splitted into two parts.

--Original work has "CHAPTER I" instead of "CHAPTER VI" at page 121.
  Corrected.

--Original work does not have "XI" at the beginning of chapter (page 239).
  Added.