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The Fauna of British India, Including Ceylon and Burma.

Published Under the Authority of the Secretary of
State for India in Council.

Edited by A. E. Shipley, M.A., Sc.D., HON. D.Sc., F.R.S.


FRESHWATER SPONGES, HYDROIDS & POLYZOA.

by

N. ANNANDALE, D.SC.,

Superintendent and Trustee (_Ex Officio_) of the Indian Museum,
Fellow of the Asiatic Society of Bengal and of the Calcutta University.







London:
Taylor and Francis, Red Lion Court, Fleet Street.

Calcutta:
Thacker, Spink, & Co.

Bombay:
Thacker & Co., Limited.

Berlin:
R. Friedländer & Sohn, 11 Carlstrasse.

August, 1911.

Printed at Today & Tomorrow's Printers & Publishers, Faridabad




CONTENTS.

                                                                   Page

  EDITOR'S PREFACE                                                    v

  SYSTEMATIC INDEX                                                  vii

  GENERAL INTRODUCTION                                                1
    Biological Peculiarities                                          2
    Geographical Distribution                                         5
    Geographical List                                                 7
    Special Localities                                               13
    Nomenclature and Terminology                                     17
    Material                                                         20

  INTRODUCTION TO PART I. (_Spongillidæ_)                            27
    The Phylum Porifera                                              27
    General Structure                                                29
    Skeleton and Spicules                                            33
    Colour and Odour                                                 35
    External Form and Consistency                                    37
    Variation                                                        39
    Nutrition                                                        41
    Reproduction                                                     41
    Development                                                      45
    Habitat                                                          47
    Animals and Plants commonly associated with Freshwater Sponges   49
    Freshwater Sponges in relation to Man                            50
    Indian Spongillidæ compared with those of other Countries        51
    Fossil Spongillidæ                                               52
    Oriental Spongillidæ not yet found in India                      52
    History of the Study of Freshwater Sponges                       54
    Literature                                                       55

  GLOSSARY OF TECHNICAL TERMS USED IN PART I.                        61

  SYSTEMATIC LIST OF THE INDIAN SPONGILLIDÆ                          63

  INTRODUCTION TO PART II. (_Hydrida_)                              129
    The Phylum Coelenterata and the Class Hydrozoa                  129
    Structure of Hydra                                              130
    Capture and Ingestion of Prey: Digestion                        133
    Colour                                                          134
    Behaviour                                                       135
    Reproduction                                                    136
    Development of the Egg                                          139
    Enemies                                                         139
    Coelenterates of Brackish Water                                 139
    Freshwater Coelenterates other than Hydra                       141
    History of the Study of Hydra                                   142
    Bibliography of Hydra                                           143

  GLOSSARY OF TECHNICAL TERMS USED IN PART II.                      145

  LIST OF THE INDIAN HYDRIDA                                        146

  INTRODUCTION TO PART III. (_Ctenostomata_ and _Phylactolæmata_)   163
    Status and Structure of the Polyzoa                             163
    Capture and Digestion of Food: Elimination of Waste Products    166
    Reproduction: Budding                                           168
    Development                                                     170
    Movements                                                       172
    Distribution of the Freshwater Polyzoa                          173
    Polyzoa of Brackish Water                                       174
    History of the Study of Freshwater Polyzoa                      177
    Bibliography of the Freshwater Polyzoa                          178

  GLOSSARY OF TECHNICAL TERMS USED IN PART III.                     181

  SYNOPSIS OF THE CLASSIFICATION OF THE POLYZOA                     183

  SYNOPSIS OF THE SUBCLASSES, ORDERS, AND SUBORDERS                 183

  SYNOPSIS OF THE LEADING CHARACTERS OF THE DIVISIONS OF
    THE SUBORDER CTENOSTOMATA                                       185

  SYSTEMATIC LIST OF THE INDIAN FRESHWATER POLYZOA                  187

  APPENDIX TO THE VOLUME                                            239
    Hints on the Preparation of Specimens                           239

  ADDENDA                                                           242
    Part I.                                                         242
    Part II.                                                        245
    Part III.                                                       245

  ALPHABETICAL INDEX                                                249

  EXPLANATION OF PLATES.




EDITOR'S PREFACE.


Dr. N. Annandale's volume on the Freshwater SPONGES, POLYZOA, and
HYDRIDA contains an account of three of the chief groups of freshwater
organisms. Although he deals mainly with Indian forms the book contains
an unusually full account of the life-history and bionomics of
freshwater Sponges, Polyzoa, and Hydrozoa.

I have to thank Dr. Annandale for the great care he has taken in the
preparation of his manuscript for the press, and also the Trustees of
the Indian Museum, Calcutta, for their kindness in placing material at
the disposal of the Author.

                   A. E. SHIPLEY.
  Christ's College, Cambridge,
  March 1911.




  SYSTEMATIC INDEX.


                                            Page
  PORIFERA.

  Order HALICHONDRINA                         65

  Fam. 1. SPONGILLIDÆ                         65

  1. Spongilla, _Lamarck_                     67
    1A. Euspongilla, _Vejdovsky_              69
      1.     lacustris, _auct._               69
      1_a_.  reticulata, _Annandale_     71, 241
      2.     proliferens, _Annandale_         72
      3.     alba, _Carter_                   76
      3_a_.  cerebellata, _Bowerbank_         76
      3_b_.  bengalensis, _Annandale_         77
      4.     cinerea, _Carter_           79, 241
      5.     travancorica, _Annandale_        81
      6.     hemephydatia, _Annandale_        82
      7.     crateriformis (_Potts_)          83
    1B. Eunapius, _J. E. Gray_                86
      8.     carteri, _Carter_           87, 241
      8_a_.  mollis, _Annandale_              88
      8_b_.  cava, _Annandale_                88
      9.     fragilis, _Leidy_                95
      9_a_.  calcuttana, _Annandale_          96
      9_b_.  decipiens, _Weber_               97
     10.    gemina, _Annandale _              97
     11.    crassissima, _Annandale_          98
     11_a_. crassior, _Annandale_             98
    1C. Stratospongilla, _Annandale_         100
     12.    indica, _Annandale_              100
     13.    bombayensis, _Carter_       102, 241
     13_a_. pneumatica, _Annandale_          241
     14.    ultima, _Annandale_              104
  2. Pectispongilla, _Annandale_             106
     15.     aurea, _Annandale_              106
     15 _a_.  subspinosa, _Annandale_        107
  3. Ephydatia, _Lamouroux_                  108
     16.     meyeni (_Carter_)               108
             fluviatilis, _auct._            242
  4. Dosilia, _Gray_                         110
     17.     plumosa (_Carter_)              111
  5. Trochospongilla, _Vejdovsky_            113
     18.     latouchiana, _Annandale_        115
     19.     phillottiana, _Annandale_       117
     20.     pennsylvanica (_Potts_)         118
  6. Tubella, _Carter_                       120
     21.     vesparioides, _Annandale_       120
  7. Corvospongilla, _Annandale_             122
     22.     burmanica (_Kirkpatrick_)       123
             caunteri, _Annandale_           243
     23.     lapidosa (_Annandale_)          124

  HYDROZOA.

  Order ELEUTHEROBLASTEA                     147

  Fam. 1. HYDRIDÆ                            147

  1. Hydra, _Linné_                          147
     24.     vulgaris, _Pallas_              148
     25.     oligactis, _Pallas_        158, 245

  POLYZOA.

  Order CTENOSTOMATA                         189

  Div. 1.    Vesicularina                    189

  Fam. 1. VESICULARIDÆ                       189

  1. Bowerbankia, _Farre_                    189
         caudata, _Hincks_                   189
         bengalensis, _Annandale_            189

  Div. 2. Paludicellina                      190

  Fam. 1. PALUDICELLIDÆ                      191

  1. Paludicella, _Gervais_                  192
  2. Victorella, _Kent_                      194
     26.     bengalensis, _Annandale_        195

  Fam. 2. HISLOPIIDÆ                         199

  1. Hislopia, _Carter_                      199
     27.     lacustris, _Carter_             202
     27 _a_.  moniliformis, _Annandale_      204

  Order PHYLACTOLÆMATA                       206

  Div. 1. Plumatellina                       206

  Fam. 1. FREDERICELLIDÆ                     208

  1. Fredericella, _Gervais_                 208
     28.     indica, _Annandale_        210, 245

  Fam. 2. PLUMATELLIDÆ                       211

  Subfam. A. _Plumatellinæ_                  212

  1. Plumatella, _Lamarck_                   212
     29.     fruticosa, _Allman_             217
     30.     emarginata, _Allman_       220, 245
     31.     javanica, _Kraepelin_           221
     32.     diffusa, _Leidy_           223, 245
     33.     allmani, _Hancock_         224, 246
     34.     tanganyikæ, _Rousselet_    225, 246
     35.     punctata, _Hancock_             227
  2. Stolella, _Annandale_                   229
     36.     indica, _Annandale_             229
             himalayana, _Annandale_         246

  Subfam. B. _Lophopinæ_                     231

  1. Lophopodella, _Rousselet_               231
     37.     carteri (_Hyatt_)               232
     37 _a_.  himalayana (_Annandale_)       233
  2. Pectinatella, _Leidy_                   235
     38.     burmanica, _Annandale_          235




GENERAL INTRODUCTION TO THE VOLUME.


Although some zoologists have recently revived the old belief that the
sponges and the coelenterates are closely allied, no one in recent times
has suggested that there is any morphological relationship between
either of these groups and the polyzoa. Personally I do not think that
any one of the three groups is allied to any other so far as anatomy is
concerned; but for biological reasons it is convenient to describe the
freshwater representatives of the three groups in one volume of the
"Fauna."

Indeed, I originally proposed to the Editor that this volume should
include an account not only of the freshwater species, but of all those
that have been found in stagnant water of any kind. It is often
difficult to draw a line between the fauna of brackish ponds and marshes
and that of pure fresh water or that of the sea, and this is
particularly the case as regards the estuarine tracts of India and
Burma.

Pelseneer[A] has expressed the opinion that the Black Sea and the
South-east of Asia are the two districts in the world most favourable
for the study of the origin of a freshwater fauna from a marine one. The
transition in particular from the Bay of Bengal, which is much less salt
than most seas, to the lower reaches of the Ganges or the Brahmaputra is
peculiarly easy, and we find many molluscs and other animals of marine
origin in the waters of these rivers far above tidal influence.
Conditions are unfavourable in the rivers themselves for the development
and multiplication of organisms of many groups, chiefly because of the
enormous amount of silt held in suspension in the water and constantly
being deposited on the bottom, and a much richer fauna exists in ponds
and lakes in the neighbourhood of the rivers and estuaries than in
running water. I have only found three species of polyzoa and three of
sponges in running water in India, and of these six species, five have
also been found in ponds or lakes. I have, on the other hand, found
three coelenterates in an estuary, and all three species are essentially
marine forms, but two have established themselves in ponds of brackish
water, one (the sea-anemone _Sagartia schilleriana_) undergoing in so
doing modifications of a very peculiar and interesting nature. It is not
uncommon for animals that have established themselves in pools of
brackish water to be found occasionally in ponds of fresh water; but I
have not been able to discover a single instance of an estuarine species
that is found in the latter and not in the former.

     [Footnote A: "L'origine des animaux d'eau douce," Bull. de
     l'Acad. roy. de Belgique (Classe des Sciences), No. 12,
     1905, p. 724.]

For these reasons I intended, as I have said, to include in this volume
descriptions of all the coelenterates and polyzoa known to occur in
pools of brackish water in the estuary of the Ganges and elsewhere in
India, but as my manuscript grew I began to realize that this would be
impossible without including also an amount of general introductory
matter not justified either by the scope of the volume or by special
knowledge on the part of its author. I have, however, given in the
introduction to each part a list of the species found in stagnant
brackish water with a few notes and references to descriptions.


BIOLOGICAL PECULIARITIES OF THE SPONGES, COELENTERATES, AND POLYZOA OF
FRESH WATER.

There is often an external resemblance between the representatives of
the sponges, coelenterates, and polyzoa that causes them to be classed
together in popular phraseology as "zoophytes"; and this resemblance is
not merely a superficial one, for it is based on a similarity in habits
as well as of habitat, and is correlated with biological phenomena that
lie deeper than what are ordinarily called habits. These phenomena are
of peculiar interest with regard to difficult questions of nutrition and
reproduction that perhaps can only be solved by a close study of animals
living together in identical conditions and exhibiting, apparently in
consequence of so living, similar but by no means identical tendencies,
either anatomical or physiological, in certain directions.

One of the most important problems on which the study of the sponges,
coelenterates, and polyzoa of stagnant water throws light is that of the
production of resting buds and similar reproductive bodies adapted to
withstand unfavourable conditions in a quiescent state and to respond to
the renewal of favourable conditions by a renewed growth and activity.

Every autumn, in an English pond or lake, a crisis takes place in the
affairs of the less highly organized inhabitants, and preparations are
made to withstand the unfavourable conditions due directly or indirectly
to the low winter temperature of the water: the individual must perish
but the race may be preserved. At this season _Hydra_, which has been
reproducing its kind by means of buds throughout the summer, develops
eggs with a hard shell that will lie dormant in the mud until next
spring; the phylactolæmatous polyzoa produce statoblasts, the
ctenostomatous polyzoa resting-buds ("hibernacula"), and the sponges
gemmules. Statoblasts, hibernacula, and gemmules are alike produced
asexually, but they resemble the eggs of _Hydra_ in being provided with
a hard, resistant shell, and in having the capacity to lie dormant until
favourable conditions return.

In an Indian pond or lake a similar crisis takes place in the case of
most species, but it does not take place at the same time of year in the
case of all species. Unfortunately the phenomena of periodic
physiological change have been little studied in the freshwater fauna of
most parts of the country, and as yet we know very little indeed of the
biology of the Himalayan lakes and tarns, the conditions in which
resemble those to be found in similar masses of water in Europe much
more closely than they do those that occur in ponds and lakes in a
tropical plain. In Bengal, however, I have been able to devote
considerable attention to the subject, and can state definitely that
some species flourish chiefly in winter and enter the quiescent stage at
the beginning of the hot weather (that is to say about March), while
others reach their maximum development during the "rains" (July to
September) and as a rule die down during winter, which is the driest as
well as the coolest time of year.

The following is a list of the forms that in Bengal are definitely known
to produce hard-shelled eggs, gemmules, resting-buds, or statoblasts
only or most profusely at the approach of the hot weather and to
flourish during winter:--

     _Spongilla carteri._
     _Sponging alba._
     _Spongilla alba_ var. _bengalensis_.
     _Spongilla crassissima._
     _Hydra vulgaris._
     _Victorella bengalensis._
     _Plumatella fruticosa._
     _Plumatella emarginata._
     _Plumatella javanica._

The following forms flourish mainly during the "rains":--

     _Spongilla lacustris_ subsp. _reticulata_.
     _Trochospongilla latouchiana._
     _Trochospongilla phillottiana._
     _Stolella indica._

The following flourish throughout the year:--

     _Spongilla proliferens._
     _Hislopia lacustris._

It is particularly interesting to note that three of the species that
flourish in the mild winter of Bengal, namely _Hydra vulgaris_,
_Plumatella emarginata_, and _P. fruticosa_, are identical with species
that in Europe perish in winter. There is evidence, moreover, that the
statoblasts of the genus to which two of them belong burst more readily,
and thus give rise to new colonies, after being subjected to a
considerable amount of cold. In Bengal they only burst after being
subjected to the heat of the hot weather. Does extreme heat have a
similar effect on aquatic organisms as extreme cold? There is some
evidence that it has.

The species that flourish in India during the rains are all forms which
habitually live near the surface or the edge of ponds or puddles, and
are therefore liable to undergo desiccation as soon as the rains cease
and the cold weather supervenes.

The two species that flourish all the year round do not, properly
speaking, belong to one category, for whereas _Hislopia lacustris_
produces no form of resting reproductive body but bears eggs and
spermatozoa at all seasons, _Spongilla proliferens_ is a short-lived
organism that undergoes a biological crisis every few weeks; that is to
say, it begins to develop gemmules as soon as it is fully formed, and
apparently dies down as soon as the gemmules have attained maturity. The
gemmules apparently lie dormant for some little time, but incessant
reproduction is carried on by means of external buds, a very rare method
of reproduction among the freshwater sponges.

The facts just stated prove that considerable specific idiosyncrasy
exists as regards the biology of the sponges, hydroids, and polyzoa of
stagnant water in Bengal; but an even more striking instance of this
phenomenon is afforded by the sponges _Spongilla bombayensis_ and
_Corvospongilla lapidosa_ in Bombay. These two sponges resemble one
another considerably as regards their mode of growth, and are found
together on the lower surface of stones. In the month of November,
however, _C. lapidosa_ is in full vegetative vigour, while _C.
bombayensis_, in absolutely identical conditions, is already reduced to
a mass of gemmules, having flourished during the "rains." It is thus
clear that the effect of environment is not identical in different
species. This is more evident as regards the groups of animals under
consideration in India (and therefore probably in other tropical
countries) than it is in Europe. The subject is one well worthy of study
elsewhere than in India, for it is significant that specimens of _S.
bombayensis_ taken in November in S. Africa were in a state of activity,
thus contrasting strongly with specimens taken at the same time of year
(though not at the same season from a climatic point of view) in the
Bombay Presidency.


GEOGRAPHICAL DISTRIBUTION OF THE INDIAN SPECIES.

The geographical distribution of the lower invertebrates of fresh and of
stagnant water is often an extremely wide one, probably because the
individual of many species exists at certain seasons or in certain
circumstances in a form that is not only resistant to unfavourable
environment, but also eminently capable of being transported by wind or
currents. We therefore find that some genera and even species are
practically cosmopolitan in their range, while others, so far as our
knowledge goes, appear to have an extraordinarily discontinuous
distribution. The latter phenomenon may be due solely to our ignorance
of the occurrence of obscure genera or species in localities in which
they have not been properly sought for, or it may have some real
significance as indicating that certain forms cannot always increase and
multiply even in those localities that appear most suitable for them. As
an example of universally distributed species we may take the European
polyzoa of the genus _Plumatella_ that occur in India, while of species
whose range is apparently discontinuous better examples could not be
found than the sponges _Trochospongilla pennsylvanica_ and _Spongilla
crateriformis_, both of which are only known from N. America, the
British Isles, and India.

My geographical list of the species of sponges, coelenterates, and
polyzoa as yet found in fresh water in India is modelled on Col.
Alcock's recently published list of the freshwater crabs (Potamonidæ) of
the Indian Empire[B]. I follow him in accepting, with slight
modifications of my own, Blanford's physiographical rather than his
zoogeographical regions, not because I think that the latter have been
or ought to be superseded so far as the vertebrates are concerned, but
rather because the limits of the geographical distribution of aquatic
invertebrates appear to depend on different factors from those that
affect terrestrial animals or even aquatic vertebrates.

     [Footnote B: Cat. Ind. Dec. Crust. Coll. Ind. Mus., part i,
     fasc. ii (Potamonidæ), 1910.]

"Varieties" are ignored in this list, because they are not considered to
have a geographical significance. The parts of India that are least
known as regards the freshwater representatives of the groups under
consideration are the valley of the Indus, the lakes of Kashmir and
other parts of the Himalayas, the centre of the Peninsula, and the basin
of the Brahmaputra. Those that are best known are the districts round
Bombay, Calcutta, Madras and Bangalore, Travancore and Northern
Tenasserim. Little is known as regards Ceylon, and almost nothing as
regards the countries that surround the Indian Empire, a few species
only having been recorded from Yunnan and the Malay Peninsula, none from
Persia, Afghanistan, or Eastern Turkestan, and only one from Tibet.
Professor Max Weber's researches have, however, taught us something as
regards Sumatra and Java, while the results of various expeditions to
Tropical Africa are beginning to cast light on the lower invertebrates
of the great lakes in the centre of that continent and of the basin of
the Nile.

It is not known to what altitude the three groups range in the Himalayas
and the hills of Southern India. No sponge has been found in Indian
territory at an altitude higher than that of Bhim Tal in Kumaon (4,500
feet), and _Hydra_ is only known from the plains; but a variety of _H.
oligactis_ was taken by Capt. F. H. Stewart in Tibet at an altitude of
about 15,000 feet. _Plumatella diffusa_ flourishes at Gangtok in Sikhim
(6,100 feet), and I have found statoblasts of _P. fruticosa_ in the
neighbourhood of Simla on the surface of a pond situated at an altitude
of about 8,000 feet; Mr. R. Kirkpatrick obtained specimens of the genus
in the Botanical Gardens at Darjiling (6,900 feet), and two species have
been found at Kurseong (4,500-5,000 feet) in the same district.


GEOGRAPHICAL LIST OF THE FRESHWATER SPONGES, HYDROIDS, AND POLYZOA OF
INDIA, BURMA, AND CEYLON.

[A * indicates that a species or subspecies has only been found in one
physiographical region or subregion so far as the Indian Empire is
concerned; a ! that the species has also been found in Europe, a $ in
North America, a + in Africa, and a @ in the Malay Archipelago.]

1. Western Frontier Territory[C].

(Baluchistan, the Punjab, and the N.W. Frontier Province.)

     [Footnote C: I include Baluchistan in this territory largely
     for climatic reasons.]

  SPONGES:--
    1. _Spongilla_ (_Eunapius_) _carteri_!@ (Lahore).

  HYDROIDS:--
    1. _Hydra oligactis_!$ (Lahore).

  POLYZOA:--
    1. _Plumatella fruticosa_!$ (Lahore).
    2. _Plumatella diffusa_!$ (Lahore).


2. Western Himalayan Territory.

(Himalayas from Hazara eastwards as far as Nepal.)

  SPONGES:--
    1. _Spongilla_ (_Eunapius_) _carteri_!@ (Bhim Tal).
    2. _Ephydatia meyeni_@ (Bhim Tal).

  HYDROIDS:--None known (_Hydra oligactis_ recorded from Tibet).

  POLYZOA:--
    1. _Plumatella allmani_! (Bhim Tal).
    2. _Plumatella fruticosa_!$ (Simla).
    3. _Lophopodella carteri_+ (Bhim Tal).


3. North-Eastern Frontier Territory.

(Sikhim, Darjiling and Bhutan, and the Lower Brahmaputra
Drainage-System.)

  SPONGES:--
    _Spongilla proliferens_@ (Assam).

  HYDROIDS:--None known.

  POLYZOA:--
    1. _Plumatella fruticosa_! (Kurseong and Assam).
    2. _Plumatella diffusa_!$ (Sikhim).
    3. _Plumatella javanica_@ (Kurseong).


4. Burma Territory.

(Upper Burma, Arrakan, Pegu, Tenasserim.)

  SPONGES:--
    1. _Spongilla_ (_Euspongilla_) _proliferens_@ (Upper Burma, Pegu).
    2. _Spongilla_ (_Euspongilla_) _crateriformis_!$ (Tenasserim).
    3. _Spongilla_ (_Eunapius_) _carteri_!@ (Upper Burma, Pegu,
         Tenasserim).
    4. _Trochospongilla latouchiana_ (Tenasserim).
    5. _Trochospongilla phillottiana_ (Tenasserim).
    6. _Tubella vesparioides_* (Tenasserim).
    7. _Corvospongilla  burmanica_* (Pegu).

  HYDROIDS:--
    1. _Hydra vulgaris_!$ (Upper Burma and Tenasserim).

  POLYZOA:--
    1. _Plumatella emarginata_!$ (Pegu, Upper Burma).
    2. _Plumatella allmani_! (Tenasserim).
    3. _Pectinatella burmanica_ (Tenasserim).
    4. _Hislopia lacustris_ (Pegu).


5 _a._ Peninsular Province--Main Area.

(The Peninsula east of the Western Ghats.)

  SPONGES:--
    1. _Spongilla_ (_Euspongilla_) _lacustris_ subsp. _reticulata_
         (Orissa, Madras).
    2. _Spongilla_ (_Euspongilla_) _proliferens_@ (Madras).
    3. _Spongilla_ (_Euspongilla_) _alba_+ (N. Madras, Orissa, Hyderabad).
    4. _Spongilla_ (_Euspongilla_) _hemephydatia_* (Orissa).
    5. _Spongilla_ (_Euspongilla_) _crateriformis_!$.
    6. _Spongilla_ (_Eunapius_) _carteri_!@.
    7. _Spongilla_ (_Eunapius_) _gemina_* (Bangalore).
    8. _Spongilla_ (_Stratospongilla_) _bombayensis_+ (Mysore).
    9. _Dosilia plumosa_ (N. Madras).

  HYDROIDS:--
    1. _Hydra vulgaris_!$.

  POLYZOA:--
    1. _Plumatella fruticosa_! (Madras, Bangalore).
    2. _Lophopus_ (?_Lophopodella_), sp. (Madras).
    3. _Pectinatella burmanica_ (Orissa).
    4. _Victorella bengalensis_ (Madras).
    5. _Hislopia lacustris_ (Nagpur).


5b. Peninsular Province--Malabar Zone.

(Western Ghats from Tapti R. to Cape Comorin and eastwards
to the sea.)

  SPONGES:--
    1. _Spongilla_ (_Euspongilla_) _lacustris_ subsp. _reticulata_
         (W. Ghats).
    2. _Spongilla_ (_Euspongilla_) _proliferens_@ (Cochin).
    3. _Spongilla_ (_Euspongilla_) _alba_+.
    4. _Spongilla_ (_Euspongilla_) _cinerea_*.
    5. _Spongilla_ (_Euspongilla_) _travancorica_* (Travancore).
    6. _Spongilla_ (_Euspongilla_) _crateriformis_!$ (Cochin).
    7. _Spongilla_ (_Eunapius_) _carteri_!@.
    8. _Spongilla_ (_Stratospongilla_) _indica_* (W. Ghats).
    9. _Spongilla _ (_Stratospongilla_) _bombayensis_+ (Bombay, W. Ghats).
   10. _Spongilla_ (_Stratospongilla_) _ultima_* (Travancore).
   11. _Pectispongilla aurea_* (Travancore, Cochin).
   12. _Ephydatia meyeni_@ (Bombay, Travancore).
   13. _Dosilia plumosa_ (Bombay).
   14. _Trochospongilla pennsylvanica_*!$ (Travancore).
   15. _Corvospongilla lapidosa_* (W. Ghats).

  HYDROIDS:--None recorded.

  POLYZOA:--
    1. _Fredericella indica_* (W. Ghats and Travancore).
    2. _Plumatella fruticosa_! (Bombay).
    3. _Plumatella javanica_@ (Travancore).
    4. _Plumatella tanganyikæ_*+ (W. Ghats).
    5. _Lophopodella carteri_+ (Bombay, W. Ghats).


6. Indo-Gangetic Plain.

(From Sind to the Brahmaputra.)

  SPONGES:--
    1. _Spongilla_ (_Euspongilla_) _lacustris_ subsp. _reticulata_
         (Gangetic delta).
    2. _Spongilla_ (_Euspongilla_) _proliferens_@ (Lower Bengal, etc.).
    3. _Spongilla_ (_Euspongilla_) _alba_+ (Lower Bengal).
    4. _Spongilla_ (_Euspongilla_) _crateriformis_!$.
    5. _Spongilla_ (_Eunapius_) _carteri_!@ (Lower Bengal, etc.).
    6. _Spongilla_ (_Eunapius_) _fragilis_ subsp. _calcuttana_* (Lower
         Bengal).
    7. _Spongilla_ (_Eunapius_) _crassissima_ (Bengal).
    8. _Ephydatia meyeni_@ (Lower Bengal).
    9. _Trochospongilla latouchiana_ (Lower Bengal).
   10. _Trochospongilla phillottiana_ (Lower Bengal).

  HYDROIDS:--
    1. _Hydra vulgaris_!$.

  POLYZOA:--
    1. _Plumatella fruticosa_!.
    2. _Plumatella emarginata_!$.
    3. _Plumatella javanica_@ (Lower Bengal).
    4. _Plumatella diffusa_!$.
    5. _Plumatella allmani_!.
    6. _Plumatella punctata_!$ (Lower Bengal).
    7. _Stolella indica_* (Lower Bengal, United Provinces).
    8. _Victorella bengalensis_ (Lower Bengal).
    9. _Hislopia lacustris_ (United Provinces, N. Bengal).
    9a. _Hislopia lacustris_ subsp. _moniliformis_* (Lower Bengal).


7. Ceylon.

  SPONGES:--
    1. _Spongilla_ (_Euspongilla_) _proliferens_@.
    2. _Spongilla_ (_Eunapius_) _carteri_!@.

  HYDROIDS:--
    1. _Hydra vulgaris_!$.

  POLYZOA:--
    1. ? _Plumatella emarginata_!$.
    2. _Pectinatella burmanica._

The most striking feature of this list is the evidence it affords as to
the distinct character of the fauna of the Malabar Zone, a feature that
is also remarkably clear as regards the Potamonidæ, one genus of which
(_Gecarcinucus_) is peculiar, so far as India is concerned, to that
zone. As regards the sponges we may note the occurrence of no less than
three species of the subgenus _Stratospongilla_, which has not been
found elsewhere in India except on one occasion in Mysore, and of a
species of the genus _Corvospongilla_, which is unknown from the rest of
Peninsular India and from the Himalayas. The genus _Pectispongilla_ is
only known from the Malabar Zone. Among the polyzoa the genus
_Fredericella_[D] appears to be confined, so far as the Indian and
Burmese fauna is concerned, to the Malabar Zone, and the same is true as
regards the group of species to which _Plumatella tanganyikæ_, an
African form, belongs.

     [Footnote D: Mr. S. W. Kemp recently obtained at Mangaldai,
     near the Bhutan frontier of Assam, a single specimen of what
     may be a species of _Fredericella_.]

A further examination of the list of Malabar species and a consideration
of allied forms shows that the majority of the forms restricted to the
Malabar Zone are either African or else closely allied to African forms.
The genus _Corvospongilla_, except for one Burmese species, is otherwise
peculiar to Tropical Africa; while _Stratospongilla_, although not
confined to Africa, is more prolific in species in that continent than
in any other. _Spongilla (Stratospongilla) bombayensis_ has only been
found in Bombay, the Western Ghats, Mysore, and Natal, and _Plumatella
tanganyikæ_ only in the Western Ghats and Central Africa. The genus
_Fredericella_ (which also occurs in Europe, N. America, and Australia)
is apparently of wide distribution in Africa, while _Lophopodella_
(which in India is not confined to the Malabar Zone) is, except for a
Japanese race of the Indian species, restricted outside India, so far as
we know, to East Africa.

A less definite relationship between the sponges and polyzoa of the
Malabar Zone and those of countries to the east of India is suggested by
the following facts:--

     (1) The occurrence of the genus _Corvospongilla_ in Burma;

     (2) the occurrence of the subgenus _Stratospongilla_ in
     Sumatra, China, and the Philippines;

     (3) the occurrence of a race of _Lophopodella carteri_ in
     Japan;

     (4) the occurrence of a species allied to _Plumatella
     tanganyikæ_ in the Philippines.

It will be noted that in each of these instances the relationship
extends to Africa as well as to the Eastern countries, and is more
marked in the former direction. The species of _Stratospongilla_,
moreover, that occurs in Sumatra (_S. sumatrensis_) also occurs in
Africa, while those that have been found in China and the Philippines
are aberrant forms.

At first sight it might appear that these extra-Indian relationships
might be explained by supposing that gemmules and statoblasts were
brought to the Malabar Coast from Africa by the aërial currents of the
monsoon or by marine currents and carried from India eastwards by the
same agency, this agency being insufficient to transport them to the
interior and the eastern parts of the Peninsula. The work of La
Touche[E] on wind-borne foraminifera in Rajputana is very suggestive in
this direction; but that the peculiar sponge and polyzoon fauna of
Malabar is due to the agency either of wind or of marine currents may be
denied with confidence, for it is a striking fact that most of the
characteristic genera and subgenera of the Zone have resting
reproductive bodies that are either fixed to solid objects or else are
devoid of special apparatus to render them light. The former is the case
as regards all species of _Corvospongilla_ and all Indian and most other
species of _Stratospongilla_, the gemmules of which not only are
unusually heavy but also adhere firmly; while the statoblasts of
_Fredericella_ have no trace of the air-cells that render the free
statoblasts of all other genera of phylactolæmatous polyzoa peculiarly
light and therefore peculiarly liable to be transported by wind.

     [Footnote E: See Mem. Geol. Surv. Ind. XXXV (1), p. 39
     (1902).]

A true geographical or geological explanation must therefore be sought
for the relationship between the sponges and polyzoa of Malabar, of
Africa, and of the Eastern countries--a relationship that is well known
to exist as regards other groups of animals. No more satisfactory
explanation has as yet been put forward than that of a former land
connection between Africa and the Malaysia through Malabar at a period
(probably late Cretaceous) when the Western Ghats were much higher than
they now are[F].

     [Footnote F: See Ortmann, "The Geographical Distribution of
     Freshwater Decapods and its bearing upon Ancient Geography,"
     Proc. Amer. Phil. Soc. xli, p. 380, fig. 6 (1902); also
     Suess, "The Face of the Earth" (English ed.) i, p. 416
     (1904).]

There is little to be said as regards the distribution of the sponges,
hydroids, and polyzoa of fresh water in other parts of India. It may be
noted, however, that the species known from the Punjab are all widely
distributed Palæarctic forms, and that the genus _Stolella_ is
apparently confined to the Indo-Gangetic Plain. Two species of sponge
are peculiar to Lower Burma, one of them (_Corvospongilla burmanica_)
representing the geographical alliance already discussed as regards the
Malabar Zone, the other (_Tubella vesparioides_) closely related to a
Malaysian species (_T. vesparium_ from Borneo) and perhaps representing
the northern limit of the Malaysian element well known in the fauna of
Lower Burma. Of the sponges and polyzoa of Ceylon we know as yet too
little to make it profitable to discuss their affinities. All that have
as yet been discovered occur also in Peninsular India; nor do they
afford any evidence of a connection with the Malabar Zone.

The question of the geographical range of the sponges, hydroids, and
polyzoa of brackish water may be considered briefly, for it is of
importance in considering that of those which are confined to fresh
water. Some of these species from brackish water (e. g., _Membranipora
lacroixii_) are identical with others (e. g., _Victorella bengalensis_
and _Bowerbankia caudata_ subsp. _bengalensis_) closely related to
European forms. Others again (e. g., _Loxosomatoides colonialis_ and
_Sagartia schilleriana_) are known as yet from the Ganges delta only. In
our ignorance of the Indian representatives of the groups to which they
belong, it is impossible to assert that their distribution is actually
so restricted as it seems.


SOME SPECIAL LOCALITIES.

In order to avoid constant repetition as regards the conditions that
prevail at the places most frequently mentioned in this volume, a few
details as regards them may be conveniently stated here.

_Lower Bengal._

CALCUTTA is situated on the River Hughli at a point about 90 miles from
the open sea. The water of the river is practically fresh, but is
strongly affected by the tides; it is always turbid and of a brownish
colour. The river, however, is not a good collecting ground for sponges,
coelenterates, and polyzoa, and none of the species described in this
volume have been obtained from it. It is in the Calcutta "tanks" that
most of my investigations have been made. These tanks are ponds, mostly
of artificial origin, very numerous, of varying size but never very
large or deep. Most of them contain few solid objects to which sedentary
organisms can fix themselves, and such ponds are of course poor in
sponges and polyzoa. Others, however, support a prolific growth of weeds
such as _Pistia stratiotes_, _Lemna_, and _Limnanthemum_, and a few have
brickwork or artificial stonework at their sides. In those parts of the
town that approach the Salt Lakes (large lagoons and swamps of brackish
water connected with the sea by the Mutlah River) the water of the ponds
is slightly brackish and permits few plants except algæ to flourish. Few
of the bigger tanks ever dry up. The best of the tanks from the
sponge-collector's point of view, so far as I have been able to
discover, is the one in the compound of the Indian Museum. It enjoys all
the advantages of light and shade, solid supports, prolific aquatic
vegetation, considerable depth, and the vicinity of human dwellings that
seem to be favourable to the growth of sponges, no less than nine
species of which, representing three genera and two subgenera, grow
abundantly in it. _Hydra_ also flourishes in this pond, but for some
reasons there are few polyzoa. The phylactolæmatous species of the
latter group, however, are extraordinarily abundant in one of the tanks
in the Zoological Gardens at Alipore. In this tank, which unlike the
Museum tank is directly connected with the river, no less than six
species and varieties of the genus _Plumatella_ have been found growing
together on sticks, floating seeds, and water-plants. Except _Hislopia_,
which is common on _Vallisneria_ in one tank on the Maidan (opposite the
Bengal Club), the ctenostomes of stagnant water are only found in the
tanks near the Salt Lakes.

PORT CANNING is situated on the Mutlah River about 30 miles from
Calcutta and about 60 from the open sea. The Mutlah is really a tidal
creek rather than a river, in spite of the fact that it runs for a
considerable number of miles, and its waters are distinctly brackish.
Water taken from the edge at Port Canning in March was found to contain
25.46 per thousand of saline residue. The interesting feature of Port
Canning, however, is from a zoological point of view not the Mutlah but
certain ponds of brackish water now completely separated from it, except
occasionally when the river is in flood, but communicating regularly
with it in the memory of living persons. These ponds, which were
apparently not in existence in 1855, have on an average an area of about
half an acre each, and were evidently formed by the excavation of earth
for the construction of an embankment along the Mutlah. They are very
shallow and lie exposed to the sun. The salinity differs considerably in
different ponds, although the fauna seems to be identical; the water of
one pond was found to contain 22.88 per thousand of saline residue in
May, 20.22 per thousand in March, and 12.13 in December. A second pond
in the neighbourhood of the first and apparently similar to it in every
way contained only 9.82 per thousand in July, after the rains had
broken. The fauna of these ponds includes not only a freshwater sponge
(_Spongilla alba_ var. _bengalensis_) but also many aquatic insects
(_e. g._, larvæ of mosquitos and of _Chironomus_ and several species of
beetles and Rhynchota); while on the other hand essentially marine
coelenterates (_Irene ceylonensis_, etc.) and worms (_e. g._, the
gephyrean _Physcosoma lurco_[G]) form a part of it, together with forms
of intermediate habitat such as _Bowerbankia caudata_ subsp.
_bengalensis_, _Victorella bengalensis_, and several fish and crustacea
common in brackish water.

     [Footnote G: I am indebted to Mr. W. F. Lanchester for the
     identification of this species.]

_Orissa._

Orissa may be described in general terms as consisting of the coastal
area of Bengal south of the Gangetic delta. It extends in inland,
however, for a considerable distance and includes hilly tracts. There is
no geographical boundary between it and the north-eastern part of the
Madras Presidency or the eastern part of the Central Provinces.

CHILKA LAKE.--This marine lake is a shallow lagoon measuring about 40
miles in length and 10 miles in breadth, and formed in geologically
recent times by the growth of a narrow sand-bank across the mouth of a
wide bay. At its northern end it communicates with the sea by a narrow
channel, and throughout its length it is strongly affected by the tides.
At its south end, which is actually situated in the Ganjam district of
Madras, the water is distinctly brackish and is said to be nearly fresh
at certain times of year. At this end there are numerous small
artificial pools of brackish water somewhat resembling those of Port
Canning as regards their fauna.

SUR (or SAR) LAKE.--A shallow, freshwater lake of very variable size
situated a few miles north of Puri on the Orissa coast. In origin it
probably resembled the Chilka Lake, but it is now separated from the sea
by about 3 miles of barren sand dunes, among which numerous little pools
of rain-water are formed during the rains. These dry up completely in
winter, and even the lake itself is said sometimes almost to disappear,
although when it is full it is several miles in length. The fauna is
essentially a freshwater one, but includes certain Mysidæ and other
crustacea usually found in brackish water.

_Bombay Presidency._

BOMBAY.--The town of Bombay, built on an island near the mainland, is
situated close to swamps and creeks of brackish water not unlike those
that surround Calcutta. Its "tanks," however, differ from those of
Calcutta in having rocky bottoms and, in many cases, in drying up
completely in the hot weather. Of the fauna of the swamps extremely
little is known, but so far as the sponges and polyzoa of the tanks are
concerned the work undertaken by Carter was probably exhaustive.

IGATPURI.--Igatpuri is situated at an altitude of about 2000 feet, 60
miles north-east of Bombay. Above the town there is a lake of several
square miles in area whence the water-supply of several stations in the
neighbourhood is obtained. The water is therefore kept free from
contamination. The bottom is composed of small stones and slopes
gradually up at the edges. During the dry weather its level sinks
considerably. Several interesting sponges and polyzoa have been found in
this lake, most of them also occurring in a small pond in the
neighbourhood in which clothes are washed and the water is often full of
soap-suds.

_Southern India._

MADRAS.--The city of Madras is built by the sea, straggling over a large
area of the sandy soil characteristic of the greater part of the east
coast of India. In wet weather this soil retains many temporary pools of
rain-water, and there are numerous permanent tanks of no great size in
the neighbourhood of the town. The so-called Cooum River, which flows
through the town, is little more than a tidal creek, resembling the
Mutlah River of Lower Bengal on a much smaller scale. The sponges and
polyzoa as yet found in the environs of Madras are identical with those
found in the environs of Calcutta.

BANGALORE.--Bangalore (Mysore State) is situated near the centre of the
Madras Presidency on a plateau about 3000 feet above sea-level. The
surrounding country is formed of laterite rock which decomposes readily
and forms a fine reddish silt in the tanks. These tanks are numerous,
often of large size, and as a rule at least partly of artificial origin.
Their water supports few phanerogamic plants and is, as my friend Dr.
Morris Travers informs me, remarkably free from salts in solution. The
sponge fauna of the neighbourhood of Bangalore appears to be
intermediate between that of Madras and that of Travancore.

THE BACKWATERS OF COCHIN AND TRAVANCORE.--The "backwaters" of Cochin and
Travancore were originally a series of shallow lagoons stretching along
the coast of the southern part of the west coast of India for a distance
of considerably over a hundred miles. They have now been joined together
by means of canals and tunnels to form a tidal waterway, which
communicates at many points directly with the sea. The salinity of the
water differs greatly at different places and in different seasons, and
at some places there is an arrangement to keep out sea-water while the
rice-fields are being irrigated. The fauna is mainly marine, but in the
less saline parts of the canals and lakes many freshwater species are
found.

_Shasthancottah._--There are two villages of this name, one situated on
the backwater near Quilon (coast of Travancore), the other about three
miles inland on a large freshwater lake. This lake, which does not
communicate with the backwater, occupies a narrow winding rift several
miles in length at a considerable depth below the surrounding country.
Its bottom is muddy and it contains few water-plants, although in some
places the water-plants that do exist are matted together to form
floating islands on which trees and bushes grow. The fauna, at any rate
as regards mollusca and microscopic organisms, is remarkably poor, but
two species of polyzoa (_Fredericella indica_ and _Plumatella
fruticosa_) and one of sponge (_Trochospongilla pennsylvanica_) grow in
considerable abundance although not in great luxuriance.

_The Himalayas._

BHIM TAL[H] is a lake situated at an altitude of 4500 feet in that part
of the Western Himalayas known as Kumaon, near the plains. It has a
superficial area of several square miles, and is deep in the middle. Its
bottom and banks are for the most part muddy. Little is known of its
fauna, but two polyzoa (_Plumatella allmani_ and _Lophopodella carteri_)
and the gemmules of two sponges (_Spongilla carteri_ and _Ephydatia
meyeni_) have been found in it.

     [Footnote H: The fauna of this lake and of others in the
     neighbourhood has recently been investigated by Mr. S. W.
     Kemp. See the addenda at the end of this volume.--_June
     1911._]

       *     *     *     *     *

NOMENCLATURE AND TERMINOLOGY.

The subject of nomenclature may be considered under four heads:--(I.)
the general terminology of the various kinds of groups of individuals
into which organisms must be divided; (II.) the general nomenclature of
specimens belonging to particular categories, such as types, co-types,
etc.; (III.) the nomenclature that depends on such questions as that of
"priority"; and (IV.) the special terminology peculiar to the different
groups. The special terminology peculiar to the different groups is
dealt with in the separate introductions to each of the three parts of
this volume.


(I.)

No group of animals offers greater difficulty than the sponges,
hydroids, and polyzoa (and especially the freshwater representatives of
these three groups) as regards the question "What is a species?" and the
kindred questions, "What is a subspecies?" "What is a variety?" and
"What is a phase?" Genera can often be left to look after themselves,
but the specific and kindred questions are answered in so many different
ways, if they are even considered, by different systematists, especially
as regards the groups described in this volume, that I feel it necessary
to state concisely my own answers to these questions, not for the
guidance of other zoologists but merely to render intelligible the
system of classification here adopted. The following definitions should
therefore be considered in estimating the value of "species," etc.,
referred to in the following pages.

_Species._--A group of individuals differing in constant characters of a
definite nature and of systematic[I] importance from all others in the
same genus.

     [Footnote I: "What characters are of systematic importance?"
     is a question to which different answers must be given in
     the case of different groups.]

_Subspecies._--An isolated or local race, the individuals of which
differ from others included in the same species in characters that are
constant but either somewhat indefinite or else of little systematic
importance.

_Variety._--A group of individuals not isolated geographically from
others of the same species but nevertheless exhibiting slight, not
altogether constant, or indefinite differences from the typical form of
the species (_i. e._, the form first described).

_Phase._--A peculiar form assumed by the individuals of a species which
are exposed to peculiarities in environment and differ from normal
individuals as a direct result.

There are cases in which imperfection of information renders it
difficult or impossible to distinguish between a variety and a
subspecies. In such cases it is best to call the form a variety, for
this term does not imply any special knowledge as regards its
distribution or the conditions in which it is found.

I use the term "form" in a general sense of which the meaning or
meanings are clear without explanation.


(II.)

The question of type specimens must be considered briefly. There are two
schools of systematists, those who assert that one specimen and one only
must be the type of a species, and those who are willing to accept
several specimens as types. From the theoretical point of view it seems
impossible to set up any one individual as the ideal type of a species,
but those who possess collections or are in charge of museums prefer,
with the natural instinct of the collector, to have a definite single
type (of which no one else can possibly possess a duplicate) in their
possession or care, and there is always the difficulty that a zoologist
in describing a species, if he recognizes more than one type, may
include as types specimens that really belong to more than one species.
These difficulties are met by some zoologists by the recognition of
several specimens as paratypes, all of equal value; but this, after all,
is merely a terminological means of escaping from the difficulty,
calculated to salve the conscience of a collector who feels unwilling to
give up the unique type of a species represented by other specimens in
his collection. The difficulty as regards the confounding of specimens
of two or more species as the types of one can always be adjusted if the
author who discovers the mistake redescribes one of the species under
the original name and regards the specimen that agrees with his
description as the type, at the same time describing a new species with
another of the specimens as its type. Personally I always desire to
regard the whole material that forms the basis of an original
description of a species as the type, but museum rules often render this
impossible, and the best that can be done is to pick out one specimen
that seems particularly characteristic and to call it the type, the rest
of the material being termed co-types. A peculiar difficulty arises,
however, as regards many of the sponges, coelenterates, and polyzoa,
owing to the fact that they are often either compound animals, each
specimen consisting of more than one individual, or are easily divisible
into equivalent fragments. If the single type theory were driven to its
logical conclusion, it would be necessary to select one particular polyp
in a hydroid colony, or even the part of a sponge that surrounded a
particular osculum as the type of the species to which the hydroid or
the sponge belonged. Either by accident or by design specimens of
Spongillidæ, especially if kept dry, are usually broken into several
pieces. There is, as a matter of fact, no reason to attribute the
peculiarly sacrosanct nature of a type to one piece more than another.
In such cases the biggest piece may be called the type, while the
smaller pieces may be designated by the term "schizotype."

The more precise definition of such terms as topotype, genotype, _et
hujus generis omnis_ is nowadays a science (or at any rate a form of
technical industry) by itself and need not be discussed here.


(III.)

In 1908 an influential committee of British zoologists drew up a
strenuous protest against the unearthing of obsolete zoological names
(see 'Nature,' Aug. 1908, p. 395). To no group does this protest apply
with greater force than to the three discussed in this volume. It is
difficult, however, to adopt any one work as a standard of nomenclature
for the whole of any one of them. As regards the Spongillidæ it is
impossible to accept any monograph earlier than Potts's "Fresh-Water
Sponges" (P. Ac. Philad., 1887), for Bowerbank's and Carter's earlier
monographs contained descriptions of comparatively few species. Even
Potts's monograph I have been unable to follow without divergence, for
it seems to me necessary to recognize several genera and subgenera that
he ignored. The freshwater polyzoa, however, were dealt with in so
comprehensive a manner by Allman in his "Fresh-Water Polyzoa" (London,
1856) that no difficulty is experienced in ignoring, so far as
nomenclature is concerned, any earlier work on the group; while as
regards other divisions of the polyzoa I have followed Hincks's "British
Marine Polyzoa" (1880), so far as recent researches permit. In most
cases I have not attempted to work out an elaborate synonymy of species
described earlier than the publication of the works just cited, for to
do so is a mere waste of time in the case of animals that call for a
most precise definition of species and genera and yet were often
described, so far as they were known earlier than the dates in question,
in quite general terms. I have been confirmed in adopting this course by
the fact that few of the types of the earlier species are now in
existence, and that a large proportion of the Indian forms have only
been described within the last few years.


MATERIAL.

The descriptions in this volume are based on specimens in the collection
of the Indian Museum, the Trustees of which, by the liberal manner in
which they have permitted me to travel in India and Burma on behalf of
the Museum, have made it possible not only to obtain material for study
and exchange but also to observe the different species in their natural
environment. This does not mean to say that specimens from other
collections have been ignored, for many institutions and individuals
have met us generously in the matter of gifts and exchanges, and our
collection now includes specimens of all the Indian forms, named in
nearly all cases by the author of the species, except in those of
species described long ago of which no authentic original specimens can
now be traced. Pieces of the types of all of the Indian Spongillidæ
described by Carter have been obtained from the British Museum through
the kind offices of Mr. R. Kirkpatrick. The Smithsonian Institution has
sent us from the collection of the United States National Museum
specimens named by Potts, and the Berlin Museum specimens named by
Weltner, while to the Imperial Academy of Sciences of St. Petersburg we
owe many unnamed but interesting sponges. Dr. K. Kraepelin and Dr. W.
Michaelsen have presented us with specimens of most of the species and
varieties of freshwater polyzoa described by the former in his great
monograph and elsewhere. We owe to Dr. S. F. Harmer, formerly of the
Cambridge University Museum and now Keeper in Zoology at the British
Museum, to Professor Max Weber of Amsterdam, Professor Oka of Tokyo, and
several other zoologists much valuable material. I would specially
mention the exquisite preparations presented by Mr. C. Rousselet.
Several naturalists in India have also done good service to the Museum
by presenting specimens of the three groups described in this volume,
especially Major H. J. Walton, I.M.S., Major J. Stephenson, I.M.S., Dr.
J. R. Henderson and Mr. G. Matthai of Madras, and Mr. R. Shunkara
Narayana Pillay of Trivandrum.

The following list shows where the types of the various species,
subspecies, and varieties are preserved, so far as it has been possible
to trace them. I have included in this list the names of all species
that have been found in stagnant water, whether fresh or brackish, but
those of species not yet found in fresh water are enclosed in square
brackets.

+-----------------------------------------------------------------------+
|                       INDIAN SPONGILLIDÆ.                             |
|                                                                       |
+---------------------------------+----------------------+--------------+
|         NAME.                   |   TYPE IN COLL.      |  MATERIAL    |
|                                 |                      |  EXAMINED.   |
+---------------------------------+----------------------+--------------+
| _Spongilla lacustris_ subsp.    | Ind. Mus.            |    Type.     |
| _reticulata_                    |                      |              |
+---------------------------------+----------------------+--------------+
| _Spongilla proliferens_         |   "   "              |       "      |
+---------------------------------+----------------------+--------------+
| _Spongilla alba_                | Brit. and Ind. Mus.  | Schizotype.  |
+---------------------------------+----------------------+--------------+
| [_Spongilla alba_ var.          | Ind. Mus.            |     Type     |
| _bengalensis_]                  |                      |              |
+---------------------------------+----------------------+--------------+
| _Spongilla alba_ var.           | Brit. Mus.           | {Specimens   |
| _cerebellata_                   |                      | {compared    |
|                                 |                      | {with type.  |
+---------------------------------+----------------------+--------------+
| _Spongilla cinerea_             | Brit. and Ind. Mus.  | Schizotype.  |
+---------------------------------+----------------------+--------------+
| [_Spongilla travancorica_]      | Ind. Mus.            |    Type.     |
+---------------------------------+----------------------+--------------+
| _Spongilla hemephydatia_        |   "     "            |      "       |
+---------------------------------+----------------------+--------------+
| _Spongilla crateriformis_       | U.S. Nat. Mus.       |   Co-type.   |
+---------------------------------+----------------------+--------------+
| _Spongilla carteri_             | Brit. and Ind. Mus.  | Schizotype.  |
+---------------------------------+----------------------+--------------+
| _Spongilla carteri_ var.        | Ind. Mus.            |    Type.     |
| _mollis_                        |                      |              |
+---------------------------------+----------------------+--------------+
| _Spongilla carteri_ var.        |  "     "             |      "       |
| _cava_                          |                      |              |
+---------------------------------+----------------------+--------------+
| _Spongilla carteri_ var.        |  "     "             |      "       |
| _lobosa_                        |                      |              |
+---------------------------------+----------------------+--------------+
| _Spongilla fragilis_ subsp.     |  "     "             |      "       |
| _calcuttana_                    |                      |              |
+---------------------------------+----------------------+--------------+
| _Spongilla fragilis_ subsp.     | Amsterdam Mus.       |   Co-type.   |
| _decipiens_                     |                      |              |
+---------------------------------+----------------------+--------------+
| _Spongilla gemina_              | Ind. Mus.            |    Type.     |
+---------------------------------+----------------------+--------------+
| _Spongilla crassissima_         |  "     "             |      "       |
+---------------------------------+----------------------+--------------+
| _Spongilla crassissima_ var.    |  "     "             |      "       |
| _crassior_                      |                      |              |
+---------------------------------+----------------------+--------------+
| _Spongilla bombayensis_         | Brit. and Ind. Mus.  | Schizotype.  |
+---------------------------------+----------------------+--------------+
| _Spongilla indica_              | Ind. Mus.            |    Type.     |
+---------------------------------+----------------------+--------------+
| _Spongilla ultima_              |  "    "              |      "       |
+---------------------------------+----------------------+--------------+
| _Pectispongilla aurea_          |  "    "              |      "       |
+---------------------------------+----------------------+--------------+
| _Ephydatia meyeni_              | Brit. and Ind. Mus.  | Schizotype.  |
+---------------------------------+----------------------+--------------+
| _Dosilia plumosa_               |  "   "  "   "        |      "       |
+---------------------------------+----------------------+--------------+
| _Trochospongilla latouchiana_   | Ind. Mus.            |    Type.     |
+---------------------------------+----------------------+--------------+
| _Trochospongilla phillottiana_  |  "    "              |      "       |
+---------------------------------+----------------------+--------------+
| _Trochospongilla pennsylvanica_ | U.S. Nat. Mus.       |   Co-type.   |
+---------------------------------+----------------------+--------------+
| _Tubella vesparioides_          | Ind. Mus.            |    Type.     |
+---------------------------------+----------------------+--------------+
| _Corvospongilla burmanica_      | Brit. and Ind. Mus.  | Schizotype.  |
+---------------------------------+----------------------+--------------+
| _Corvospongilla lapidosa_       | Ind. Mus.            |    Type.     |
+---------------------------------+----------------------+--------------+
|               INDIAN COELENTERATES OF STAGNANT WATER.                 |
+---------------------------------+----------------------+--------------+
|          HYDROZOA.              |                      |              |
+---------------------------------+----------------------+--------------+
| _Hydra oligactis_               | Not in existence.    |              |
+---------------------------------+----------------------+--------------+
| _Hydra vulgaris_                |  "    "              |              |
+---------------------------------+----------------------+--------------+
| [_Syncoryne filamentata_]       | Ind. Mus.            |    Type.     |
+---------------------------------+----------------------+--------------+
| [_Bimeria vestita_]             | ? Not in existence.  |              |
+---------------------------------+----------------------+--------------+
| [_Irene ceylonensis_]           |  {Hydroid in Ind.}   | Hydroid type |
|                                 |  {Mus.,  Medusa}     |              |
|                                 |  {in Brit. Mus.}     |              |
+---------------------------------+----------------------+--------------+
|         ACTINIARIA.             |                      |              |
+---------------------------------+----------------------+--------------+
| [_Sagartia schilleriana_]       | Ind. Mus.            |    Types.    |
+---------------------------------+----------------------+--------------+
| [_Sagartia schilleriana_        |  "    "              |      "       |
| subsp. _exul_]                  |                      |              |
+---------------------------------+----------------------+--------------+
|                   INDIAN POLYZOA OF STAGNANT WATER.                   |
+---------------------------------+----------------------+--------------+
|       ENTOPROCTA.               |                      |              |
+---------------------------------+----------------------+--------------+
| [_Loxosomatoides colonialis_]   | Ind. Mus.            |    Types.    |
+---------------------------------+----------------------+--------------+
|   ECTOPROCTA CHEILOSTOMATA.     |                      |              |
+---------------------------------+----------------------+--------------+
| [_Membranipora lacroixii_]      | ? Paris Mus.         |              |
+---------------------------------+----------------------+--------------+
| [_Membranipora bengalensis_]    | Ind. Mus.            |    Types.    |
+---------------------------------+----------------------+--------------+
|   ECTOPROCTA STENOSTOMATA.      |                      |              |
+---------------------------------+----------------------+--------------+
| [_Bowerbankia caudata_ subsp.   | Ind. Mus.            |    Types.    |
| _bengalensis_]                  |                      |              |
+---------------------------------+----------------------+--------------+
| _Victorella bengalensis_        |  "    "              |      "       |
+---------------------------------+----------------------+--------------+
| _Hislopia lacustris_            | ? Not in existence.  |              |
+---------------------------------+----------------------+--------------+
| _Hislopia lacustris_ subsp.     | Ind. Mus.            |      "       |
| _moniliformis_                  |                      |              |
+---------------------------------+----------------------+--------------+
|   ECTOPROCTA PHYLACTOLÆMATA.    |                      |              |
+---------------------------------+----------------------+--------------+
| _Fredericella indica_           | Ind. Mus.            |    Type.     |
+---------------------------------+----------------------+--------------+
| _Plumatella fruticosa_          | Not in existence.    |              |
+---------------------------------+----------------------+--------------+
| _Plumatella diffusa_            |?Philadelphia Acad.[J]|              |
+---------------------------------+----------------------+--------------+
| _Plumatella allmani_            | Not in existence.    |              |
+---------------------------------+----------------------+--------------+
| _Plumatella emarginata_         |  "        "          |              |
+---------------------------------+----------------------+--------------+
|                                 | {Hamburg and}        | One of the   |
| _Plumatella javanica_           | {Ind.  Mus. }        | types.       |
+---------------------------------+----------------------+--------------+
|                                 | {Brit. and Ind.}     | One of the   |
| _Plumatella tanganyikæ_         | {Mus.          }     | types.       |
+---------------------------------+----------------------+--------------+
| _Stolella indica_               | Ind. Mus.            |    Type.     |
+---------------------------------+----------------------+--------------+
| _Lophopodella carteri_          | Brit. Mus.           |      "       |
+---------------------------------+----------------------+--------------+
| _Lophopodella carteri_ var.     | Ind. Mus.            |      "       |
| _himalayana_                    |                      |              |
+---------------------------------+----------------------+--------------+
| _Pectinatella burmanica_        | Ind. Mus.            |       "      |
+---------------------------------+----------------------+--------------+

     [Footnote J: I have failed to obtain from the Philadelphia
     Academy of Science a statement that the type of this species
     is still in existence.]


The literature dealing with the various groups described in the volume
is discussed in the introductions to the three parts. Throughout the
volume I have, so far as possible, referred to works that can be
consulted in Calcutta in the libraries of the Indian Museum, the
Geological Survey of India, or the Asiatic Society of Bengal. The names
of works that are not to be found in India are marked with a *. The
rarity with which this mark occurs says much for the fortunate position
in which zoologists stationed in Calcutta find themselves as regards
zoological literature, for I do not think that anything essential has
been omitted.

It remains for me to express my gratitude to those who have assisted me
in the preparation of this volume. The names of those who have
contributed specimens for examination have already been mentioned. I
have to thank the Trustees of the Indian Museum not only for their
liberal interpretation of my duties as an officer of the Museum but also
for the use of all the drawings and photographs and some of the blocks
from which this volume is illustrated. Several of the latter have
already been used in the "Records of the Indian Museum." From the Editor
of the "Fauna" I have received valuable suggestions, and I am indebted
to Dr. Weltner of the Berlin Museum for no less valuable references to
literature. Mr. F. H. Gravely, Assistant Superintendent in the Indian
Museum, has saved me from several errors by his criticism.

The majority of the figures have been drawn by the draftsmen of the
Indian Museum, Babu Abhoya Charan Chowdhary, and of the Marine Survey of
India, Babu Shib Chandra Mondul, to both of whom I am much indebted for
their accuracy of delineation.

No work dealing with the sponges of India would be complete without a
tribute to the memory of H. J. Carter, pioneer in the East of the study
of lower invertebrates, whose work persists as a guide and an
encouragement to all of us who are of the opinion that biological
research on Indian animals can only be undertaken in India, and that
even systematic zoological work can be carried out in that country with
success. I can only hope that this, the first volume in the official
Fauna of the Indian Empire to be written entirely in India, may prove
not unworthy of his example.

Indian Museum, Calcutta      Oct. 23rd, 1910.




PART I.

FRESHWATER SPONGES

(SPONGILLIDÆ).




INTRODUCTION TO PART I.


I.

THE PHYLUM PORIFERA.

The phylum Porifera or Spongiæ includes the simplest of the Metazoa or
multicellular animals. From the compound Protozoa its members are
distinguished by the fact that the cells of which they are composed
exhibit considerable differentiation both in structure and in function,
and are associated together in a definite manner, although they are not
combined to form organs and systems of organs as in the higher Metazoa.
Digestion, for instance, is performed in the sponges entirely by
individual cells, into the substance of which the food is taken, and the
products of digestion are handed on to other cells without the
intervention of an alimentary canal or a vascular system, while there is
no structure in any way comparable to the nervous system of more highly
organized animals.

The simplest form of sponge, which is known as an olynthus, is a hollow
vase-like body fixed at one end to some solid object, and with an
opening called the osculum at the other. The walls are perforated by
small holes, the pores, from which the name Porifera is derived.

Externally the surface is protected by a delicate membrane formed of
flattened cells and pierced by the pores, while the interior of the vase
is covered with curious cells characteristic of the sponges, and known
as choanocytes or collar-cells. They consist of minute oval or
pear-shaped bodies, one end of which is provided with a rim or collar of
apparently structureless membrane, while a flagellum or whip-like lash
projects from the centre of the surface surrounded by the collar. These
collar-cells are practically identical with those of which the Protozoa
known as Choanoflagellata consist; but it is only in the sponges[K] that
they are found constantly associated with other cells unlike themselves.

     [Footnote K: Except in "_Proterospongia_," an organism of
     doubtful affinities but not a sponge. It consists of a mass
     of jelly containing ordinary cells, with collar-cells
     _outside_.]

In addition to the collar-cells, which form what is called the gastral
layer, and the external membrane (the derma or dermal membrane), the
sponge contains cells of various kinds embedded in a structureless
gelatinous substance, through which they have the power of free
movement. Most of these cells have also the power of changing their form
in an "amoeboid" manner; that is to say, by projecting and withdrawing
from their margin mobile processes of a more or less finger-like form,
but unstable in shape or direction. The protoplasm of which some of the
cells are formed is granular, while that of others is clear and
translucent. Some cells, which (for the time being at any rate) do not
exhibit amoeboid movements, are glandular in function, while others
again give rise in various ways to the bodies by means of which the
sponge reproduces its kind. There is evidence, however, that any one
kind of cell, even those of the membrane and the gastral layer, can
change its function and its form in case of necessity.

Most sponges possess a supporting framework or skeleton. In some it is
formed entirely of a horny substance called spongin (as in the
bath-sponge), in others it consists of spicules of inorganic matter
(either calcareous or siliceous) secreted by special cells, or of such
spicules bound together by spongin. Extraneous objects, such as
sand-grains, are frequently included in the skeleton. The spongin is
secreted like the spicules by special cells, but its chemical structure
is much more complicated than that of the spicules, and it is not
secreted (at any rate in most cases) in such a way as to form bodies of
a definite shape. In the so-called horny sponges it resembles the chitin
in which insects and other arthropods are clothed.

       *     *     *     *     *

In no adult sponge do the collar-cells completely cover the whole of the
internal surface, the olynthus being a larval form, and by no means a
common larval form. It is only found in certain sponges with calcareous
spicules. As the structure of the sponge becomes more complicated the
collar-cells are tucked away into special pockets or chambers known as
ciliated chambers, and finally the approach to these chambers, both from
the external surface and from the inner or gastral cavity, takes the
form of narrow tubes or canals instead of mere pores. With further
complexity the simple internal cavity tends to disappear, and the sponge
proliferates in such a way that more than one osculum is formed. In the
class Demospongiæ, to which the sponges described in this volume belong,
the whole system is extremely complicated.

The skeleton of sponges, when it is not composed wholly of spongin,
consists of, or at any rate contains, spicules that have a definite
chemical composition and definite shapes in accordance with the class,
order, family, genus, and species of the sponge. Formerly sponges were
separated into calcareous, siliceous, and horny sponges by the nature of
their skeleton; and although the system of classification now adopted
has developed into a much more complex one and a few sponges are known
that have both calcareous and siliceous spicules, the question whether
the spicules are formed of salts of lime or of silica (strictly speaking
of opal) is very important. All Demospongiæ that have spicules at all
have them of the latter substance, and the grade Monaxonida, in which
the freshwater sponges constitute the family Spongillidæ, is
characterized by the possession of spicules that have typically the form
of a needle pointed at both ends. Although spicules of this simple form
may be absent in species that belong to the grade, the larger spicules,
which are called megascleres, have not normally more than one main axis
and are always more or less rod-like in outline. They are usually
arranged so as to form a reticulate skeleton. Frequently, however, the
megascleres or skeleton-spicules are not the only spicules present, for
we find smaller spicules (microscleres) of one or more kinds lying loose
in the substance of the sponge and in the external membrane, or, in the
Spongillidæ only, forming a special armature for the reproductive bodies
known as gemmules.

All sponges obtain their food in the same way, namely by means of the
currents of water set up by the flagella of the collar-cells. These
flagella, although apparently there is little concerted action among
them, cause by their rapid movements changes of pressure in the water
contained in the cavities of the sponge. The water from outside
therefore flows in at the pores and finally makes its way out of the
oscula. With the water minute particles of organic matter are brought
into the sponge, the collar-cells of which, and probably other cells,
have the power of selecting and engulfing suitable particles. Inside the
cells these particles undergo certain chemical changes, and are at least
partially digested. The resulting substances are then handed on directly
to other cells, or, as some assert, are discharged into the common
jelly, whence they are taken up by other cells.

Sponges reproduce their kind in more ways than one, _viz._, by means of
eggs (which are fertilized as in other animals by spermatozoa), by means
of buds, and by means of the peculiar bodies called gemmules the
structure and origin of which is discussed below (p. 42). They are of
great importance in the classification of the Spongillidæ. Sponges can
also be propagated artificially by means of fission, and it is probable
that this method of reproduction occurs accidentally, if not normally,
in natural circumstances.


GENERAL STRUCTURE OF THE SPONGILLIDÆ.

It would be impracticable in this introduction to give a full account of
the structure of the Spongillidæ, which in some respects is still
imperfectly known. Students who desire further information should
consult Professor Minchin's account of the sponges in Lankester's
'Treatise on Zoology,' part ii, or, if a less technical description is
desired, Miss Sollas's contribution to the 'Cambridge Natural History,'
vol. i, in which special attention is paid to _Spongilla_.

The diagram reproduced in fig. 1 gives a schematic view of a vertical
section through a living freshwater sponge. Although it represents the
structure of the organism as being very much simpler than is actually
the case, and entirely omits the skeleton, it will be found useful as
indicating the main features of the anatomy.

[Illustration: Fig. 1.--Diagram of a vertical section through a
freshwater sponge (_modified from Kükenthal_).

A=pores; B=subdermal cavity; C=inhalent canal; D=ciliated chamber;
E=exhalent canal; F=osculum; G=dermal membrane; H=eggs; J=gemmule.]

It will be noted that the diagram represents an individual with a single
osculum or exhalent aperture. As a rule adult Demospongiæ have several
or many oscula, but even in the Spongillidæ sponges occur in which there
is only one. New oscula are formed by a kind of proliferation that
renders the structure still more complex than it is when only one
exhalent aperture is present.

The little arrows in the figure indicate the direction of the currents
of water that pass through the sponge. It enters through small holes in
the derma into a subdermal cavity, which separates the membrane from the
bulk of the sponge. This space differs greatly in extent in different
species. From the subdermal space the water is forced by the action of
the flagella into narrow tubular canals that carry it into the ciliated
chambers. Thence it passes into other canals, which communicate with
what remains of the central cavity, and so out of the oscula.

The ciliated chambers are very minute, and the collar-cells excessively
so. It is very difficult to examine them owing to their small size and
delicate structure. Fig. 2 D represents a collar-cell of a sponge seen
under a very high power of the microscope in ideal conditions.

[Illustration: Fig. 2.--Sponge cells.

A=bubble-cells of _Ephydatia mülleri_, × 350 (_after Weltner_).
B=gemmule-cell of _Spongilla lacustris_ containing green corpuscles
(shaded dark), × 800 (_after Weltner_). C=gemmule-cell of _Ephydatia
blembingia_ showing "tabloids" of food-material, × 1150 (_after Evans_).
D=collar-cell of _Esperella ægagrophila_, × 1600 (_after Vosmaer and
Pekelharing_). E=three stages in the development of a gemmule-spicule of
_E. blembingia_ (_after Evans_), × 665. F=outline of porocytes of _S.
proliferens_, × ca. 1290: _e_=dermal cell; _n_=nucleus; _p_=pore;
_p.c._=pore-cell.]

The nature of the inhalent apertures in the external membrane has been
much discussed as regards the Demospongiæ, but the truth seems to be
that their structure differs considerably even in closely allied
species. At any rate this is the case as regards the Indian _Spongillæ_.
In all species the membrane is composed of flattened cells of irregular
shape fitted together like the pieces of a puzzle-picture. In some
species (e. g., _Spongilla carteri_) the apertures in the membrane
consist merely of spaces between adjacent cells, which may be a little
more crowded together than is usual. But in others (e. g., _Spongilla
proliferens_ and _Spongilla crassissima_) in which the pores are
extremely small, each pore normally pierces the middle of a flat,
ring-shaped cell or porocyte. Occasionally, however, a pore may be found
that is enclosed by two narrow, crescent-shaped cells joined together at
their tips to form a ring. The porocytes of sponges like _Spongilla
carteri_ are probably not actually missing, but instead of being in the
external membrane are situated below the derma at the external entrance
to the canals that carry water to the flagellated chambers or even at
the entrance to the chambers themselves[L]. Some authors object on
theoretical grounds to the statement that porocytes exist in the
Demospongia, and it is possible that these cells have in this grade
neither the same origin as, nor a precisely similar function to, the
porocytes of other sponges. When they occur in the dermal membrane no
great difficulty is experienced in seeing them under a sufficiently high
power of the microscope, if the material is well preserved and mounted
and stained in a suitable manner[M]. In most sponges the porocytes can
contract in such a way that the aperture in their centre is practically
closed, but this power appears to be possessed by the porocytes of
_Spongilla_ only to a very limited extent, although they closely
resemble the porocytes of other sponges in appearance.

     [Footnote L: _Cf._ Weltner, "Spongillidenstudien, V," Arch.
     Naturg. Berlin, lxxiii (i), p. 273 (1907).]

     [Footnote M: It is difficult to see any trace of them in
     thin microtome sections. A fragment of the membrane must be
     mounted whole.]

The external membrane in many Spongillidæ is prolonged round and above
the oscula so as to form an oscular collar. This structure is highly
contractile, but cannot close together. As a rule it is much more
conspicuous in living sponges than in preserved specimens.

It is not necessary to deal here with most of the cells that
occur in the parenchyma or gelatinous part of the sponge. A full
list of the kinds that are found is given by Dr. Weltner in his
"Spongillidenstudien, V," p. 276 (Arch. Naturg. Berlin, lxxiii (i),
1907). One kind must, however, be briefly noticed as being of some
systematic importance, namely the "bubble-cells" (fig. 2 A) that are
characteristic of some species of _Ephydatia_ and other genera. These
cells are comparatively large, spherical in form; each of them contains
a globule of liquid which not only occupies the greater part of the
cell, but forces the protoplasm to assume the form of a delicate film
lining the cell-wall and covering the globule. In optical section
"bubble-cells" have a certain resemblance to porocytes, but the cell is
of course imperforate and not flattened.


SKELETON AND SPICULES.

[Illustration: Fig. 3.--Radial sections of fragments of the skeletons of
_Spongillæ_.

A, _S. crassissima_ var. _crassior_ (from Rajshahi); B, _S. carteri_
(from Calcutta); _a_=transverse, _b_=radiating fibres; _e_=external
surface of the sponge.]

In the Spongillidæ the spicules and the skeleton are more important as
regards the recognition of genera and species than the soft parts. The
skeleton is usually reticulate, but sometimes consists of a mass of
spicules almost without arrangement. The amount of spongin present is
also different in different species. The spicules in a reticulate
skeleton are arranged so as to form fibres of two kinds--radiating
fibres, which radiate outwards from the centre of the sponge and
frequently penetrate the external membrane, and transverse fibres, which
run across from one radiating fibre to another. The fibres are composed
of relatively large spicules (megascleres) arranged parallel to one
another, overlapping at the ends, and bound together by means of a more
or less profuse secretion of spongin. In some species they are actually
enclosed in a sheath of this substance. The radiating fibres are usually
more distinct and stouter than the transverse ones, which are often
represented by single spicules but are sometimes splayed out at the ends
so as to assume in outline the form of an hour-glass (fig. 3 B). The
radiating fibres frequently raise up the membrane at their free
extremities just as a tent-pole does a tent.

Normal spicules of the skeleton are always rod-like or needle-like, and
either blunt or pointed at both ends; they are either smooth, granular,
or covered with small spines. Sometimes spicules of the same type form a
more or less irregular transverse network at the base or on the surface
of the sponge.

[Illustration: Fig. 4.--Part of an oscular collar of _Spongilla
lacustris_ subsp. _reticulata_, showing arrangement of microscleres in
the derma (magnified).]

From the systematist's point of view, the structure of the free spicules
found scattered in the substance and membrane of the sponge, and
especially of those that form the armature of the gemmules, is of more
importance than that of the skeleton-spicules. Free spicules are absent
in many species; when present they are usually needle-like and pointed
at the tips. In a few species, however, they are of variable or
irregular form, or consist of several or many shafts meeting in a common
central nodule. In one genus (_Corvospongilla_) they resemble a double
grappling-iron in form, having a circle of strongly recurved hooks at
both ends. The free microscleres, or flesh-spicules as they are often
called, are either smooth, granular, or spiny.

Gemmule-spicules, which form a characteristic feature of the
Spongillidæ, are very seldom absent when the gemmules are mature. They
are of the greatest importance in distinguishing the genera. In their
simplest form they closely resemble the free microscleres, but in
several genera they bear, either at or near one end or at or near both
ends, transverse disks which are either smooth or indented round the
edge. In one genus (_Pectispongilla_) they are provided at both ends not
with disks but with vertically parallel rows of spines resembling combs
in appearance.

The simpler spicules of the Spongillidæ are formed in single cells (see
fig. 2 E), but those of more complicated shape are produced by several
cells acting in concert. Each spicule, although it is formed mainly of
hydrated silica (opal), contains a slender organic filament running
along its main axis inside the silica. This filament, or rather the tube
in which it is contained, is often quite conspicuous, and in some
species (e. g., _Spongilla crassissima_) its termination is marked at
both ends of the megasclere by a minute conical protuberance in the
silica.

Unless sponges are alchemists and can transmute one element into
another, the material of which the spicules are made must ultimately
come from the water in which the sponges live, or the rocks or other
bodies to or near which they are attached. The amount of water that must
pass through a large specimen of such a sponge as _Spongilla carteri_ in
order that it may obtain materials for its skeleton must be enormous,
for silica is an insoluble substance. I have noticed, however, that this
sponge is particularly abundant and grows with special luxuriance in
ponds in which clothes are washed with soap, and my friend Mr. G. H.
Tipper has suggested to me that possibly the alkali contained in the
soap-suds may assist the sponge in dissolving out the silica contained
in the mud at the bottom of the ponds. The question of how the mineral
matter of the skeleton is obtained is, however, one about which we know
nothing definite.

The spongin that binds the skeleton-spicules together takes the form of
a colourless or yellowish transparent membrane, which is often
practically invisible. When very abundant it sometimes extends across
the nodes of the skeleton as a delicate veil. In some sponges it also
forms a basal membrane in contact with the object to which the sponge is
attached, and in some such cases the spongin of the radiating fibres is
in direct continuity with that of the basal membrane.


COLOUR AND ODOUR.

Most freshwater sponges have a bad odour, which is more marked in some
species than in others. This odour is not peculiar to the Spongillidæ,
for it is practically identical with that given out by the common marine
sponge _Halichondria panicea_. Its function is probably protective, but
how it is produced we do not know.

The coloration of freshwater sponges is usually dull and uniform, but
_Pectispongilla aurea_ is of the brilliant yellow indicated by its name,
while many species are of the bright green shade characteristic of
chlorophyll, the colouring matter of the leaves of plants. Many species
are brown or grey, and some are almost white.

These colours are due to one of three causes, or to a combination of
more than one of them, viz.:--(1) the inhalation of solid inorganic
particles, which are engulfed by the cells; (2) the presence in the
cells of coloured substances, solid or liquid, produced by the vital
activities of the sponge; and (3) the presence in the cells of peculiar
organized living bodies known as "green corpuscles."

Sponges living in muddy water are often nearly black. This is because
the cells of their parenchyma are gorged with very minute solid
particles of silt. If a sponge of the kind is kept in clean water for a
few days, it often becomes almost white. An interesting experiment is
easily performed to illustrate the absorption and final elimination of
solid colouring matter by placing a living sponge (small specimens of
_Spongilla carteri_ are suitable) in a glass of clean water, and
sprinkling finely powdered carmine in the water. In a few hours the
sponge will be of a bright pink colour, but if only a little carmine is
used at first and no more added, it will regain its normal greyish hue
in a few days.

The colouring matter produced by the sponge itself is of two
kinds--pigment, which is probably a waste product, and the substances
produced directly by the ingestion of food or in the process of its
digestion. When pigment is produced it takes the form of minute granules
lying in the cells of the parenchyma, the dermal membrane being as a
rule colourless. Very little is known about the pigments of freshwater
sponges, and even less about the direct products of metabolism. It is
apparently the latter, however, that give many otherwise colourless
sponges a slight pinkish or yellowish tinge directly due to the presence
in cells of the parenchyma of minute liquid globules. In one form of
_Spongilla carteri_ these globules turn of a dark brown colour if
treated with alcohol. The brilliant colour of _Pectispongilla aurea_ is
due not to solid granules but to a liquid or semi-liquid substance
contained in the cells.

The green corpuscles of the Spongillidæ are not present in all species.
There is every reason to think that they represent a stage in the
life-history of an alga, and that they enter the sponge in an active
condition (see p. 49).

A fourth cause for the coloration of freshwater sponges may be noted
briefly. It is not a normal one, but occurs commonly in certain forms
(e. g., _Spongilla alba_ var. _bengalensis_). This cause is the growth
in the canals and substance of the sponge of parasitic algaæ, which turn
the whole organism of a dull green colour. They do not do so, however,
until they have reduced it to a dying state. The commonest parasite of
the kind is a filamentous species particularly common in brackish water
in the Ganges delta.


EXTERNAL FORM AND CONSISTENCY.

[Illustration: Fig. 5.--Part of a type-specimen of _Spongilla lacustris_
subsp. _reticulata_ (nat. size).]

The external form of sponges is very variable, but each species,
subspecies, or variety of the Spongillidæ has normally a characteristic
appearance. The European race of _Spongilla lacustris_, for example,
consists in favourable circumstances of a flattened basal part from
which long cylindrical branches grow out; while in the Indian race of
the species these branches are flattened instead of being cylindrical,
and anastomose freely. The structure of the branches is identical with
that of the basal part. Many other species (for instance, _Spongilla
bombayensis_ and _S. ultima_) never produce branches but always consist
of lichenoid or cushion-shaped masses. The appearance of _Spongilla
crateriformis_, when it is growing on a flattened surface which allows
it to develop its natural form, is very characteristic, for it consists
of little flattened masses that seem to be running out towards one
another, just as though the sponge had been dropped, spoonful by
spoonful, in a viscous condition from a teaspoon. Some species, such as
_Trochospongilla phillottiana_, cover large areas with a thin film of
uniform thickness, while others (e. g., _Spongilla alba_ and _Ephydatia
meyeni_) consist of irregular masses, the surface of which bears
numerous irregular ridges or conical, subquadrate, or digitate
processes. In a few forms (e. g., _Corvospongilla burmanica_) the
surface is covered with small turret-like projections of considerable
regularity, and some (e. g., _Spongilla crassissima_) naturally assume a
spherical or oval shape with an absolutely smooth surface.

The production of long branches is apparently rare in tropical
freshwater sponges.

The form of the oscula is characteristic in many cases. No other Indian
species has them so large, or with such well-defined margins as
_Spongilla carteri_ (Pl. II, fig. 1). In many species (Pl. II, fig. 3)
they have a stellate appearance owing to the fact that grooves in the
substance of the sponge radiate round them beneath the external
membrane. In other species they are quite inconspicuous and very small.

[Illustration: Fig. 6.--Radial section through part of a dried sponge of
_Spongilla crassissima_ (from Calcutta), × 5.]

Spongillidæ differ greatly in consistency. _Spongilla crassissima_ and
_Corvospongilla lapidosa_ are almost stony, although the former is
extremely light, more like pumice than true stone. Other species (e. g.,
_Trochospongilla latouchiana_) are hard but brittle, while others again
are soft and easily compressed, as _Spongilla lacustris_, the variety
_mollis_ of _S. carteri_, and _S. crateriformis_. The consistency of a
sponge depends on two factors--the number of spicules present, and the
amount of spongin. In _Corvospongilla lapidosa_ the number of spicules
is very large indeed. They are not arranged so as to form a reticulate
skeleton but interlock in all directions, and there is hardly any
spongin associated with them. In _Spongilla crassissima_, on the other
hand, the number of spicules although large is not unusually so; but
they form a very definitely reticulate skeleton, and are bound together
by an unusually profuse secretion of spongin. In _S. carteri_ var.
_mollis_ both spicules and spongin are reduced to a minimum, and the
parenchyma is relatively more bulky than usual.


VARIATION.

Sponges are very variable organisms, and even a slight change in the
environment of the freshwater species often produces a considerable
change in form and structure. Some species vary in accordance with the
season, and others without apparent cause. Not only have many given rise
to subspecies and "varieties" that possess a certain stability, but most
if not all are liable to smaller changes that apparently affect both the
individual and the breed, at any rate for a period.

(a) _Seasonal Variation._

Weltner has shown in a recent paper (Arch. Natg. Berlin, lxxiii (i), p.
276, 1907) that in Europe those individuals of _Ephydatia_ which are
found (exceptionally) in an active condition in winter differ
considerably both as regards the number of their cells and their anatomy
from those found in summer. In Calcutta the majority of the individuals
of _Spongilla carteri_ that are found in summer have their external
surface unusually smooth and rounded, and contain in their parenchyma
numerous cells the protoplasm of which is gorged with liquid. These
cells give the whole sponge a faint pinkish tinge during life; but if it
is plunged in spirit, both the liquid in the cells and the spirit turn
rapidly of a dark brown colour. Specimens of _Spongilla crateriformis_
taken in a certain tank in Calcutta during the cold weather had the
majority of the skeleton-spicules blunt, while the extremities of the
gemmule-spicules were distinctly differentiated. Specimens of the same
species taken from the same tank in July had the skeleton-spicules
pointed, while the extremities of the gemmule-spicules were much less
clearly differentiated. I have been unable to confirm this by
observations made on sponges from other tanks, but it would certainly
suggest that at any rate the breed of sponges in the tank first
investigated was liable to seasonal variation.

(b) _Variation due directly to Environment._

The characteristic external form of freshwater sponges is liable in most
cases to be altered as a direct result of changes in the environment.
The following are two characteristic instances of this phenomenon.

Certain shrubs with slender stems grow in the water at the edge of
Igatpuri Lake. The stems of these shrubs support many large examples of
_Spongilla carteri_, which are kept in almost constant motion owing to
the action of the wind on those parts of the shrubs that are not under
water. The surface of the sponges is so affected by the currents of
water thus set up against it that it is covered with deep grooves and
high irregular ridges like cockscombs. Less than a hundred yards from
the lake there is a small pond in which _Spongilla carteri_ is also
abundant. Here it grows on stones at the bottom and has the
characteristic and almost smooth form of the species.

My second instance also refers in part to Igatpuri Lake. _Corvospongilla
lapidosa_ is common in the lake on the lower surface of stones, and also
occurs at Nasik, about thirty miles away, on the walls of a conduit of
dirty water. In the latter situation it has the form of large sheets of
a blackish colour, with the surface corrugated and the oscula
inconspicuous, while in the clear waters of the lake it is of a pale
yellowish colour, occurs in small lichenoid patches, and has its oscula
rendered conspicuous, in spite of their minute size, by being raised on
little conical eminences in such a way that they resemble the craters of
volcanoes in miniature.

Both the European and the Indian races of _Spongilla lacustris_ fail to
develop branches if growing in unfavourable conditions. In specimens
obtained from the River Spree near Berlin these structures are sometimes
many inches in length; while in mature specimens taken under stones in
Loch Baa in the Island of Mull the whole organism consisted of a minute
cushion-shaped mass less than an inch in diameter, and was also
deficient in spicules. Both these breeds belong to the same species, and
probably differ as a direct result of differences in environment.

(c) _Variation without apparent cause._

Plate I in this volume illustrates an excellent example of variation in
external form to which it is impossible to assign a cause with any
degree of confidence. The three specimens figured were all taken in the
same pond, and at the same season, but in different years. It is
possible that the change in form, which was not peculiar to a few
individuals but to all those in several adjacent ponds, was due to a
difference in the salinity of the water brought about by a more or less
abundant rainfall; but of this I have been able to obtain no evidence in
succeeding years.

Many Spongillidæ vary without apparent cause as regards the shape, size,
and proportions of their spicules. This is the case as regards most
species of _Euspongilla_ and _Ephydatia_, and is a fact to which careful
consideration has to be given in separating the species.


NUTRITION.

Very little is known about the natural food of freshwater sponges,
except that it must be of an organic nature and must be either in a very
finely divided or in a liquid condition. The cells of the sponge seem to
have the power of selecting suitable food from the water that flows past
them, and it is known that they will absorb milk. The fact that they
engulf minute particles of silt does not prove that they lack the power
of selection, for extraneous matter is taken up by them not only as food
but in order that it may be eliminated. Silt would soon block up the
canals and so put a stop to the vital activity of the sponge, if it were
not got rid of, and presumably it is only taken into the cells in order
that they may pass it on and finally disgorge it in such a way or in
such a position that it may be carried out of the oscula. The siliceous
part of it may be used in forming spicules.

It is generally believed that the green corpuscles play an important
part in the nutrition of those sponges in which they occur, and there
can be no doubt that these bodies have the power peculiar to all
organisms that produce chlorophyll of obtaining nutritive substances
direct from water and carbonic oxide through the action of sunlight.
Possibly they hand on some of the nourishment thus obtained to the
sponges in which they live, or benefit them by the free oxygen given out
in the process, but many Spongillidæ do well without them, even when
living in identical conditions with species in which they abound.


REPRODUCTION.

Both eggs and buds are produced by freshwater sponges (the latter rarely
except by one species), while their gemmules attain an elaboration of
structure not observed in any other family of sponges.

Probably all Spongillidæ are potentially monoecious, that is to say,
able to produce both eggs and spermatozoa. In one Indian species,
however, in which budding is unusually common (viz. _Spongilla
proliferens_), sexual reproduction takes place very seldom, if ever. It
is not known whether the eggs of sponges are fertilized by spermatozoa
from the individual that produces the egg or by those of other
individuals, but not improbably both methods of fertilization occur.

The egg of a freshwater sponge does not differ materially from that of
other animals. When mature it is a relatively large spherical cell
containing abundant food-material and situated in some natural cavity of
the sponge. In the earlier stages of its growth, however, it exhibits
amoeboid movements, and makes its way through the common jelly. As it
approaches maturity it is surrounded by other cells which contain
granules of food-material. The food-material is apparently transferred
by them in a slightly altered form to the egg. The egg has no shell, but
in some species (e. g. _Ephydatia blembingia_[N]) it is surrounded,
after fertilization, by gland-cells belonging to the parent sponge,
which secrete round it a membrane of spongin. Development goes on within
the chamber thus formed until the larva is ready to assume a free life.

     [Footnote N: Rec. Ind. Mus. i, p. 269 (1907).]

The spermatozoon is also like that of other animals, consisting of a
rounded head and a lash-like tail, the movements of which enable it to
move rapidly through the water. Spermatozoa are produced in _Spongilla_
from spherical cells not unlike the eggs in general appearance. The
contents of these cells divide and subdivide in such a way that they
finally consist of a mass of spermatozoa surrounded by a single covering
cell, which they finally rupture, and so escape.

[Illustration: Fig. 7.--Diagram of a vertical section through the
gemmule of _Spongilla proliferens_.

A=cellular contents; B=internal chitinous layer; C=external chitinous
layer; D=pneumatic coat; E=gemmule-spicule; F=external membrane;
G=foraminal tubule.]

Gemmules are asexual reproductive bodies peculiar to the sponges, but
not to the Spongillidæ. They resemble the statoblasts of the
phylactolæmatous polyzoa in general structure as well as in function,
which is mainly that of preserving the race from destruction by such
agencies as drought, starvation, and temperatures that are either too
high or too low for its activities. This function they are enabled to
perform by the facts that they are provided with coverings not only very
hard but also fitted to resist the unfavourable agencies to which the
gemmules are likely to be exposed, and that they contain abundant
food-material of which use can be made as soon as favourable conditions
occur again.

Internally the gemmule consists of a mass of cells containing
food-material in what may be called a tabloid form, for it consists of
minutely granular plate-like bodies. These cells are enclosed in a
flask-like receptacle, the walls of which consist of two chitinous
layers, a delicate inner membrane and an outer one of considerable
stoutness. The mouth of the flask is closed by an extension of the inner
membrane, and in some species is surrounded by a tubular extension of
the external membrane known as the foraminal tubule. Externally the
gemmule is usually covered by what is called a "pneumatic coat," also of
"chitin" (spongin), but usually of great relative thickness and
honeycombed by spaces which contain air, rendering the structure
buoyant. The pneumatic coat also contains the microscleres
characteristic of the species; it is often limited externally by a third
chitinous membrane, on which more gemmule-spicules sometimes lie
parallel to the surface.

The cells from which those of the gemmules are derived are akin in
origin to those that give rise to eggs and spermatozoa. Some zoologists
are therefore of the opinion that the development of the gemmule is an
instance of parthenogenesis--that is to say of an organism arising from
an egg that has not been fertilized. But some of the collar-cells,
although most of them originate from the external ciliated cells of the
larva, have a similar origin. The building-up of the gemmule affords an
excellent instance of the active co-operation that exists between the
cells of sponges, and of their mobility, for the food-material that has
to be stored up is brought by cells from all parts of the sponge, and
these cells retire after discharging their load into those of the young
gemmule.

The formation of the gemmule of _Ephydatia blembingia_, a Malayan
species not yet found in India, is described in detail by Dr. R. Evans
(Q. J. Microsc. Sci. London, xliv, p. 81, 1901).

Gemmules are produced by the freshwater sponges of Europe, N. America
and Japan at the approach of winter, but in the tropical parts of India
they are formed more frequently at the approach of the hot weather (p.
4). After they are fully formed the sponge that has produced them dies,
and as a rule disintegrates more or less completely. In some species,
however, the greater part of the skeleton remains intact, if it is not
disturbed, and retains some of the gemmules in its meshwork, where they
finally germinate. Other gemmules are set free. Some of them float on
the surface of the water; others sink to the bottom. In any case all of
them undergo a period of quiescence before germinating. It has been
found that they can be kept dry for two years without dying.

The function of the special spicules with which the gemmules of the
Spongillidæ are provided appears to be not only to protect them but more
especially to weight them to the extent suitable to the habits of each
species. Species that inhabit running water, for example, in some cases
have heavier gemmule-spicules than those that live in stagnant water,
and their gemmules are the less easily carried away by the currents of
the river. The gemmules of sponges growing in lakes are sometimes
deficient in spicules. This is the case as regards the form of
_Spongilla lacustris_ found in Lake Baa, Isle of Mull, as regards _S.
helvetica_ from the Lake of Geneva, _S. moorei_ from Lake Tanganyika,
and _S. coggini_ from Tali-Fu in Yunnan; also as regards the species of
_Spongilla_ and _Ephydatia_ found in Lake Baikal, many of the sponges of
which are said never to produce gemmules.

Except in the genus _Corvospongilla_ and the subgenus _Stratospongilla_,
in both of which the air-spaces of the gemmules are usually no more than
cavities between different chitinous membranes, the pneumatic coat is
either "granular" or "cellular." Neither of these terms, however, must
be understood in a physiological sense, for what appear to be granules
in a granular coat are actually minute bubbles of air contained in
little cavities in a foam-like mass of chitin (or rather spongin), while
the cells in a cellular one are only larger and more regular air-spaces
with thin polygonal walls and flat horizontal partitions. The walls of
these spaces are said in some cases to contain a considerable amount of
silica.

The gemmules with their various coverings are usually spherical in
shape, but in some species they are oval or depressed in outline. They
lie as a rule free in the substance of the sponge, but in some species
adhere at its base to the object to which it is attached. In some
species they are joined together in groups, but in most they are quite
free one from another.

Reproductive buds[O] are produced, so far as is known, by very few
Spongillidæ, although they are common enough in some other groups of
sponges. In the only freshwater species in which they have been found to
form a habitual means of reproduction, namely in _Spongilla
proliferens_, they have much the appearance of abortive branches, and it
is possible that they have been overlooked for this reason in other
species, for they were noticed by Laurent in _Spongilla lacustris_ as
long ago as 1840 (CR. Sé. Acad. Sci. Paris, xi, p. 478). The buds
noticed by Laurent, however, were only produced by very young sponges,
and were of a different nature from those of _S. proliferens_, perhaps
representing a form of fission rather than true budding (see 'Voyage de
la Bonite: Zoophytologie,' Spongiaires, pl. i (Paris, 1844)).

     [Footnote O: Proliferation whereby more than one osculum is
     produced is really a form of budding, but in most sponges
     this has become no longer a mode of reproduction but the
     normal method by which size is increased, and must therefore
     be considered merely as a vegetative process.]

In _Spongilla proliferens_, a common Indian species, the buds arise as
thickenings of the strands of cells accompanying the radiating
spicule-fibres of the skeleton, which project outwards from the surface
of the sponge. The thickenings originate beneath the surface and
contain, at the earliest stage at which I have as yet examined them, all
the elements of the adult organism (_i. e._ flesh-spicules, ciliated
chambers, efferent and afferent canals, parenchyma-cells of various
sorts) except skeleton fibres, gemmules, and a dermal membrane. A
section at this period closely resembles one of an adult sponge, except
that the structure is more compact, the parenchyma being relatively
bulky and the canals of small diameter.

Laurent observed reproduction by splitting in young individuals of
_Spongilla_, but I have not been able to obtain evidence myself that
this method of reproduction occurs normally in Indian species. In
injured specimens of _Spongilla carteri_, however, I have observed a
phenomenon that seems to be rather an abnormal form of budding, little
rounded masses of cells making their way to the ends of the radiating
skeleton fibres and becoming transformed into young sponges, which break
loose and so start an independent existence. Possibly the buds observed
by Laurent in _S. lacustris_ were of a similar nature.


DEVELOPMENT.


(a) _From the Egg._

After fertilization, the egg, lying in its cavity in the sponge,
undergoes a complete segmentation; that is to say, becomes divided into
a number of cells without any residuum remaining. The segmentation,
however, is not equal, for it results in the formation of cells of two
distinct types, one larger and less numerous than the other. As the
process continues a pear-shaped body is produced, solid at the broader
end, which consists of the larger cells, but hollow at the other.
Further changes result in the whole of the external surface becoming
ciliated or covered with fine protoplasmic lashes, each of which arises
from a single small cell; considerable differentiation now takes place
among the cells, and spicules begin to appear. At this stage or earlier
(for there seem to be differences in different species and individuals
as to the stage at which the young sponge escapes) the larva makes its
way out of the parent sponge. After a brief period of free life, in
which it swims rapidly through the water by means of its cilia, it fixes
itself by the broad end to some solid object (from which it can never
move again) and undergoes a final metamorphosis. During this process the
ciliated cells of the external layer make their way, either by a
folding-in of the whole layer or in groups of cells, into the interior,
there change into collar-cells and arrange themselves in special
cavities--the ciliated chambers of the adult. Finally an osculum, pores,
&c., are formed, and the sponge is complete.

This, of course, is the merest outline of what occurs; other changes
that take place during the metamorphosis are of great theoretical
interest, but cannot be discussed here. The student may refer to Dr. R.
Evans's account of the larval development of _Spongilla lacustris_ in
the Q. J. Microsc. Sci. London, xlii, p. 363 (1899).

(b) _From the Gemmule._

The period for which the gemmule lies dormant probably depends to some
extent upon environment and to some extent on the species to which it
belongs. Carter found that if he cleaned gemmules with a handkerchief
and placed them in water exposed to sunlight, they germinated in a few
days; but in Calcutta gemmules of _Spongilla alba_ var. _bengalensis_
treated in this way and placed in my aquarium at the beginning of the
hot weather, did not germinate until well on in the "rains." Even then,
after about five months, only a few of them did so. Zykoff found that in
Europe gemmules kept for two years were still alive and able to
germinate.

Germination consists in the cellular contents of the gemmule bursting
the membrane or membranes in which they are enclosed, and making their
way out of the gemmule in the form of a delicate whitish mass, which
sometimes issues through the natural aperture in the outer chitinous
coat and sometimes through an actual rent in this coat. In the latter
case the development of the young sponge is more advanced than in the
former.

The fullest account of development from the gemmule as yet published is
by Zykoff, and refers to _Ephydatia_ in Europe (Biol. Centralbl. Berlin,
xii, p. 713, 1892).

His investigations show that the bursting of the gemmule is not merely a
mechanical effect of moisture or any such agency but is due to
development of the cellular contents, which at the time they escape have
at least undergone differentiation into two layers. Of the more
important soft structures in the sponge the osculum is the first to
appear, the ciliated chambers being formed later. This is the opposite
of what occurs in the case of the bud, but in both cases the aperture
appears to be produced by the pressure of water in the organism. The
manner and order in which the different kinds of cells originate in the
sponge derived from a gemmule give support to the view that the
primitive cell-layers on which morphologists lay great stress are not of
any great importance so far as sponges are concerned.

(c) _Development of the Bud._

As the bud of _Spongilla proliferens_ grows it makes its way up the
skeleton-fibre to which it was originally attached, pushing the dermal
membrane, which expands with its growth, before it. The skeleton-fibre
does not, however, continue to grow in the bud, in which a number of
finer fibres make their appearance, radiating from a point approximately
at the centre of the mass. As the bud projects more and more from the
surface of the sponge the dermal membrane contracts at its base, so as
finally to separate it from its parent. Further details are given on p.
74.


HABITAT.

Mr. Edward Potts[P], writing on the freshwater sponges of North America,
says:--"These organisms have occasionally been discovered growing in
water unfit for domestic uses; but as a rule they prefer pure water, and
in my experience the finest specimens have always been found where they
are subjected to the most rapid currents." True as this is of the
Spongillidæ of temperate climates, it is hardly applicable to those of
tropical India, for in this country we find many species growing most
luxuriantly and commonly in water that would certainly be considered
unfit for domestic purposes in a country in which sanitation was treated
as a science. Some species, indeed, are only found in ponds of water
polluted by human agency, and such ponds, provided that other conditions
are favourable, are perhaps the best collecting grounds. Other
favourable conditions consist in a due mixture of light and shade, a
lack of disturbance such as that caused by cleaning out the pond, and
above all in the presence of objects suitable for the support of
sponges.

     [Footnote P: P. Ac. Philad. 1887, p. 162.]

I do not know exactly why light and shade must be mixed in a habitat
favourable for the growth of sponges, for most species prefer shade, if
it be not too dense; but it is certainly the case that, with a few
exceptions, Indian Spongillidæ flourish best in water shaded at the
edges by trees and exposed to sunlight elsewhere. One of the exceptions
to this rule is the Indian race of _Spongilla lucustris_, which is found
in small pools of water in sand-dunes without a particle of shade.
Several species are only found on the lower surface of stones and roots
in circumstances which do not suggest that their position merely
protects them from mud, which, as Mr. Potts points out, is their "great
enemy." A notable instance is _Trochospongilla pennsylvanica_, which is
found hiding away from light in America and Europe as well as in India.

It is curious that it should be easy to exterminate the sponges in a
pond by cleaning it out, for one would have thought that sufficient
gemmules would have remained at the edge, or would have been brought
rapidly from elsewhere, to restock the water. Mr. Green has, however,
noted that _Spongilla carteri_ has disappeared for some years from a
small lake at Peradeniya in which it was formerly abundant, owing to the
lake having been cleaned out, and I have made similar observations on
several occasions in Calcutta.

The question of the objects to which sponges attach themselves is one
intimately connected with that of the injury done them by mud. The delta
of the Ganges is one of the muddiest districts on earth. There are no
stones or rocks in the rivers and ponds, but mud everywhere. If a sponge
settles in the mud its canals are rapidly choked, its vital processes
cease, and it dies. In this part of India, therefore, most sponges are
found fixed either to floating objects such as logs of wood, to vertical
objects such as the stems of bulrushes and other aquatic plants, or to
the tips of branches that overhang the water and become submerged during
the "rains." In Calcutta man has unwittingly come to the assistance of
the sponges, not only by digging tanks but also by building
"bathing-ghats" of brick at the edge, and constructing, with æsthetic
intentions if not results, masses of artificial concrete rocks in or
surrounding the water. There are at least two sponges (the typical form
of _Spongilla alba_ and _Ephydatia meyeni_) which in Calcutta are only
found attached to such objects. The form of _S. alba_, however, that is
found in ponds of brackish water in the Gangetic delta has not derived
this artificial assistance from man, except in the few places where
brick bridges have been built, and attaches itself to the stem and roots
of a kind of grass that grows at the edge of brackish water. This sponge
seems to have become immune even to mud, the particles of which are
swallowed by its cells and finally got rid of without blocking up the
canals.

Several Indian sponges are only found adhering to stones and rocks.
Among these species _Corvospongilla lapidosa_ and our representatives of
the subgenus _Stratospongilla_ are noteworthy. Some forms (e. g.
_Spongilla carteri_ and _S. crateriformis_) seem, however, to be just as
much at home in muddy as in rocky localities, although they avoid the
mud itself.

There is much indirect evidence that the larvæ of freshwater sponges
exercise a power of selection as regards the objects to which they affix
themselves on settling down for life.

Few Spongillidæ are found in salt or brackish water, but _Spongilla
alba_ var. _bengalensis_ has been found in both, and is abundant in the
latter; indeed, it has not been found in pure fresh water. _Spongilla
travancorica_ has only been found in slightly brackish water, while _S.
lacustris_ subsp. _reticulata_ and _Dosilia plumosa_ occur in both fresh
and brackish water, although rarely in the latter. The Spongillidæ are
essentially a freshwater family, and those forms that are found in any
but pure fresh water must be regarded as aberrant or unusually tolerant
in their habits, not as primitive marine forms that still linger halfway
to the sea.


ANIMALS AND PLANTS COMMONLY ASSOCIATED WITH
FRESHWATER SPONGES.


(a) _Enemies._

Freshwater sponges have few living enemies. Indeed, it is difficult to
say exactly what is an enemy of a creature so loosely organized as a
sponge. There can be little doubt, in any case, that the neuropteroid
larva (_Sisyra indica_) which sucks the cells of several species should
be classed in this category, and it is noteworthy that several species
of the same genus also occur in Europe and N. America which also attack
sponges. Other animals that may be enemies are a midge larva (_Tanypus_
sp.) and certain worms that bore through the parenchyma (p. 93), but I
know of no animal that devours sponges bodily, so long as they are
uninjured. If their external membrane is destroyed, they are immediately
attacked by various little fish and also by snails of the genera
_Limnæa_ and _Planorbis_, and prawns of the genus _Palæmon_.

Their most active and obvious enemy is a plant, not an animal,--to wit,
a filamentous alga that blocks up their canals by its rapid growth (p.
79).

(b) _Beneficial Organisms._

The most abundant and possibly the most important organisms that may be
considered as benefactors to the Spongillidæ are the green corpuscles
that live in the cells of certain species (fig. 2, p. 31), notably
_Spongilla lacustris_, _S. proliferens_, and _Dosilia plumosa_. I have
already said that these bodies are in all probability algæ which live
free in the water and move actively at one stage of their existence, but
some of them are handed on directly from a sponge to its descendants in
the cells of the gemmule. In their quiescent stage they have been
studied by several zoologists, notably by Sir Ray Lankester[Q] and Dr.
W. Weltner[R], but the strongest light that has been cast on their
origin is given by the researches of Dr. F. W. Gamble and Mr. F. Keeble
(Q. J. Microsc. Sci. London, xlvii, p. 363, 1904, and li, p. 167, 1907).
These researches do not refer directly to the Spongillidæ but to a
little flat-worm that lives in the sea, _Convoluta roscoffiensis_. The
green corpuscles of this worm so closely resemble those of _Spongilla_
that we are justified in supposing a similarity of origin. It has been
shown by the authors cited that the green corpuscles of the worm are at
one stage minute free-living organisms provided at one end with four
flagella and at the other with a red pigment spot. The investigators are
of the opinion that these organisms exhibit the essential characters of
the algæ known as Chlamydomonadæ, and that after they have entered the
worm they play for it the part of an excretory system.

     [Footnote Q: Q. J. Microsc. Sci. London, xxii. p. 229
     (1882).]

     [Footnote R: Arch. Naturg. Berlin, lix (i), p. 260 (1893).]

As they exist in the cells of _Spongilla_ the corpuscles are minute oval
bodies of a bright green colour and each containing a highly refractile
colourless granule. A considerable number may be present in a single
cell. It is found in European sponges that they lose their green colour
if the sponge is not exposed to bright sunlight. In India, however,
where the light is stronger, this is not always the case. Even when the
colour goes, the corpuscles can still be distinguished as pale images of
their green embodiment. They are called _Chlorella_ by botanists, who
have studied their life-history but have not yet discovered the full
cycle. See Beyerinck in the Botan. Zeitung for 1890 (vol. xlviii, p.
730, pl. vii; Leipzig), and for further references West's 'British
Freshwater Algæ,' p. 230 (1904).

The list of beneficent organisms less commonly present than the green
corpuscles includes a _Chironomus_ larva that builds parchment-like
tubes in the substance of _Spongilla carteri_ and so assists in
supporting the sponge, and of a peculiar little worm (_Chætogaster
spongillæ_[S]) that appears to assist in cleaning up the skeleton of the
same sponge at the approach of the hot weather and in setting free the
gemmules (p. 93).

     [Footnote S: Journ. As. Soc. Beng. n. s. ii, 1906, p. 189.]

(c) _Organisms that take shelter in the Sponge or adhere to it
externally._

There are many animals which take shelter in the cavities of the sponge
without apparently assisting it in any way. Among these are the little
fish _Gobius alcockii_, which lays its eggs inside the oscula of _S.
carteri_, thus ensuring not only protection but also a proper supply of
oxygen for them (p. 94); the molluscs (_Corbula_, spp.) found inside _S.
alba_ var. _bengalensis_ (p. 78); and the Isopod (_Tachæa
spongillicola_) that makes its way into the oscula of _Spongilla
carteri_ and _S. crateriformis_ (pp. 86, 94).

In Europe a peculiar ciliated Protozoon (_Trichodina spongillæ_) is
found attached to the external surface of freshwater sponges. I have
noticed a similar species at Igatpuri on _Spongilla crateriformis_, but
it has not yet been identified. It probably has no effect, good or bad,
on the sponge.


FRESHWATER SPONGES IN RELATION TO MAN.

In dealing with _Spongilla carteri_ I have suggested that sponges may be
of some hygienic importance in absorbing putrid organic matter from
water used both for ablutionary and for drinking purposes, as is so
commonly the case with regard to ponds in India. Their bad odour has
caused some species of Spongillidæ to be regarded as capable of
polluting water, but a mere bad odour does not necessarily imply that
they are insanitary.

Unless my suggestion that sponges purify water used for drinking
purposes by absorbing putrid matter should prove to be supported by
fact, the Spongillidæ cannot be said to be of any practical benefit to
man. The only harm that has been imputed to them is that of polluting
water[T], of blocking up water-pipes by their growth--a very rare
occurrence,--and of causing irritation to the human skin by means of
their spicules--a still rarer one. At least one instance is, however,
reported in which men digging in a place where a pond had once been were
attacked by a troublesome rash probably due to the presence of
sponge-spicules in the earth, and students of the freshwater sponges
should be careful not to rub their eyes after handling dried specimens.

     [Footnote T: See Potts, Proc. Ac. Philad. 1884, p. 28.]


INDIAN SPONGILLIDÆ COMPARED WITH THOSE OF OTHER COUNTRIES.

In Weltner's catalogue of the freshwater sponges (1895) seventy-six
recent species of Spongillidæ (excluding _Lubosmirskia_) are enumerated,
and the number now known is well over a hundred. In India we have
twenty-nine species, subspecies, and varieties, while from the whole of
Europe only about a dozen are known. In the neighbourhood of Calcutta
nine species, representing three genera and a subgenus, have been found;
all of them occur in the Museum tank. The only other region of similar
extent that can compare with India as regards the richness of its
freshwater sponge fauna is that of the Amazon, from which about twenty
species are known. From the whole of North America, which has probably
been better explored than any other continent so far as Spongillidæ are
concerned, only twenty-seven or twenty-eight species have been recorded.

The Indian species fall into seven genera, one of which (_Spongilla_)
consists of three subgenera. With one exception (that of
_Pectispongilla_, which has only been found in Southern India) these
genera have a wide distribution over the earth's surface, and this is
also the case as regards the subgenera of Spongilla. Four genera
(_Heteromeyenia_, _Acalle_, _Parmula_, and _Uruguaya_) that have not yet
been found in India are known to exist elsewhere.

Five of the Indian species are known to occur in Europe, viz.,
_Spongilla lacustris_, _S. crateriformis_, _S. carteri_, _S. fragilis_,
_Trochospongilla pennsylvanica_; while _Ephydatia meyeni_ is
intermediate between the two commonest representatives of its genus in
the Holarctic Zone, _Ephydatia fluviatilis_ and _E. mülleri_. Of the
species that occur both in India and in Europe, two (_Spongilla
lacustris_ and _S. fragilis_) are found in this country in forms
sufficiently distinct to be regarded as subspecies or local races.
Perhaps this course should also be taken as regards the Indian forms of
_S. carteri_, of which, however, the commonest of the Indian races would
be the typical one; but _S. crateriformis_ and _T. pennsylvanica_ seem
to preserve their specific characters free from modification, whether
they are found in Europe, Asia, or America.

The freshwater sponges of Africa have been comparatively little studied,
but two Indian species have been discovered, _S. bombayensis_ in Natal
and _S. alba_ var. _cerebellata_ in Egypt. Several of the species from
the Malabar Zone are, moreover, closely allied to African forms (p. 11).


FOSSIL SPONGILLIDÆ.

The Spongillidæ are an ancient family. Young described a species
(_Spongilla purbeckensis_) from the Upper Jurassic of Dorset (Geol. Mag.
London (new series) v, p. 220 (1878)), while spicules, assigned by
Ehrenberg to various genera but actually those of _Spongilla lacustris_
or allied forms, have been found in the Miocene of Bohemia (see
Ehrenberg's 'Atlas für Micro-Geologie,' pl. xi (Leipzig, 1854), and
Traxler in Földt. Közl., Budapest, 1895, p. 211). _Ephydatia_ is also
known in a fossil condition, but is probably less ancient than
_Spongilla_.

Ehrenberg found many sponge spicules in earth from various parts of the
Indian Empire (including Baluchistan, Mangalore, Calcutta, the Nicobars
and Nepal) and elsewhere, and it might be possible to guess at the
identity of some of the more conspicuous species figured in his 'Atlas.'
The identification of sponges from isolated spicules is, however, always
a matter of doubt, and in some cases Ehrenberg probably assigned
spicules belonging to entirely different families or even orders to the
same genus, while he frequently attributed the different spicules of the
same species to different genera. Among his fossil (or supposed fossil)
genera that may be assigned to the Spongillidæ wholly or in part are
_Aphidiscus_, _Spongolithis_, _Lithastericus_ and _Lithosphæridium_,
many of the species of these "genera" certainly belonging to _Spongilla_
and _Ephydatia_.


ORIENTAL SPONGILLIDÆ NOT YET FOUND IN INDIA.

Few freshwater sponges that have not been found in India are as yet
known from the Oriental Region, and there is positive as well as
negative evidence that Spongillidæ are less abundant in Malaysia than in
this country. The following list includes the names of those that have
been found, with notes regarding each species. It is quite possible that
any one of them may be found at any time within the geographical
boundaries laid down for this 'Fauna.' I have examined types or co-types
in all cases except that of _Ephydatia fortis_, Weltner.

I. _Spongilla_ (_Euspongilla_) _microsclerifera_*, Annandale
(Philippines). P. U.S. Mus. xxxvii, p. 131 (1909).

This sponge is closely related to _S. lacustris_, but apparently does
not produce branches. It is remarkable for the enormous number of
microscleres in its parenchyma.

II. _S._ (_Euspongilla_) _philippinensis_*, Annandale (Philippines). P.
U.S. Mus. xxxvi, p. 629 (1909).

Related to _S. alba_ and still more closely to _S. sceptrioides_ of
Australia. From the former it is readily distinguished by having
minutely spined megascleres, green corpuscles, slender gemmule-spicules
with short spines and no free microscleres.

III. _S._ (? _Euspongilla_) _yunnanensis_*, Annandale (W. China). Rec.
Ind. Mus. v, p. 197 (1910).

Apparently allied to _S. philippinensis_ but with smooth
skeleton-spicules and a more delicate skeleton.

IV. _S._ (_Stratospongilla_) _sinensis_*, Annandale (Foochow, China). P.
U.S. Mus. xxxviii, p. 183 (1910).

This species and _S. clementis_ are referred to _Stratospongilla_ with
some doubt. Their gemmules are intermediate in structure between those
of that subgenus and those of _Euspongilla_.  In _S. sinensis_ the
gemmules are packed together in groups at the base of the sponge, and
their spicules are smooth, stout, and gradually pointed.

V. _S._ (_Stratospongilla_) _clementis_*, Annandale (Philippines). P.
U.S. Mus. xxxvi, p. 631 (1909).

The gemmules are single and closely adherent at the base of the sponge.
Their spicules are very slender and minutely spined.

VI. _S._ (? _Stratospongilla_) _coggini_*, Annandale (W. China). Rec.
Ind. Mus. v, p. 198 (1910).

The gemmules apparently lack microscleres. They resemble those of _S.
clementis_, to which the species is probably related, in other respects.
The skeleton-spicules are spiny and rather stout, the species being
strongly developed at the two ends.

VII. _S._ (_Stratospongilla_) _sumatrana_*, Weber (Malay Archipelago).
Zool. Ergebnisse einer Reise in Niederländisch Ost-Indien, i. p. 38
(1890).

Closely allied to _S. indica_ (p. 100) but with pointed
skeleton-spicules.

VIII. _Ephydatia fortis_, Weltner (Philippines). Arch. Naturgesch.
lxi(i), p. 141 (1895).

This species is remarkable for the great development of the spines on
the shaft of the gemmule-spicules.

IX. _Ephydatia bogorensis_*, Weber (Malay Archipelago). Zool. Ergebnisse
einer Reise in Niederländisch Ost-Indien, i, p. 33 (1890).

The gemmule-spicules have rather narrow flattish disks, the edge of
which is feebly but closely serrated.

X. _E. blembingia_*, Evans (Malay Peninsula). Q. J. Microsc. Sci.
London, xliv, p. 81 (1901).

The gemmules resemble those of _Dosilia plumosa_ but are spherical.
There are no free microscleres.

XI. _Tubella vesparium_*, v. Martens (Borneo). Arch. Naturg.

Berlin, xxxiv, p. 62 (1868).

Closely related to _T. vesparioides_ (p. 189), but with spiny
megascleres.

As regards _Spongilla decipiens_*, Weber, from the Malay Archipelago,
see p. 97.


II.

HISTORY OF THE STUDY OF FRESHWATER SPONGES.

The bath-sponge was known to the Greeks at an early date, and Homer
refers to it as being used for cleansing furniture, for expunging
writing, and for ablutionary purposes. He also mentions its peculiar
structure, "with many holes." "Many things besides," wrote the English
naturalist Ray in his 'Historia Plantarum' (1686), "regarding the powers
and uses of sponges have the Ancients: to them refer." Ray himself
describes at least one freshwater species, which had been found in an
English river, and refers to what may be another as having been brought
from America. In the eighteenth century Linné, Pallas and other authors
described the commoner European Spongillidæ in general terms, sometimes
as plants and sometimes as animals, more usually as zoophytes or
"plant-animals" partaking of the nature of both kingdoms. The gemmules
were noted and referred to as seeds. The early naturalists of the
Linnæan Epoch, however, added little to the general knowledge of the
Spongillidæ, being occupied with theory in which theological disputes
were involved rather than actual observation, and, notwithstanding the
fact that the animal nature of sponges was clearly demonstrated by
Ellis[U] in 1765, it was not until the nineteenth century was well
advanced that zoologists could regard sponges in anything like an
impartial manner.

          [Footnote U: Phil. Trans. Roy. Soc. lv, p. 280.]

One of the pioneers in the scientific study of the freshwater forms was
the late Dr. H. J. Carter, who commenced his investigations, and carried
out a great part of them, in Bombay with little of the apparatus now
considered necessary, and with a microscope that must have been grossly
defective according to modern ideas. His long series of papers
(1848-1887) published in the 'Annals and Magazine of Natural History' is
an enduring monument to Indian zoology, and forms the best possible
introduction to the study of the Spongillidæ. Even his earlier mistakes
are instructive, for they are due not so much to actual errors in
observation as to a faithful transcription of what was observed with
faulty apparatus.

Contemporary with Carter were two authors whose monographs on the
freshwater sponges did much to advance the study of the group, namely,
J. S. Bowerbank, whose account of the species known at the time was
published in the 'Proceedings of the Zoological Society of London' in
1882, and the veteran American naturalist Mr. Edward Potts, whose study
of the freshwater sponges culminated in his monograph published in the
'Proceedings of the Academy of Natural Sciences of Philadelphia' in
1887. Carter's own revision of the group was published in the 'Annals
and Magazine of Natural History' in 1881. The names of Vejdovsky, who
prefaced Potts's monograph with an account of the European species, and
of Dybowsky, who published several important papers on classification,
should also be mentioned, while Weltner's catalogue of the known species
(1895) is of the greatest possible value to students of the group.

Many authors have dealt with the physiology, reproduction and
development of the Spongillidæ, especially in recent years; Dr. R.
Evans's description of the larva of _Spongilla lacustris_ (1899), and
his account of the development of the gemmule in _Ephydatia blembingia_
(1901), Zykoff's account of the development of the gemmule and of the
sponge from the gemmule (1892), and Weltner's observations on colour and
other points (1893, 1907), may be mentioned in particular. Laurent's
observations on development (1844), which were published in the 'Voyage
de la Bonite,' and especially the exquisite plates which accompany them,
have not received the notice they deserve, probably on account of their
method of publication.


LITERATURE.

The fullest account of the literature on the Spongillidæ as yet
published will be found in the first of Weltner's 'Spongillidenstudien'
(Archiv für Naturgeschichte, lix (i), p. 209, 1893). Unfortunately it
contains no references of later date than 1892. The following list is
not a complete bibliography, but merely a list of books and papers that
should prove of use to students of the Oriental Spongillidæ.

(a) _Works of Reference._

1863. BOWERBANK, "A Monograph of the Spongillidæ," P. Zool. Soc. London,
1863, pp. 440-472, pl. xxxviii.

1867. GRAY, J. E., "Notes on the arrangement of Sponges, with the
description of some new genera." _ibid._ 1867, pp. 492-558.

1881. CARTER, "History and classification of the known species of
_Spongilla_," Ann. Nat. Hist. (5) vii, pp. 77-107, pls. v, vi.

1883. VEJDOVSKY, "Die Süsswasserschwämme Böhmens," Abh. Kön. Böhm. Ges.
Wiss. (math.-natur. Classe), xii, pp. 1-43, pls. i-iii.

1887. VOSMAER, "Spongien (Porifera)," in Bronn's Thier-Reichs.

1887. POTTS, "Contributions towards a synopsis of the American forms of
Fresh-Water Sponges, with descriptions of those named by other authors
and from all parts of the world," P. Ac. Philad. pp. 158-279, pls.
v-xii.

1887. VEJDOVSKY, "Diagnosis of the European Spongillidæ," _ibid._ pp.
172-180.

1888. WIERZEJSKI, "Beitrag zur Kenntnis der Süsswasserschwämme," Verh.
k.-k. zool.-bot. Ges. Wien, xxxviii, pp. 529-536, pl. xii.

1891. WELTNER, in Zacharias's Die Tier- und Pflanzenwelt des
Süsswassers: I, Die Süsswasserschwämme.

1895. WELTNER, "Spongillidenstudien, III," Arch. Naturg. Berlin, lxi
(i), pp. 114-144.

1895. KORSCHELT and HEIDER, Text-book of the Embryology of
Invertebrates: English edition, prepared by E. L. Mark and W. McM.
Woodworth, Vol. I, chap. i.

1900. MINCHIN, Sponges--Phylum Porifera in Lankester's "Treatise on
Zoology," ii.

1905. KÜKENTHAL, W., Leitfaden für das Zoologische Praktikum (3rd Ed.,
Jena), 2. Kursus: Porifera, Schwämme, p. 31.

1906. SOLLAS, I. B. J., Cambridge Natural History--I. Porifera
(Sponges).

1909. WELTNER, "Spongillidæ, Süsswasserschwämme," in Brauer's "Die
Süsswasserfauna Deutschlands," Heft xix, pp. 177-190.

1910. LLOYD, An Introduction to Biology for Students in India.

(b) _Special Memoirs on Anatomy, Physiology, and Development._

1844. LAURENT, "Recherches sur l'Hydre et l'Eponge d'eau douce," Voyage
de la Bonite, ii, pp. 113-276.

1854. CARTER, "Zoosperms in _Spongilla_," Ann. Nat. Hist. (2) xiv, pp.
334-336, pl. xi, figs. 1-6.

1857. CARTER, "On the ultimate structure of _Spongilla_, and additional
notes on Freshwater Infusoria," Ann. Nat. Hist. (2) xx, pp. 21-41, pl.
i, figs. 1-11.

1859. CARTER, "On the identity in structure and composition of the
so-called 'seed-like body' of _Spongilla_ with the winter-egg of the
Bryozoa, and the presence of starch-granules in each," Ann. Nat. Hist.
(3) iii, pp. 331-343, pl. viii.

1859. LIEBERKÜHN, "Neue Beiträge zur Anatomie der Spongien," Arch. Anat.
Phys. J. Müller, pp. 374-375, 526-528.

1871. CARTER, "Discovery of the animal of the Spongiadæ confirmed," Ann.
Nat. Hist. (4) vii, p. 445.

1871. HAECKEL, "Ueber die sexuelle Fortpflanzung und das natürliche
System der Schwämme," Jenaische Zeitschr. f. Naturw. vi, pp. 643, 645.

1874. CARTER, "On the nature of the seed-like body of _Spongilla_; on
the origin of the mother-cell of the spicule; and on the presence of
spermatozoa in the _Spongida_," Ann. Nat. Hist. (4) xiv, pp. 97-111.

1874. LANKESTER, E. RAY, "The mode of occurrence of chlorophyll in
_Spongilla_," Q. J. Micr. Sci. xiv, pp. 400-401.

1875. SORBY, H., "On the Chromatological relations of _Spongilla
fluviatilis_," Q. J. Micr. Sci. xv, pp. 47-52.

1878. GANIN, "Zur Entwickelung der _Spongilla fluviatilis_," Zool. Anz.
I, pp. 195-199.

1882. CARTER, "Spermatozoa, polygonal cell-structure, and the green
colour in _Spongilla_, together with a new species," Ann. Nat. Hist. (5)
x, pp. 362-372, pl. 16.

1882. GEDDES, "Further researches on animals containing chlorophyll,"
Nature, xxv, pp. 303-305, 361-362.

1882. LANKESTER, E. RAY, "On the chlorophyll-corpuscles and amyloid
deposits of _Spongilla_ and _Hydra_," Q. J. Micr. Sci. xxii (n. s.), pp.
229-254, pl. xx.

1883. MARSHALL, W., "Einige vorläutige Bemerkungen über die Gemmulä der
Süsswasserschwämme," Zool. Anz. vi, pp. 630-634, 648-652.

1884. CARTER, "The branched and unbranched forms of the Freshwater
Sponges considered generally," Ann. Nat. Hist. (5) xiii, pp. 269-273.

1884. MARSHALL, W., "Vorläutige Bemerkungen über die
Fortpflanzungsverhältnisse von _Spongilla lacustris_," Ber. Naturf. Ges.
Leipzig,* pp. 22-29.

1884. POTTS, "Freshwater Sponges as improbable causes of the pollution
of river-water," P. Ac. Philad. pp. 28-30.

1885. SCHULZE, F. E., "Über das Verhältniss der Spongien zu den
Choanoflagellaten," SB. preuss. Akad. Wiss. Berlin, pp. 179-191.

1886. GOETTE, Untersuchungen zur Entwickelungsgeschichte von _Spongilla
fluviatilis_*, Hamburg und Leipzig (5 plates).

1886. WIERZEJSKI, "Le développement des Gemmules des Eponges d'eau douce
d'Europe," Arch. Slaves Biologie, i, pp. 26-47 (1 plate).

1887. CARTER, "On the reproductive elements of the _Spongida_," Ann.
Nat. Hist. (5) xix, pp. 350-360.

1889. MAAS, "Zur Metamorphose der Spongillalarve," Zool. Anz. xii, pp.
483-487.

1890. MAAS, "Ueber die Entwickelung des Süsswasserschwämmes," Zeitschr.
Wiss. Zool. 1, pp. 527-554, pls. xxii, xxiii.

1890. WEBER, M. et Mme. A., "Quelques nouveau cas de Symbiose," Zool.
Ergebn. einer Reise Niederländ. Ost-Indien, i, pp. 48-72, pl. v.

1892. ZYKOFF, "Die Entwicklung der Gemmulä der _Ephydatia fluviatilis_
auct.," Zool. Anz. xv, pp. 95-96.

1892. ZYKOFF, "Die Bildung der Gemmulä bei _Ephydatia Fluviatilis_," Revue
Sc. Nat. Soc. St. Pétersbourg,* pp. 342-344.

1892. ZYKOFF, "Die Entwicklung der Gemmulä bei _Ephydatia fluviatilis_
auct.," Bull. Soc. Imp. Natur. Moscou, n. s. vi, pp. 1-16, pl. i, ii.

1892. ZYKOFF, "Entwickelungsgeschichte von _Ephydatia mülleri_, Liebk.
aus den Gemmulæ," Biol. Centralbl. xii, pp. 713-716.

1893. WELTNER, "Spongillidenstudien, II," Arch. Naturg. Berlin, lix (1),
pp. 245-282, pls. viii, ix.

1899. EVANS, R., "The structure and metamorphosis of the larva of
_Spongilla lacustris_," Q. J. Micr. Sci. xlii, pp. 363-476, pls.
xxxv-xli.

1901. EVANS, R., "A description of _Ephydatia blembingia_, with an
account of the formation and structure of the gemmule," Q. J. Micr. Sci.
xliv, pp. 71-109, pls. i-iv.

1907. WELTNER, "Spongillideustudien, V.: Zur Biologie von _Ephydatia
fluviatilis_ and die Bedeutung der Amöbocyten für die Spongilliden,"
Arch. Naturg. Berlin, lxxiii (i), pp. 273-286.

1907. ANNANDALE, "The buds of _Spongilla proliferens_, Annand.," Rec.
Ind. Mus. i, pp. 267, 268.

1907. ANNANDALE, "Embryos of _Ephydatia blembingia_, Evans," _ibid._ p.
269.

1907. ANNANDALE, "The nature of the pores in _Spongilla_," _ibid._ pp.
270-271.

(c) _Descriptions of Asiatic Species[V] and of Animals associated with
them._

     [Footnote V: Descriptions of Siberian sponges are not
     included in these references.]

1847-1848. CARTER, "Notes on the species, structure, and animality of
the Freshwater Sponges in the tanks of Bombay (Genus _Spongilla_),"
Trans. Bombay Med. & Phys. Soc., 1847, and Ann. Nat. Hist. (2) i, pp.
303-311, 1848.

1849. CARTER, "A descriptive account of the Freshwater Sponges (Genus
_Spongilla_) in the Island of Bombay, with observations on their
structure and development," Ann. Nat. Hist. (2) iv, pp. 81-100, pls.
iii-v.

1868. MARTENS, E. VON, "Ueber einige östasiatische Süsswasserthiere,"
Arch. Naturg. Berlin, xxxiv, pp. 1-67: IV., Ein Süsswasserschwamm aus
Borneo, pp. 61-64, pl. i, fig. 1.

1881. CARTER, "On _Spongilla cinerea_," Ann. Nat. Hist. (5) vii, p. 263.

1890. WEBER, M., "Zoologische Ergebnisse einer Reise in Niederländisch
Ost-Indien," i, pp. 30-47, pl. iv.

1901. EVANS, R., "A description of _Ephydatia blembingia_, with an
account of the formation and structure of the gemmule," Q. J. Micr. Sci.
xliv, pp. 71-109, pls. i-iv.

1901. WELTNER, "Süsswasserspongien von Celebes (Spongillidenstudien,
IV.)," Arch. Naturg. Berlin, lxvii (1) (Special Number), pp. 187-204,
pls. vi, vii.

1906. ANNANDALE, "A variety of _Spongilla lacustris_ from brackish water
in Bengal," J. As. Soc. Bengal, (n. s.) ii, pp. 55-58.

1906. ANNANDALE, "Some animals found associated with _Spongilla carteri_
in Calcutta," _ibid._ pp. 187-196.

1907. WILLEY, "Freshwater Sponge and Hydra in Ceylon," Spolia Zeylanica,
iv, pp. 184-185.

1907. ANNANDALE, "On Freshwater Sponges from Calcutta and the
Himalayas," J. As. Soc. Bengal, (n. s.) iii, pp. 15-26.

1907. ANNANDALE, "Gemmules of _Trochospongilla phillottiana_, Annand.,"
Rec. Ind. Mus. i, p. 269.

1907. ANNANDALE, "Description of two new Freshwater Sponges from Eastern
Bengal, with remarks on allied forms," _ibid._ pp. 387-392.

1908. ANNANDALE, "Preliminary notice of a collection of Sponges from W.
India, with descriptions of two new species," Rec. Ind. Mus. ii, pp.
25-28.

1908. KIRKPATRICK, "Description of a new variety of _Spongilla
loricata_, Weltner," _ibid._ pp. 97-99.

1908. ANNANDALE, "Preliminary notice of a collection of Sponges from
Burma, with the description of a new species of _Tubella_," _ibid._ pp.
157-158.

1909. ANNANDALE, "Report on a small collection of Sponges from
Travancore," Rec. Ind. Mus. iii, pp. 101-104, pl. xii.

1909. NEEDHAM, "Notes on the Neuroptera in the collection of the Indian
Museum," _ibid._ pp. 206-207.

1909. ANNANDALE, "Description of a new species of _Spongilla_ from
Orissa," _ibid._ p. 275.

1909. ANNANDALE, "Beiträge zur Kenntnis der Fauna von Süd-Afrika: IX.
Freshwater Sponges," Zool. Jahrb. (Syst.) xxvii, pp. 559-568.

1909. ANNANDALE, "Report on a collection of Freshwater Sponges from
Japan," Annot. Zool. Japon, vii, pp. 105-112, pl. ii.

1909. ANNANDALE, "Freshwater Sponges in the collection of the United
States National Museum: Part I. Specimens from the Philippines and
Australia," P. U.S. Mus. xxxvi, pp. 627-632.

1909. ANNANDALE, "Freshwater Sponges collected in the Philippines by the
'Albatross' Expedition," _ibid._ xxxvii, pp. 131-132.

1909. ANNANDALE, "Freshwater Sponges in the collection of the United
States National Museum: Part II. Specimens from North and South
America," _ibid._ pp. 401-406.

1910. ANNANDALE, "Freshwater Sponges in the collection of the United
States National Museum: Part III. Description of a new species of
_Spongilla_ from China," _ibid._ xxxviii, p. 183.

1910. ANNANDALE, "Description of a new species of Sponge from Cape
Comorin," Rec. Ind. Mus. v, p. 31.

1910. STEPHENSON, "On some aquatic Oligochæte worms commensal in
_Spongilla carteri_," _ibid._ pp. 233-240.

1910. ANNANDALE, "Note on a Freshwater Sponge and Polyzoon from Ceylon,"
Spolia Zeylanica, vii. p. 63, pl. i.




GLOSSARY OF TECHNICAL TERMS USED IN PART I.


  _Amphioxi_ (adj.               Rod-like spicules sharp at both ends.
  _amphioxous_)

  _Amphistrongyli_ (adj.         Rod-like spicules blunt at both ends.
  _amphistrongylous_)

  _Basal membrane_               A horny, structureless membrane found
                                 at the base of some sponges.

  _Birotulate_ (subst. or adj.)  Spicule with a transverse disk at both
                                 ends.

  _Bubble-cells_                 Spherical cells of the parenchyma the
                                 contents of which consist of a drop of
                                 liquid covered by a thin film of
                                 protoplasm.

  _Ciliated_ (or _flagellated_)  A cavity lined with collar-cells.
  _chamber_

  _Collar-cell_ (_choanocyte_)   Cell provided at one end with a
                                 membranous collar and a vibratile lash
                                 or flagellum that springs from within
                                 the collar.

  _Derma_ or _ectodermal layer_  A layer of flat cells arranged like a
                                 pavement on the surface of the sponge.

  _Exhalent_ (or _efferent_)     A tubular canal through which water
  _canal_                        passes from a ciliated chamber towards
                                 the osculum.

  _Fibres_ (skeleton)            Thread-like structures that compose the
                                 skeleton of the sponge and are formed
                                 (in the Spongillidæ) mainly of
                                 overlapping spicules.

  _Flesh-spicules_               Microscleres (_q. v._) that lie free in
                                 the parenchyma and the derma.

  _Foramen_                      An orifice of the gemmule.

  _Foraminal tubule_             A horny tube that surrounds the foramina
                                 of some gemmules.

  _Gemmule_                      A mass of cells packed with food-material,
                                 surrounded by at least one horny coat,
                                 capable of retaining vitality in
                                 unfavourable conditions and finally of
                                 giving origin to a new sponge.

  _Green corpuscles_             Minute green bodies found inside cells
                                 of sponges and other animals and
                                 representing a stage in the life-history
                                 of an alga (_Chlorella_).

  _Inhalent_ (or _afferent_)     A tubular canal through which water
  canal                          passes from the exterior towards a
                                 ciliated chamber.

  _Megascleres_                  The larger spicules that (in the
                                 Spongillidæ) form the basis of the
                                 skeleton of the sponge.

  _Microscleres_                 Smaller spicules that lie free in the
                                 substance or the derma of the sponge, or
                                 are associated with the gemmule.

  _Monaxon_                      (Of spicules) having a single main axis;
                                 (of sponges) possessing skeleton spicules
                                 of this type.

  _Osculum_                      An aperture through which water is
                                 ejected from the sponge.

  _Oscular collar_               A ring-shaped membrane formed by an
                                 extension of the derma round an osculum.

  _Parenchyma_                   The gelatinous part of the sponge.

  _Pavement layer_               Adherent gemmules arranged close together
                                 in a single layer at the base of a sponge.

  _Pneumatic coat_               A horny or chitinous layer on the surface
                                 of the gemmule containing air-spaces.
                                 If these spaces are of regular form and
                                 arrangement it is said to be _cellular_;
                                 if they are minute and irregular it is
                                 called _granular_.

  _Pore_                         A minute hole through which water is
                                 taken into the sponge.

  _Pore-cell_ (_porocyte_)       A cell pierced by a pore.

  _Radiating fibres_             Fibres in the skeleton of a sponge that
                                 are vertical or radiate from its centre.

  _Rotula_                       A transverse disk borne by a microsclere.

  _Rotulate_ (subst. or adj.)    Spicule bearing one or two transverse
                                 disks.

  _Spicule_                      A minute mineral body of regular and
                                 definite shape due not to the forces of
                                 crystallization but to the activity of
                                 the living cell or cells in which it is
                                 formed.

  _Spongin_                      The horny substance found in the skeletal
                                 framework and the coverings of gemmules
                                 of sponges. Structures formed of
                                 this substance are often referred to as
                                 _chitinous_.

  _Subdermal cavity_             A cavity immediately below the derma
                                 (_q. v._).

  _Transverse fibres_            Fibres in the skeleton of a sponge that
                                 run across between the radiating fibres.

  _Tubelliform_ (of spicule)     Having a straight shaft with a transverse
                                 disk at one end and a comparatively
                                 small knob-like projection at the other.




SYSTEMATIC LIST OF THE INDIAN SPONGILLIDÆ.


[Types, schizotypes, or cotypes have been examined in the case of all
species, &c., whose names are marked thus, *.]

  Genus 1. SPONGILLA, Lamarck (1816).
    Subgenus A. EUSPONGILLA, Vejdovsky (1883).
       1.     ? _S. lacustris_, auct. (perhaps in N.W. India).
       1_a_. _S. lacustris_ subsp. _reticulata_*, Annandale (1907).
       2.    _S. proliferens_*, Annandale (1907).
       3.    _S. alba_*, Carter (1849).
       3_a_. _S. alba_ var. _cerebellata_, Bowerbank (1863).
       3_b_. _S. alba_ var. _bengalensis_*, Annandale (1906).
       4.    _S. cinerea_*, Carter (1849).
       5.    _S. travancorica_*, Annandale (1909).
       6.    _S. hemephydatia_*, Annandale (1909).
       7.    _S. crateriformis_* (Potts) (1882).
    Subgenus B. EUNAPIUS, J. E. Gray (1867).
       8_a_. _S. carteri_ var. _mollis_*, nov.
       8_b_. _S. carteri_ var. _cava_*, nov.
       8_c_. _S. carteri_ var. _lobosa_*, nov.
       9_a_. _S. fragilis_ subsp. _calcuttana_*, nov.
       9_b_. _S. fragilis_ var. _decipiens_, Weber (probably Malaysian,
              not Indian).
      10.    _S. gemina_*, sp. nov.
      11.    _S. crassissima_*, Annandale (1907).
      11_a_. _S. crassissima_ var. _crassior_*, Annandale (1907).
    Subgenus C. STRATOSPONGILLA, Annandale (1909).
      12.    _S. indica_*, Annandale (1908).
      13.    _S. bombayensis_*, Carter (1882).
      14.    _S. ultima_*, Annandale (1910).

  Genus 2. PECTISPONGILLA, Annandale (1909).
      15.    _P. aurea_*, Annandale (1909).
      15_a_. _P. aurea_ var. _subspinosa_*, nov.

  Genus 3. EPHYDATIA, Lamouroux (1816).
      16.    _E. meyeni_* (Carter) (1849).

  Genus 4. DOSILIA, J. E. Gray (1867).
      17.    _D. plumosa_* (Carter) (1849).

  Genus 5. TROCHOSPONGILLA, Vejdovsky (1883).
      18.    _T. latouchiana_*, Annandale (1907).
      19.    _T. phillottiana_*, Annandale (1907).
      20.    _T. pennsylvanica_* (Potts) (1882).

  Genus 6. TUBELLA, Carter (1881).
      21.    _T. vesparioides_*, Annandale (1908).

  Genus 7. CORVOSPONGILLA, nov.
      22.    _C. burmanica_* (Kirkpatrick) (1908).
      23.    _C. lapidosa_* (Annandale) (1908).


Order HALICHONDRINA.


Siliceous monaxon sponges in which the horny skeleton is much reduced or
absent and the spicular skeleton is more or less definitely reticulate.
The microscleres are usually rod-like and rarely have more than one main
axis.


Family SPONGILLIDÆ.

SPONGILLADÆ, J. E. Gray, P. Zool. Soc. London, 1867, p. 550.

Freshwater Halichondrina which at certain seasons produce gemmules armed
with peculiar microscleres. Two distinct kinds of microsclere are often
present, that associated with the gemmule sometimes consisting of a
vertical shaft at the ends of which transverse disks or rotulæ are
borne. There is always at least a trace of a subdermal cavity.

Many authors divide the Spongillidæ into two subfamilies:--Spongillinæ
(or Euspongillinæ), in which the gemmule-spicules have no transverse
rotulæ, and Meyeninæ (or Ephydatiinæ), in which they have rotules at one
or both ends. So gradual, however, is the transition that I find it
difficult to decide in one instance to which of two genera, typical
respectively of the two "subfamilies," a species should be assigned.
Minchin in his account of the Porifera in Lankester's "Treatise on
Zoology" (1900) regards the Spongillidæ merely as a subfamily of the
Heterorrhaphidæ, and there certainly are few differences of a definite
nature between them and the marine family (or subfamily) Remeridæ.


  _Key to the Indian Genera of_ Spongillidæ.

    I. Microscleres without transverse disks.
       A. Microscleres of the parenchyma similar
          in general structure to those or the
          gemmule; the latter without comb-like
          vertical rows of spines at the ends           SPONGILLA, p. 67.
       B. Microscleres of the gemmule with comb-like
          vertical rows of spines at both ends    PECTISPONGILLA, p. 106.

   II. Some or all of the microscleres birotulate.
       (Birotulate microscleres of one kind only.)
       A. Microscleres of the gemmule birotulate, the
          rotules with serrated or strongly sinuous
          edges; parenchyma spicules usually absent,
          never of complicated structure               EPHYDATIA, p. 108.
       B. Microscleres of the gemmule as in
          _Ephydatia_; microscleres of the parenchyma
          consisting of numerous shafts
          meeting in different planes in a central
          nodule                                         DOSILIA, p. 110.
       C. Microscleres as in _Ephydatia_ except
          that the rotulæ of the gemmule-spicules
          have smooth edges                      TROCHOSPONGILLA, p. 113.
       D. Microscleres of the gemmule without a
          trace of rotules, those of the parenchyma
          birotulate                        CORVOSPONGILLA, nov., p. 122.

  III. Microscleres of the gemmule with a well-developed
       basal rotule and a vertical shaft
       ending above in a mere knob.                      TUBELLA, p. 120.

The most distinct genus of Spongillidæ not yet found in India is
_Heteromeyenia_, Potts. It is easily distinguished from all others by
the fact that the birotulate spicules of the gemmule are of two quite
distinct kinds, which occur together on every mature gemmule.
_Heteromeyenia_ is represented by several American species, one of which
has been found in Europe. _Acalle_, J. E. Gray, which is represented by
a single South American species (_Spongilla recurvata_, Bowerbank), is
related to _Heteromeyenia_ but has one kind of gemmule-spicule
tubelliform, the other birotulate. Probably _Uraguaya_, Carter, should
be regarded as a subgenus of _Trochospongilla_ with an unusually solid
skeleton; it is peculiar to S. America. _Parmula_, Carter (=_Drulia_,
Gray) includes South American forms allied to _Tubella_, but with the
shaft of the gemmule-spicule degenerate and consisting of a mere
projection in the centre of a shield-like body, which represents the
lower rotule. The status of _Potamolepis_, Marshall, originally
described from the Lake of Galilee, is very doubtful; possibly some or
all of its species belong to the subgenus of _Spongilla_ here called
_Stratospongilla_ (p. 100); but they are stated never to produce
gemmules. The same is the case as regards _Pachydictyum_, Weltner, which
consists of a single species from Celebes.

The sponges from Lake Baikal assigned by Weltner (Arch. Naturg. lxi (i)
p. 131) to the subfamily Lubomirskinæ are of doubtful position and need
not be considered here; while _Lessepsia_, Keller, from one of the salt
lakes on the Suez Canal, certainly does not belong to the family,
although it is assigned to it by von Lendenfeld (Mon. Horny Sponges, p.
904 (1889)) and subsequently by Minchin (Porifera, p. 152, in
Lankester's Treatise on Zoology, part ii (1900)).


Genus 1. SPONGILLA, _Lamarck_ (Carter _emend._).

    _Spongilla_, Lamarck, Histoire des Animaux sans Vertèbres, ii, p. 111
      (1836).
    _Spongilla_, Carter, Ann. Nat. Hist. (5) vii, p. 86 (1881).
    _Euspongilla_, Vejdovsky, Abh. Böhm. Ges. xii, p. 15 (1883).
    _Spongilla_, Potts, P. Ac. Philad. 1887, p. 182.

TYPE, _Spongilla lacustris_, auctorum.

Spongillidæ in which the gemmules have (normally) cylindrical or
subcylindrical spicules that are sharp or blunt at the ends, without a
distinct transverse disk or disks and without comb-like vertical rows of
spines.

The skeleton is variable in structure, sometimes being almost amorphous,
sometimes having well-defined radiating and transverse fibres firmly
compacted with spongin. The skeleton-spicules are either sharp or blunt
at the ends. Flesh-spicules are often absent; when present they are
needle-like and resemble the gemmule-spicules in general structure; they
have not even rudimentary rotules at their ends. The gemmules either lie
free in the substance of the sponge or are attached to its support;
sometimes they adhere together in free or attached groups.

_Spongilla_ is undoubtedly the most primitive genus of the Spongillidæ,
its spicules showing less sign of specialization than those of any other
genus included in the family. As a fossil it goes back at any rate to
the Upper Jurassic (p. 52).

GEOGRAPHICAL DISTRIBUTION.--Cosmopolitan. In most countries the majority
of the freshwater sponges belong to this genus, but in Japan _Ephydatia_
seems to predominate.


_Key to the Indian Species of_ Spongilla.

  I. Gemmule provided with a thick, apparently
      granular pneumatic coat in
      which the gemmule-spicules are arranged
      tangentially or vertically. (Subgenus
      _Euspongilla_, p. 69.)
    A. No foraminal tubule.
      _a._  Sponge bright green, soft and
            compressiblewhen fresh, very fragile
            dry                                    _lacustris_, p. 69.
      _a'._ Sponge white or grey, hard both
            fresh and dry                          _alba_, p. 76.
    B. A foraminal tubule present.
      _b._  Skeleton-spicules smooth.
        beta.   Gemmules free; gemmule-spicules
                arranged tangentially and
                horizontally                       _proliferens_, p. 72.
        beta'.  Gemmules free; gemmule-spicules
                arranged vertically or nearly
                so in a single series              _hemephydatia_, p. 82.
        beta''. Gemmules firmly fixed
                to the support of the sponge;
                gemmule-spicules almost vertical,
                irregularly arranged, as a rule in
                more than one series               _travancorica_, p. 81.
      _b'._ Skeleton-spicules spiny or
            irregular in outline.
        beta'''. Gemmule-spicules tangential
                 and horizontal, without
                 rudimentary rotules               _cinerea_, p. 79.
        beta''''. Gemmule-spicules vertical or
                 nearly so, often with
                 rudimentary rotules at the tips   _crateriformis_, p. 83.

  II. Gemmules surrounded in several layers
      by distinct polygonal air-spaces with
      chitinous walls. (Subgenus _Eunapius_,
      p. 86.)
    A. Gemmules single. Skeleton- and
       gemmule-spicules smooth, pointed,
       not very stout                              _carteri_, p. 87.
    B. Gemmules bound together in pairs.
       Skeleton friable; skeleton-spicules
       slender                                     _gemina_, nov., p. 97.
    C. Gemmules bound together in free
       groups of more than two or forming
       a "pavement-layer" at the base of
       the sponge.
      _c._  Skeleton friable;
            skeleton-spicules slender              _fragilis_, p. 95.
      _c'._ Skeleton very hard and
            resistant; skeleton-spicules stout     _crassissima_, p. 98.

  III. Gemmules without or with irregular
       pneumatic coat, covered by a chitinous
       membrane or membranes in which the
       gemmule-spicules lie parallel to the
       surface. (Subgenus _Stratospongilla_,
       p. 100.)

    A. Skeleton spicules spiny or irregular in
       outline.

      _a._  Skeleton-spicules blunt; gemmules
            covered by a single chitinous
            membrane                               _indica_, p. 100.

      _a'._ Skeleton-spicules sharp; gemmules
            covered by two chitinous membranes     _bombayensis_, p. 102.

    B. Skeleton-spicules smooth.
       Skeleton-spicules sharp; gemmule
       spicules very irregular in form             _ultima_, p. 104.


Subgenus A. EUSPONGILLA, _Vejdovsky_.

    _Euspongilla_, Vejdovsky, Abh. Böhm. Ges. xii, p. 15 (1883).
    _Euspongilla_, _id._, in Potts's "Fresh-Water Sponges," P. Ac. Philad.
      1887, p. 172.
    _Euspongilla_, Weltner, in Zacharias's Tier- und Pflanzenwelt des
      Süsswassers, i, p. 210 (1891).

TYPE, _Spongilla lacustris_, auctorum.

Spongillæ in which the gemmules are covered with a thick, apparently
granular pneumatic coat. A delicate membrane often occurs outside this
coat, but it is never thick or horny. The gemmules usually lie free in
the sponge but sometimes adhere to its support; rarely they are fastened
together in groups (_e. g._ in _S. aspinosa_, Potts). The
skeleton-spicules are never very stout and the skeleton is always
delicate.

The species in this subgenus are closely allied and must be
distinguished rather by the sum of their peculiarities than by any one
character. They occur in all countries in which Spongillidæ are found.
Seven Indian species may be recognized.


1. Spongilla lacustris, _auctorum_.

    _Spongilla lacustris_, Bowerbank, P. Zool. Soc. London, 1863, p. 441,
      pl. xxxviii, fig. 14.
    _Spongilla lacustris_, Carter, Ann. Nat. Hist. (5) vii, p. 87 (1881).
    _Euspongilla lacustris_, Vejdovsky, in Potts's "Fresh-Water Sponges,"
      P. Ac. Philad. 1887, p. 172.
    _Spongilla lacustris_, Potts, _ibid._, p. 186, pl. v, fig. 1, pl. vii,
      figs. 1-6.
    _Euspongilla lacustris_, Weltner, in Zacharias's Tier- und Pflanzenwelt
      des Süsswassers, i, p. 211, figs. 36-38 (1891).
    _Spongilla lacustris_, _id._, Arch. Naturg. lxi (i), pp. 118, 133-135
      (1895).
    _Spongilla lacustris_, Annandale, J. Linn. Soc., Zool., xxx, p. 245
      (1908).

     [I have not attempted to give a detailed synonymy of this
     common species. There is no means of telling whether many of
     the earlier names given to forms or allies of _S. lacustris_
     are actual synonyms, and it would serve no useful purpose,
     so far as the fauna of India is concerned, to complicate
     matters by referring to obscure descriptions or possible
     descriptions of a species only represented in India, so far
     as we know, by a specialized local race, to which separate
     references are given.]

_Sponge_ soft and easily compressed, very brittle when dry, usually
consisting of a flat or rounded basal portion of no great depth and of
long free cylindrical branches, which droop when removed from the water;
branches occasionally absent. Colour bright green when the sponge is
growing in a strong light, dirty flesh-colour when it is growing in the
shade. (Even in the latter case traces of the "green corpuscles" can be
detected in the cells of the parenchyma.) Oscula star-shaped, of
moderate size, as a rule rendered conspicuous by the furrows that
radiate from them over the outer surface of the parenchyma below the
external membrane; oscular collars well developed.

_Skeleton_ reticulate, loose, with definite radiating and transverse
fibres held together by a small quantity of spongin; the fibres slender
but not extremely so.

_Spicules._ Skeleton-spicules smooth, sharply pointed, long, slender.
Flesh-spicules slender, covered with small spines, sharply pointed,
nearly straight. Gemmule-spicules resembling the flesh-spicules but
shorter and as a rule more strongly curved, sometimes bent so as to form
semicircular figures, usually pointed somewhat abruptly; their spines
relatively longer than those of the flesh-spicules, often curved
backwards, especially near the ends of the spicules, at which points
they are often longer than elsewhere.

_Gemmules_ usually numerous in autumn, lying free in the sponge,
spherical, variable in size but usually rather large, as a rule covered
with a thick granular coat in which the spicules are arranged
tangentially; a horizontal layer of spicules often present in the
external membrane; the granular coat and its spicules occasionally
deficient. No foraminal tubule; its place sometimes taken by an open,
bowl-shaped chitinous structure the base of which is in continuity with
the inner chitinous coat of the gemmule.

_S. lacustris_ is an extremely variable species, varying in the size,
proportions and shape of its spicules, in its external form and in the
size and structure of the gemmule. A considerable number of varieties
have been described from different parts of Europe and N. America, but
some of these may represent distinct but closely-allied species;
descriptions of most of them will be found in Potts's "Fresh-Water
Sponges." The embryology and the earlier stages of the development from
the egg have been described in great detail by Evans (Quart. J. Micr.
Sci. (n. s.) xlii, p. 363 (1899)), while the anatomy and physiology are
discussed by most authors who have written on these features in the
Spongillidæ.

TYPE.--It is impossible to say who was the first authority to use the
name _Spongilla lacustris_ in the sense in which it is used by recent
authors. No type can therefore be recognized.

GEOGRAPHICAL DISTRIBUTION.--_S. lacustris_ occurs all over Europe and N.
America and is probably the commonest species in most parts of both
continents. It has also been found in Northern Asia and may occur in the
Himalayan lakes and in the north-west of India.


1 _a._ Subspecies reticulata*, _Annandale_.

     _Spongilla reticulata_, Annandale, Rec. Ind. Mus. i, p. 387,
     pl. xiv, fig. 1 (1907).

     _Spongilla lacustris_ subspecies _reticulata_, _id._, P.
     U.S. Mus. xxxvii, p. 401 (1909).

This race differs from the typical _S. lacustris_ in the following
particulars:--

     (1) The branches are always compressed and anastomose
     freely when well developed (fig. 5, p. 37);

     (2) the skeleton-fibres are finer;

     (3) the skeleton-spicules are longer;

     (4) the gemmule-spicules are longer and more slender and are
     never strongly bent.

[Illustration: Fig. 8.

A=gemmule-spicules of _Spongilla lacustris_ subsp. _reticulata_ (from
type); B=gemmule-spicules of _S. alba_ from Calcutta: both highly
magnified.]

As regards the form of the skeleton- and gemmule-spicules and also that
of the branches the subspecies _reticulata_ resembles _S. alba_ rather
than _S. lacustris_, but owing to the fact that it agrees with _S.
lacustris_ in its profuse production of branches, in possessing green
corpuscles and in its fragility, I think it should be associated with
that species.

The branches are sometimes broad (fig. 5, p. 37), sometimes very
slender. In the latter condition they resemble blades of grass growing
in the water.

TYPE in the Indian Museum; a co-type in the British Museum.

GEOGRAPHICAL DISTRIBUTION.--All over Eastern India and Burma; also in
the Bombay Presidency. _Localities:_--BENGAL, Port Canning, Ganges
delta; Rajshahi (Rampur Bhulia) on the Ganges, 150 miles N. of Calcutta
(_Annandale_); Puri district, Orissa (_Annandale_); R. Jharai, Siripur,
Saran district, Tirhut (_M. Mackenzie_): MADRAS PRESIDENCY, Madras
(town) (_J. R. Henderson_): BOMBAY PRESIDENCY, Igatpuri, W. Ghats
(_Annandale_).

BIOLOGY.--This subspecies is usually found in small masses of water,
especially in pools of rain-water, but Mr. Mackenzie found it growing
luxuriantly in the Jharai at a time of flood in September. It is very
abundant in small pools among the sand-dunes that skirt the greater part
of the east coast of India. Here it grows with great rapidity during the
"rains," and often becomes desiccated even more rapidly as soon as the
rain ceases. As early in the autumn as October I have seen masses of the
sponge attached, perfectly dry, to grass growing in the sand near the
Sur Lake in Orissa. They were, of course, dead but preserved a life-like
appearance. Some of them measured about six inches in diameter. At Port
Canning the sponge grows during the rains on the brickwork of bridges
over ditches of brackish water that dry up at the beginning of winter,
while at Rajshahi and at Igatpuri I found it at the edges of small
ponds, at the latter place in November, at the former in February.
Specimens taken at Madras by Dr. Henderson during the rains in small
ponds in the sand contained no gemmules, but these structures are very
numerous in sponges examined in autumn or winter.

Numerous larvæ of _Sisyra indica_ (p. 92) were found in this sponge at
Rajshahi. Unlike those obtained from _S. alba_, they had a green colour
owing to the green matter sucked from the sponge in their stomachs. The
_coralloides_ phase of _Plumatella fruticosa_ (p. 219) was also found in
_S. lacustris_ subsp. _reticulata_ at Rajshahi.

So far as my experience goes, this subspecies has always a bright green
colour due to the presence of "green corpuscles," even when it is
growing in a pond heavily shaded by trees or under the arch of a small
bridge. Probably the more intense light of India enables the corpuscles
to flourish in situations in which in Europe they would lose their
chlorophyll.


2. Spongilla proliferens*, _Annandale_.

     _Spongilla cinerea_, Weber (_nec_ Carter), Zool. Ergeb.
     Niederl. Ost-Ind. vol. i, pp. 35, 46 (1890).

     _Spongilla proliferens_, Annandale, J. Asiat. Soc. Bengal,
     1907, p. 15, fig. 1.

     _Spongilla proliferens_, _id._, Rec. Ind. Mus. i, pp. 267,
     271 (1907).

_Sponge_ forming soft, shallow cushions rarely more than 10 cm. in
diameter on the leaves of water-plants, or small irregular masses on
their roots and stems. Colour bright green. Oscula moderate, flat,
surrounded by deep, cone-shaped collars; radiating furrows and canals in
the parenchyma surrounding them often deep. External pores contained
normally in single cells. The surface frequently covered by small
rounded buds; true branches if present more or less flattened or
conical, always short, as a rule absent.

_Skeleton_ loose, feebly reticulate at the base of the sponge;
transverse fibres slender in the upper part of the sponge, often
scarcely recognizable at its base. Very little spongin present.

_Spicules._ Skeleton-spicules long, smooth, sharply pointed; the length
on an average at least 20 times the greatest breadth, often more.
Flesh-spicules slender, gradually pointed, nearly straight, covered with
minute straight or nearly straight spines. Gemmule-spicules very
similar, but usually a little stouter and often blunt at the ends; their
spines rather longer than those on the flesh-spicules, usually more
numerous near the ends than in the middle of the spicule, slightly
retroverted, those at the extreme tips often so arranged as to suggest a
rudimentary rotule.

[Illustration: Fig. 9.--Gemmule of _Spongilla proliferens_ as seen in
optical section (from Calcutta), × 140.]

_Gemmules_ usually numerous, lying free near the base of the sponge,
very variable in size, spherical, surrounded by a thick granular layer
in which the spicules, which are always very numerous, are arranged
tangentially, their position being more near the vertical than the
horizontal; a few horizontal spicules usually present on the external
surface of the gemmule, which frequently has a ragged appearance owing
to some of the tangential spicules protruding further than others.
Foraminal tubule stout, cylindrical, usually somewhat contorted; its
orifice irregular in outline. Sometimes more than one foramen present.

_S. proliferens_ can be distinguished from all forms of _S. lacustris_
and _S. alba_ by the fact that its gemmules possess a foraminal tubule;
from _S. cinerea_ it can be distinguished by its colour and its smooth
skeleton-spicules, and from _S. travancorica_ by its free gemmules. I
have been enabled by the kindness of Prof. Max Weber to examine
specimens from Celebes and Java identified by him as _S. cinerea_,
Carter, and have no doubt that they belong to my species.

TYPE in the Indian Museum; a co-type in the British Museum.

GEOGRAPHICAL DISTRIBUTION.--All over Eastern India and Burma; also in
Cochin on the west coast; Ceylon; W. China; Java, Flores and Celebes.
_Localities_:--BENGAL, Calcutta and neighbourhood (_Annandale_);
Berhampore, Murshidabad district (_R. E. Lloyd_): ASSAM, Mangal-dai near
the Bhutan frontier (_S. W. Kemp_): MADRAS PRESIDENCY, Madras (town) and
neighbourhood (_J. R. Henderson_); Rambha, Ganjam district
(_Annandale_); Bangalore, Mysore (alt. _ca._ 3000 ft.) (_Annandale_);
Ernakulam and Trichur, Cochin (_G. Mathai_): BURMA, Rangoon
(_Annandale_, _J. Coggin Brown_); Prome, Upper Burma (_J. Coggin
Brown_); Kawkareik, Amherst district, Tenasserim (_Annandale_): CEYLON,
between Maradankawela and Galapita-Gala, North Central Province
(_Willey_). Mr. J. Coggin Brown has recently brought back specimens from
Yunnan.

BIOLOGY.--_S. proliferens_ is usually found in ponds which never dry up;
Prof. Max Weber found it in small streams in Malaysia. It is common in
India on the leaves of _Vallisneria_ and _Limnanthemum_, on the roots of
_Pistia stratiotes_ and on the stems of rushes and grass. So far as I
have been able to discover, the life of the individual sponge is short,
only lasting a few weeks.

Sexual reproduction occurs seldom or never, but reproduction by means of
buds and gemmules continues throughout the year. The former is a rare
method of reproduction in most Spongillidæ but in this species occurs
normally and constantly, the buds being often very numerous on the
external surface. They arise a short distance below the surface as
thickenings in the strands of cells that accompany the radiating fibres
of the skeleton. As they grow they push their way up the fibres, forcing
the external membrane outwards. The membrane contracts gradually round
their bases, cuts off communication between them and the parent sponge
and finally sets them adrift. No hole remains when this takes place, for
the membrane closes up both round the base of the bud and over the
aperture whence it has emerged.

The newly liberated bud already possesses numerous minute pores, but as
yet no osculum; its shape exhibits considerable variation, but the end
that was farthest from the parent-sponge before liberation is always
more or less rounded, while the other end is flat. The size also varies
considerably. Some of the buds float, others sink. Those that float do
so either owing to their shape, which depends on the degree of
development they have reached before liberation, or to the fact that a
bubble of gas is produced in their interior. The latter phenomenon only
occurs when the sun is shining on the sponge at the moment they are set
free, and is due to the action of the chlorophyll of the green bodies so
abundant in certain of the parenchyma cells of this species. If the
liberation of the bud is delayed rather longer than usual, numbers of
flesh-spicules are produced towards the ends of the primary
skeleton-fibres and spread out in one plane so as to have a fan-like
outline; in such buds the form is more flattened and the distal end less
rounded than in others, and the superficial area is relatively great, so
that they float more readily. Those buds that sink usually fall in such
a way that their proximal, flattened end comes in contact with the
bottom or some suspended object, to which it adheres. Sometimes,
however, owing to irregularity of outline in the distal end, the
proximal end is uppermost. In this case it is the distal end that
adheres. Whichever end is uppermost, it is in the uppermost end, or as
it may now be called, the upper surface, that the osculum is formed.
Water is drawn into the young sponge through the pores and, finding no
outlet, accumulates under the external membrane, the subdermal cavity
being at this stage even larger than it is in the adult sponge.
Immediately after adhesion the young sponge flattens itself out. This
process apparently presses together the water in the subdermal cavity
and causes a large part of it to accumulate at one point, which is
usually situated near the centre of the upper surface. A transparent
conical projection formed of the external membrane arises at this point,
and at the tip of the cone a white spot appears. What is the exact cause
of this spot I have not yet been able to ascertain, but it marks the
point at which the imprisoned water breaks through the expanded
membrane, thus forming the first osculum. Before the aperture is formed,
it is already possible to distinguish on the surface of the parenchyma
numerous channels radiating from the point at which the osculum will be
formed to the periphery of the young sponge. These channels as a rule
persist in the adult organism and result from the fact that the inhalent
apertures are situated at the periphery, being absent from both the
proximal and the distal ends of the bud. In the case of floating buds
the course of development is the same, except that the osculum, as in
the case of development from the gemmule in other species (see Zykoff,
Biol. Centrbl. xii, p. 713, 1892), is usually formed before adhesion
takes place.

The sponge of _S. proliferens_ is usually too small to afford shelter to
other animals, and I have not found in it any of those commonly
associated with _S. carteri_ and _S. alba_.

Owing to its small size _S. proliferens_ is more easily kept alive in an
aquarium than most species, and its production of buds can be studied in
captivity. In captivity a curious phenomenon is manifested, viz. the
production of extra oscula, often in large numbers. This is due either
to a feebleness in the currents of the sponge which makes it difficult
to get rid of waste substances or to the fact that the canals get
blocked. The effluent water collects in patches under the external
membrane instead of making its way out of the existing oscula, and new
oscula are formed over these patches in much the same way as the first
osculum is formed in the bud.


3. Spongilla alba*, _Carter_.

     _Spongilla alba_, Carter, J. Bombay Asiat. Soc. iii, p. 32,
     pl. i, fig. 4 & Ann. Nat. Hist. (2) iv, p. 83, pl. iii, fig.
     4 (1849)

     _Spongilla alba_, Bowerbank, P. Zool. Soc. London, 1863, p.
     463 pl. xxxviii, fig. 15.

     _Spongilla alba_, Carter, Ann. Nat. Hist. (5) vii, p. 88
     (1881).

     _Spongilla alba_, Petr, Rozp. Ceske Ak. Praze, Trída, ii,
     pl. i, figs. 3-6 (1899) (text in Czech).

     _Spongilla alba_, Annandale, Rec. Ind. Mus. i, p. 388, pl.
     xiv, fig. 2 (1907).

_Sponge_ forming masses of considerable area, but never of more than
moderate depth or thickness. Surface smooth and undulating or with
irregular or conical projections; sponge hard but brittle; colour white
or whitish; oscula of moderate or large size, never very conspicuous;
radiating furrows absent or very short; external membrane adhering to
the substance of the sponge.

_Skeleton_ forming a moderately dense network of slender radiating and
transverse fibres feebly held together; little spongin present; the
meshes much smaller than in _S. lacustris_ or _S. proliferens_.

_Spicules._ Skeleton-spicules smooth, sharply pointed, slender, feebly
curved. Gemmule-spicules (fig. 8, p. 71) slender, cylindrical, blunt or
abruptly pointed at the ends, feebly curved, bearing relatively long
backwardly directed spines, which are usually more numerous at the ends
than near the middle of the shaft. Flesh-spicules very numerous in the
parenchyma and especially the external membrane, as a rule considerably
more slender and more sharply pointed than the gemmule-spicules, covered
with straight spines which are often longer at the middle of the shaft
than at the ends.

_Gemmules_ usually of large size, with a moderately thick granular
layer; spicules never very numerous, often lying horizontally on the
external surface of the gemmule as well as tangentially in the granular
layer; no foraminal tubule; a foraminal cup sometimes present.


3_a_. Var. cerebellata, _Bowerbank_.

     _Spongilla cerebellata_, Bowerbank, P. Zool. Soc. London,
     1863, p. 465, pl. xxxviii, fig. 16.

     _Spongilla alba_ var. _cerebellata_, Carter, Ann. Nat. Hist.
     (5) vii, p. 88 (1881).

     _Spongilla cerebellata_, Weltner, Arch. Naturg. lxi (i), p.
     117 (1895).

     _Spongilla cerebellata_, Kirkpatrick, Ann. Nat. Hist. (7)
     xx, p. 523 (1907).

This variety is distinguished from the typical form by the total absence
of flesh-spicules. The gemmule-spicules are also more numerous and cross
one another more regularly.


3_b_. Var. bengalensis*, _Annandale_. (Plate I, figs. 1-3.)

     _Spongilla lacustris_ var. _bengalensis_, Annandale, J.
     Asiat. Soc. Bengal, 1906, p. 56.

     _Spongilla alba_ var. _marina_, _id._, Rec. Ind. Mus. i, p.
     389 (1907).

The sponge is either devoid of branches or produces irregular,
compressed, and often digitate processes, sometimes of considerable
length and delicacy. Flesh-spicules are usually present throughout the
sponge, but are sometimes absent from one part of a specimen and present
in others. Some of the gemmules are often much smaller than the others.
Perhaps this form should be regarded as a phase rather than a true
variety (see p. 18).

All forms of _S. alba_ can be distinguished from all forms of _S.
lacustris_ by the much closer network of the skeleton and by the
consequent hardness of the sponge; also by the complete absence of green
corpuscles.

TYPES. The types of the species and of the var. _cerebellata_ are in the
British Museum, with fragments of the former in the Indian Museum; that
of var. _bengalensis_ is in the Indian Museum, with a co-type in London.

GEOGRAPHICAL DISTRIBUTION.--India And Egypt. _Localities_:--BOMBAY
PRESIDENCY, island of Bombay (_Carter_); Igatpuri, W. Ghats
(_Annandale_): BENGAL, Calcutta; Port Canning, Ganges delta (var.
_bengalensis_) (_Annandale_); Garia, Salt Lakes, nr. Calcutta (var.
_bengalensis_) (_B. L. Chaudhuri_); Chilka Lake, Orissa (var.
_bengalensis_) (_Gopal Chunder Chatterjee_): MADRAS PRESIDENCY, Rambha,
Ganjam district (_Annandale_): NIZAM'S TERRITORY, Aurangabad
(_Bowerbank_, var. _cerebellata_). The var. _cerebellata_ has also been
taken near Cairo.

BIOLOGY.--The typical form of the species is usually found growing on
rocks or bricks at the edges of ponds, while the variety _bengalensis_
abounds on grass-roots in pools and swamps of brackish water in the
Ganges delta and has been found on mussel-shells (_Modiola jenkinsi_,
Preston) in practically salt water in the Chilka Lake. Carter procured
the typical form at Bombay on stones which were only covered for six
months in the year, and "temporarily on floating objects." In Calcutta
this form flourishes in the cold weather on artificial stonework in the
"tanks" together with _S. carteri_, _S. fragilis_, _Ephydatia meyeni_,
and _Trochospongilla latouchiana_.

The variety _bengalensis_ is best known to me as it occurs in certain
ponds of brackish water at Port Canning on the Mutlah River, which
connects the Salt Lakes near Calcutta with the sea. It appears in these
ponds in great luxuriance every year at the beginning of the cold
weather and often coats the whole edge for a space of several hundred
feet, growing in irregular masses which are more or less fused together
on the roots and stems of a species of grass that flourishes in such
situations. Apparently the tendency for the sponges to form branches is
much more marked in some years than in others (see Pl. I, figs. 1-3).
The gemmules germinate towards the end of the "rains," and large masses
of sponge are not formed much before December. At this season, however,
the level of the water in the ponds sinks considerably and many of the
sponges become dry. If high winds occur, the dry sponges are broken up
and often carried for considerable distances over the flat surrounding
country. In January the gemmules floating on the surface of the ponds
form a regular scum. _S. alba_ var. _bengalensis_ is the only sponge
that occurs in these ponds at Port Canning, but _S. lacustris_, subsp.
_reticulata_, is occasionally found with it on brickwork in the ditches
that drain off the water from the neighbouring fields into the Mutlah
estuary. The latter sponge, however, perishes as these ditches dry up,
at an earlier period than that at which _S. alba_ reaches its maximum
development.

The larvæ of _Sisyra indica_ are commonly found in the oscula of the
typical form of _S. alba_ as well as in those of _S. lacustris_ subsp.
_reticulata_, and _S. carteri_; but the compact structure of the sponge
renders it a less suitable residence for other _incolæ_ than _S.
carteri_.

In the variety _bengalensis_, as it grows in the ponds at Port Canning,
a large number of arthropods, molluscs and other small animals take
shelter. Apart from protozoa and rotifers, which have as yet been little
studied, the following are some of the more abundant inhabitants of the
sponge:--The sea-anemone, _Sagartia schilleriana_ subsp. _exul_ (see p.
140), which frequently occurs in very large numbers in the broader
canals; the free-living nematode, _Oncholaimus indicus_[W], which makes
its way in and out of the oscula; molluscs belonging to several species
of the genus _Corbula_, which conceal themselves in the canals but are
sometimes engulfed in the growing sponge and so perish; young
individuals of the crab _Varuna litterata_, which hide among the
branches and ramifications of the larger sponges together with several
small species of prawns and the schizopod _Macropsis orientalis_[X]; the
peculiar amphipod _Quadrivisio bengalensis_[Y], only known from the
ponds at Port Canning, which breeds in little communities inside the
sponge; a small isopod[Z], allied to _Sphæroma walkeri_, Stebbing; the
larva of a may-fly, and those of at least two midges (Chironomidæ).

     [Footnote W: O. von Linstow, Rec. Ind. Mus. i, p. 45
     (1907).]

     [Footnote X: W. M. Tattersall, _ibid._, ii, p. 236 (1908).]

     [Footnote Y: T. R. R. Stebbing, _ibid._, i, p. 160 (1907);
     and N. Annandale, _ibid._, ii, p. 107 (1908).]

     [Footnote Z: Mr. Stebbing has been kind enough to examine
     specimens of this isopod, which he will shortly describe in
     the Records of the Indian Museum. _S. walkeri_, its nearest
     ally, was originally described from the Gulf of Manaar,
     where it was taken in a tow-net gathering (see Stebbing in
     Herdman's Report on the Ceylon Pearl Fisheries, pt. iv, p.
     31 (1905)).]

The peculiarly mixed nature (marine and lacustrine) of the fauna
associated with _S. alba_ in the ponds at Port Canning is well
illustrated by this list, and it only remains to be stated that little
fish (_Gobius alcockii_, _Barbus stigma_, _Haplochilus melanostigma_,
_H. panchax_, etc.) are very common and feed readily on injured sponges.
They are apparently unable to attack a sponge so long as its external
membrane is intact, but if this membrane is broken, they swarm round the
sponge and devour the parenchyma greedily. In fresh water one of these
fishes (_Gobius alcockii_, see p. 94) lays its eggs in sponges.

The chief enemy of the sponges at Port Canning is, however, not an
animal but a plant, viz., a green filamentous alga which grows inside
the sponge, penetrating its substance, blocking up its canals and so
causing it to die. Similar algæ have been described as being beneficial
to the sponges in which they grow[AA], but my experience is that they
are deadly enemies, for the growth of such algæ is one of the
difficulties which must be fought in keeping sponges alive in an
aquarium. The alga that grows in _S. alba_ often gives it a dark green
colour, which is, however, quite different from the bright green caused
by the presence of green corpuscles. The colour of healthy specimens of
the variety _bengalensis_ is a rather dark grey, which appears to be due
to minute inorganic particles taken into the cells of the parenchyma
from the exceedingly muddy water in which this sponge usually grows. If
the sponge is found in clean water, to whichever variety of the species
it belongs, it is nearly white with a slight yellowish tinge. Even when
the typical form is growing in close proximity to _S. proliferens_, as
is often the case, no trace of green corpuscles is found in its cells.

     [Footnote AA: See M. and A. Weber in M. Weber's Zool. Ergeb.
     Niederl. Ost-Ind. vol. i, p. 48, pl. v (1890).]


4. Spongilla cinerea*, _Carter_.

     _Spongilla cinerea_, Carter, J. Bombay Soc. iii, p. 30, pl.
     i, fig. 5, & Ann. Nat. Hist. (2) iv, p. 82, pl. iii, fig. 5
     (1849).

     _Spongilla cinerea_, Bowerbank, P. Zool. Soc. London, 1863,
     p. 468, pl. xxxviii, fig. 19.

     _Spongilla cinerea_, Carter, Ann. Nat. Hist. (5) vii, p. 263
     (1881).

_Sponge_ forming large, flat sheets, never more than a few millimetres
in thickness, without a trace of branches, compact but very friable, of
a dark greyish colour; oscula small and inconspicuous or moderately
large, never prominent; membrane adhering closely to the sponge.

_Skeleton_ with well-defined but slender radiating fibres, which contain
very little spongin; transverse fibres close together but consisting for
the most part of one or two spicules only.

_Spicules._ Skeleton-spicules short, slender, sharply pointed, minutely
serrated or irregular in outline, almost straight. Gemmule-spicules very
small, rather stout, cylindrical, pointed, covered with relatively long
and stout spines which are either straight or directed towards the ends
of the spicule. Flesh-spicules fairly numerous in the external membrane
but by no means abundant in the parenchyma, very slender, gradually
pointed, covered uniformly with minute but distinct spines.

_Gemmules_ very small, only visible to the naked eye as minute specks,
as a rule numerous, free in the substance of the sponge, each provided
with a slender foraminal tubule and covered with a thick granular coat
in which the gemmule-spicules are arranged almost horizontally; a
horizontal layer of spicules also present on the external surface of the
gemmule; gemmule-spicules very numerous.

[Illustration: Fig. 10.--Gemmules and fragment of the skeleton of
_Spongilla cinerea_ (from type specimen), × 35.]

This sponge is easily distinguished from its Indian allies by the form
of its skeleton-spicules, which are, as Bowerbank expresses it,
"subspined"; that it to say, under a high power of the microscope their
outline appears to be very minutely serrated, although under a low power
they seem to be quite smooth. The spicules also are smaller than those
of _S. alba_, the only species with which _S. cinerea_ is likely to be
confused, and the gemmule has a well-developed foraminal tubule; the
skeleton is much closer than in _S. proliferens_.

TYPE in the British Museum; a piece in the Indian Museum.

GEOGRAPHICAL DISTRIBUTION.--_S. cinerea_ is only known from the Bombay
Presidency. Carter obtained the original specimens at Bombay and the
only ones I have found were collected at Nasik, which is situated on the
eastern slopes of the Western Ghats, about 90 miles to the north-east.

BIOLOGY.--Carter's specimens were growing on gravel, rocks and stones at
the edge of "tanks," and were seldom covered for more than six months in
the year. Mine were on the sides of a stone conduit built to facilitate
bathing by conveying a part of the water of the Godaveri River under a
bridge. They were accompanied by _Spongilla indica_ and _Corvospongilla
lapidosa_ (the only other sponges I have found in running water in
India) and in the month of November appeared to be in active growth.


5. Spongilla travancorica*, _Annandale_.

     _Spongilla travancorica_, Annandale, Rec. Ind. Mus. iii, p.
     101, pl. xii, fig. 1 (1909).

_Sponge_ small, encrusting, without branches, hard but brittle; its
structure somewhat loose; colour dirty white. Dermal membrane in close
contact with the skeleton; pores and oscula inconspicuous. Surface
minutely hispid, smooth and rounded as a whole.

_Skeleton_ consisting of moderately stout and coherent radiating fibres
and well-defined transverse ones; a number of horizontal megascleres
present at the base and surface, but not arranged in any definite order.
No basal membrane.

[Illustration: Fig. 11.--Microscleres of _Spongilla travancorica_.

A=Gemmule-spicules; B=flesh-spicules (from type specimen), × 240.]

_Spicules._ Skeleton-spicules smooth, pointed at either end, moderately
stout, straight or curved, sometimes angularly bent; curvature usually
slight. Free microscleres abundant in the dermal membrane, slender,
nearly straight, gradually and sharply pointed, profusely ornamented
with short straight spines, which are much more numerous and longer at
the middle than near the ends. Gemmule-spicules stouter and rather
longer, cylindrical, terminating at each end in a sharp spine,
ornamented with shorter spines, which are more numerous and longer at
the ends than at the middle; at the ends they are sometimes directed
backwards, without, however, being curved.

_Gemmules_ firmly adherent to the support of the sponge, at the base of
which they form a layer one gemmule thick; each provided with at least
one foraminal tubule, which is straight and conical: two tubules, one at
the top and one at one side, usually present. Granular layer well
developed. Spicules arranged irregularly in this layer, as a rule being
more nearly vertical than horizontal but pointing in all directions, not
confined externally by a membrane; no external layer of horizontal
spicules.

  _Measurements of Spicules and Gemmules._

  Length of skeleton-spicules                 0.289-0.374 mm.
  Greatest diameter of skeleton-spicules      0.012-0.016  "
  Length of free microscleres                 0.08-0.096   "
  Greatest diameter of free microscleres      0.002 mm.
  Length of gemmule-spicules                  0.1-0.116    "
  Diameter of gemmule-spicule                 0.008 mm.
    "       " gemmule                         0.272-0.374  "

This species is easily distinguished from its allies of the subgenus
_Euspongilla_ by its adherent gemmules with their (usually) multiple
apertures and rough external surface.

TYPE in the collection of the Indian Museum.

HABITAT. Backwater near Shasthancottah, Travancore, in slightly brackish
water; on the roots of shrubs growing at the edge; November, 1908
(_Annandale_).

The specimens were dead when found.


6. Spongilla hemephydatia*, _Annandale_.

     _Spongilla hemephydatia_, Annandale, Rec. Ind. Mus. iii, p.
     275 (1909).

[Illustration: Fig. 12.--Gemmule and spicules of _Spongilla
hemephydatia_ (from type specimen).]

_Sponge_ soft, fragile, amorphous, of a dirty yellow colour, with large
oscula, which are not conspicuously raised above the surface but open
into very wide horizontal channels in the substance of the sponge. The
oscular collars are fairly well developed, but the subepidermal space is
not extensive.

_Skeleton_ diffuse, consisting of very fine radiating fibres, which are
crossed at wide and irregular intervals by still finer transverse ones;
very little chitinoid substance present.

_Spicules._ Skeleton-spicules smooth, slender, sharply pointed at both
ends, nearly straight. No true flesh-spicules. Gemmule-spicules straight
or nearly so, cylindrical, or constricted in the middle, obscurely
pointed or blunt, clothed with short, sharp, straight spines, which are
very numerous but not markedly longer at the two ends; these spicules
frequently found free in the parenchyma.

_Gemmules_ numerous, small, free, spherical, yellow, with a
well-developed granular coat (in which the spicules are arranged almost
horizontally) and external to it a fine membrane which in preserved
specimens becomes puckered owing to unequal contraction; each gemmule
with a single aperture provided with a straight, rather wide, but very
delicate foraminal tubule.

  _Measurements of Spicules and Gemmules._

  Length of skeleton-spicule       0.313 mm.
  Breadth of skeleton-spicule      0.012 "
  Length of gemmule-spicule        0.062 "
  Breadth of gemmule-spicule       0.004 "
  Diameter of gemmule              0.313-0.365 mm.

This sponge in its general structure bears a very close resemblance to
_Spongilla crateriformis_.

TYPE in the collection of the Indian Museum.

HABITAT. Growing on weeds at the edge of the Sur Lake, Orissa, October
1908. Only one specimen was taken, together with many examples of _S.
lacustris_ subsp. _reticulata_, _S. carteri_ and _S. crassissima_.


7. Spongilla crateriformis* (_Potts_).

     _Meyenia crateriforma_, Potts, P. Ac. Philad. 1882, p. 12.

     _Meyenia crateriformis, id., ibid._ 1887, p. 228, pl. v,
     fig. 6, pl. x, fig. 5.

     ? _Ephydatia crateriformis_, Hanitsch, Nature, ii, p. 511
     (1895).

     _Ephydatia crateriformis_, Weltner, Arch. Naturg. lxi (i),
     pp. 122, 134 (1895).

     ? _Ephydatia crateriformis_, Hanitsch, Irish Natural. iv, p.
     125, pl. iv, fig. 5 (1895).

     _Ephydatia indica_, Annandale, J. Asiat. Soc. Bengal, 1907,
     p. 20 (figures poor).

     _Ephydatia indica, id._, Rec. Ind. Mus. i, pp. 272, 279,
     388, 391 (1907).

     _Ephydatia crateriformis_, Scharff, European Animals, p. 34
     (1907).

     _Ephydatia crateriformis_, Annandale, P. U.S. Mus. xxxvii,
     p. 402, fig. 1 (1909).

_Sponge_ very fragile, forming soft irregular masses on the roots and
stems of water-plants, between which it is sometimes stretched as a
delicate film, or thin layers or cushions on flat surfaces. Oscula
large, flat, circular, or of irregular shape, opening into broad
horizontal canals, which at their distal end are superficial and often
covered by the external membrane only. Colour white, yellowish, greyish,
or blackish.

_Skeleton_ very delicate; radiating fibres rarely consisting of more
than two parallel spicules; transverse fibres far apart, frequently
consisting of single spicules; very little spongin present.

[Illustration: Fig 13.--Spicules of _Spongilla crateriformis_.

A. From specimen taken in July in a tank on the Calcutta maidan. B. From
type specimen of _Ephydatia indica_ taken in the Indian Museum tank in
winter. Both figures × 240.]

_Spicules._ Skeleton-spicules feebly curved, slender, as a rule
irregular in outline, sometimes almost smooth; the ends as a rule
sharply pointed, often constricted off and expanded so as to resemble
spear-heads, occasionally blunt. No true flesh-spicules.
Gemmule-spicules often free in the parenchyma, cylindrical, slender,
very variable in length in different sponges, straight or nearly so, as
a rule with an irregular circle of strong straight or recurved spines at
either end resembling a rudimentary rotule, and with shorter straight
spines scattered on the shaft, sometimes without the rudimentary rotule,
either truncate at the ends or terminating in a sharp spine.

_Gemmules_ small, free, each surrounded by a thick granular layer in
which the spicules stand upright or nearly so, and covered externally by
a delicate but very distinct chitinous membrane; no horizontal spicules;
foramen situated at the base of a crater-like depression in the granular
coat, which is sometimes raised round it so as to form a conspicuous
rampart; a short, straight foraminal tubule.

The shape of the spicules is extremely variable, and sponges in which
they are very different occur in the same localities and even in the
same ponds. It is possible that the differences are directly due to
slight changes in the environment, for in one pond in Calcutta a form
with _Spongilla_-like gemmule-spicules appears to replace the typical
form, which is common in winter, during the hot weather and "rains." I
have not, however, found this to be the case in other ponds. Perhaps _S.
hemephydatia_ will ultimately prove to be a variety of this very
variable species, but its smooth and regular skeleton-spicules and
short-spined gemmule-spicules afford a ready method of distinguishing it
from _S. crateriformis_. The two sponges are easily distinguished from
all others in the subgenus _Euspongilla_ by the upright and regular
arrangement of their gemmule-spicules, for although in _S. proliferens_
and _S. travancorica_ some of the gemmule-spicules are nearly vertical,
their arrangement is always irregular, a large proportion of the
spicules make an acute angle with the inner coat of the gemmule and a
few as a rule lie parallel to it. The systematic position of _S.
crateriformis_ is almost exactly intermediate between _Euspongilla_ and
_Ephydatia_, to which genus it has hitherto been assigned. I think,
however, that taking into consideration its close relationship to _S.
hemephydatia_, it is best to assign it to _Spongilla_, as its
rudimentary rotules never form distinct disks. I have examined some of
Potts's original specimens from different American localities and can
detect no constant difference between them and Indian specimens.

TYPES in the United States National Museum; co-types in Calcutta.

GEOGRAPHICAL DISTRIBUTION.--This sponge was originally described from
North America (in which continent it is widely distributed) and has been
recorded from the west of Ireland with some doubt. In India and Burma it
is widely distributed. BENGAL, Calcutta and neighbourhood (_Annandale_);
Sonarpur, Gangetic delta (_Annandale_); BOMBAY PRESIDENCY, Igatpuri
Lake, W. Ghats (altitude _ca._ 2,000 feet) (_Annandale_); MADRAS
PRESIDENCY, neighbourhood of Madras town (_J. R. Henderson_); Museum
compound, Egmore (Madras town) (_Annandale_); near Bangalore (alt. _ca._
3,000 ft.), Mysore State (Annandale); Ernakulam, Cochin (_G. Mathai_):
BURMA, Kawkareik, interior of Amherst district, Tenasserim, and the
Moulmein waterworks in the same district (_Annandale_).[AB]

     [Footnote AB: Mr. C. A. Paiva, Assistant in the Indian
     Museum, has lately (March 31st, 1911) obtained specimens of
     _S. crateriformis_ in a small pond of fresh water on Ross
     Island in the Andaman group. The existence of this widely
     distributed species on an oceanic island is noteworthy.]

BIOLOGY.--_S. crateriformis_ flourishes in Calcutta throughout the year.
Here it is usually found adhering to the roots of water-plants,
especially _Pistia_ and _Limnanthemum_. In the case of the former it
occurs at the surface, in that of the latter at the bottom. When growing
near the surface or even if attached to a stone at the bottom in clear
water, it is invariably of a pale yellowish or greyish colour. When
growing on the roots of _Limnanthemum_ in the mud of the Gangetic
alluvium, however, it is almost black, and when growing in the reddish
muddy waters of the tanks round Bangalore of a reddish-brown colour.
This appears to be due entirely to the absorption of minute particles of
inorganic matter by the cells of the parenchyma. If black sponges of the
species are kept alive in clean water, they turn pure white in less than
a week, apparently because these particles are eliminated. When growing
on stones the sponge, as found in India, often conforms exactly with
Potts's description: "a filmy grey sponge, branching off here and there
... yet with a curious lack of continuity...."

The wide efferent canals of this sponge afford a convenient shelter to
small crustacea, and the isopod _Tachæa spongillicola_, Stebbing (see p.
94), is found in them more abundantly than in those of any other sponge.
This is especially the case when the sponge is growing at the bottom. On
the surface of the sponge I have found a peculiar protozoon which
resembles the European _Trichodina spongillæ_ in general structure but
belongs, I think, to a distinct species, if not to a distinct genus.


Subgenus B. EUNAPIUS, _J. E. Gray_.

     _Eunapius_, J. E. Gray (_partim_), P. Zool. Soc. London,
     1867, p. 552.

     _Spongilla_ (_s. str._), Vejdovsky, in Potts's "Fresh-Water
     Sponges," P. Ac. Philad. 1887, p. 172.

     _Spongilla_ (_s. str._), Weltner, in Zacharias's Tier- und
     Pflanzenwelt des Süsswassers, i, p. 214 (1891).

     _Spongilla_ (_s. str._), Annandale, Zool. Jahrb., Syst.
     xxvii, p. 559 (1909).

TYPE, _Spongilla carteri_, Carter.

Spongillæ in which the gemmules are covered with layers of distinct
polygonal air-spaces with chitinous walls.

The gemmules are usually fastened together in groups, which may either
be free in the sponge or adhere to its support as a "pavement layer";
sometimes, however, they are not arranged in this manner, but are quite
independent of one another. The skeleton is usually delicate, sometimes
very stout (_e. g._, in _S. nitens_, Carter).

The term _Eunapius_ here used is not quite in the original sense, for
Gray included under it Bowerbank's _Spongilla paupercula_ which is now
regarded as a form of _S. lacustris_. His description, nevertheless,
fits the group of species here associated except in one particular,
viz., the smoothness of the gemmule-spicules to which he refers, for
this character, though a feature of _S. carteri_, is not  found in
certain closely allied forms. The use of "_Spongilla_" in a double sense
may be avoided by the adoption of Gray's name.

The subgenus _Eunapius_ is, like _Euspongilla_, cosmopolitan. It is not,
however, nearly so prolific in species. Four can be recognized in India,
two of which range, in slightly different forms, as far north as Europe,
one of them also being found in North America, Northern Asia, and
Australia.


8. Spongilla carteri* _Carter_ (_Bowerbank_, in litt.). (Plate II. fig.
1.)

     _Spongilla friabilis_?, Carter (_nec_ Lamarck), J. Bombay
     Asiat. Soc. iii, p. 31, pl. i, fig. 3 (1849), & Ann. Nat.
     Hist. (2) iv, p. 83, pl. ii. fig. 3 (1849).

     _Spongilla carteri_, Carter, Ann. Nat. Hist. (3) iii, p.
     334, pl. viii, figs. 1-7 (1859).

     _Spongilla carteri_, Bowerbank, P. Zool. Soc. London, 1863,
     p. 469, pl. xxxviii, fig. 20.

     _Eunapius carteri_, J. E. Gray, _ibid._ 1867, p. 552.

     _Spongilla carteri_, Carter, Ann. Nat. Hist. (5) vii, p. 86
     (1881).

     _Spongilla carteri_, _id._, _ibid._ x, p. 369 (1882).

     _Spongilla carteri_, Potts, P. Ac. Philad. 1887, p. 194.

     _Spongilla carteri_, Weltner, Arch. Naturg. lxi (i), pp.
     117, 134 (1895).

     _Spongilla carteri_, Kirkpatrick, P. Zool. Soc. London, 1906
     (i), p. 219, pl. xv, figs. 3, 4 (? figs. 1, 2).

     _Spongilla carteri_, Annandale, J. Asiat. Soc. Bengal, 1906,
     p. 188, pl. i, fig. 1.

     _Spongilla carteri_, Willey, Spolia Zeyl. iv, p. 184 (1907).

     _Spongilla carteri_, Annandale, _ibid._ vii, p. 63, pl. 1,
     fig. 1 (1910).

[Illustration: Fig. 14.--Gemmule of _Spongilla carteri_ (from Calcutta),
as seen in optical section, × 140.]

_Sponge_ massive, as a rule with the surface smooth and rounded,
occasionally bearing irregular ridges, which may even take the form of
cockscombs; the oscula large, rounded, conspicuous but not raised above
the surface of the sponge, leading into broad vertical canals; the
lateral canals, except in the immediate vicinity of the central vertical
ones, not very broad; the oscular collars extending for a considerable
distance over the oscula in living or well-preserved specimens, never
standing out from the surface; the oscula never surrounded by radiating
furrows. The inhalent pores surrounded externally by unmodified cells of
the external membrane. Colour greyish, sometimes with a flush of green
on the external surface.

The sponge has a peculiarly strong and offensive smell.

_Skeleton_ fairly compact, with well-developed radiating fibres; the
transverse fibres splayed out at either end so that they sometimes
resemble a pair of fans joined together by the handles (fig. 3, p. 33).
A moderate amount of spongin present.

_Spicules._ Skeleton-spicules smooth, pointed, nearly straight, never
very stout but somewhat variable in exact proportions. Gemmule-spicules
similar but much smaller. (There are no true flesh-spicules, but
immature skeleton-spicules may easily be mistaken for them.)

_Gemmules_ as a rule numerous, spherical or flattened at the base,
variable in size, each covered by a thick coat consisting of several
layers of relatively large polygonal air-spaces. A single aperture
surrounded by a crater-like depression in the cellular coat and provided
with a foraminal tubule resembling an inverted bottle in shape. (This
tubule, which does not extend beyond the surface of the cellular coat,
is liable to be broken off in dried specimens.) The spicules variable in
quantity, arranged irregularly among the spaces of the cellular coat and
usually forming a sparse horizontal layer on its external surface. Each
gemmule contained in a cage of skeleton-spicules, by the pressure of
which it is frequently distorted.


8_a._ Var. mollis*, nov.

This variety is characterized by a paucity of skeleton-spicules. The
sponge is therefore soft and so fragile that it usually breaks in pieces
if lifted from the water by means of its support. Owing to the paucity
of skeleton-spicules, which resemble those of the typical form
individually, the radiating and transverse fibres are extremely
delicate.

Common in Calcutta.


8_b._ Var. cava*, nov.

This variety is characterized by the fact that the oscula open into
broad horizontal canals, the roof of which is formed by a thin layer of
parenchyma and skeleton or, in places, of the external membrane only.
The skeleton is loose and fragile, and the living sponge has a peculiar
glassy appearance. In spirit the colour is yellowish, during life it is
greenish or white.

Taken at Bombay; November, 1907.


8_c._ Var. lobosa*, nov.

The greater part of the sponge in this variety consists of a number of
compressed but pointed vertical lobes, which arise from a relatively
shallow, rounded base, in which the oscula occur. The dried sponge has a
yellowish colour.

Apparently common in Travancore.

       *     *     *     *     *

I cannot distinguish these three "varieties"[AC] from the typical form
as distinct species; indeed, their status as varieties is a little
doubtful in two cases out of the three. Var. _cava_ appears to be a
variety in the strict sense of the word (see p. 18), for it was found on
the island of Bombay, the original locality of the species, growing side
by side with the typical form. Var. _lobosa_, however, should perhaps be
regarded as a subspecies rather than a variety, for I have received
specimens from two localities in the extreme south-west of India and
have no evidence that the typical form occurs in that part of the
country. Evidence, however, is rather scanty as regards the occurrence
of freshwater sponges in S. India. Var. _mollis_, again, may be a phase
directly due to environment. It is the common form in the ponds of
certain parts (_e. g._ in the neighbourhood of the Maidan and at
Alipore) of the Calcutta municipal area, but in ponds in other parts
(_e. g._ about Belgatchia) of the same area, only the typical form is
found. It is possible that the water in the former ponds may be
deficient in silica or may possess some other peculiarity that renders
the production of spicules difficult for _S. carteri_; but this seems
hardly probable, for _S. crassissima_, a species with a rather dense
siliceous skeleton, flourishes in the same ponds. I have noticed that in
ponds in which the aquatic vegetation is luxuriant and such genera of
plants as _Pistia_ and _Limnanthemum_ flourish, there is always a
tendency for _S. carteri_ to be softer than in ponds in which the
vegetation is mostly cryptogamic, and in Calcutta those parts of the
town in which sponges of this species produce most spicules are those in
which a slight infiltration of brackish water into the ponds may be
suspected; but in the interior of India, in places where the water is
absolutely fresh, hard specimens seem to be the rule rather than the
exception.

     [Footnote AC: The only complete European specimen of the
     species I have seen differs considerably in outward form
     from any Indian variety, consisting of a flat basal area
     from which short, cylindrical turret-like branches arise.
     This specimen is from Lake Balaton in Hungary and was sent
     me by Prof. von Daday de Dees of Buda-Pesth.]

_S. carteri_ is closely related to _S. nitens_, Carter (Africa, and
possibly S. America), but differs from that species in its comparatively
slender, sharp skeleton-spicules and smooth gemmule-spicules. It may
readily be distinguished from all other Indian freshwater sponges by its
large, deep, round oscula, but this feature is not so marked in var.
_lobosa_ as in the other forms. The typical form and var. _mollis_ grow
to a larger size than is recorded for any other species of the family. I
possess a specimen of the typical form from the neighbourhood of
Calcutta which measures 30 × 27 cm. in diameter and 19.5 cm. in depth,
and weighs (dry) 24-3/4 oz. The base of this specimen, which is solid
throughout, is nearly circular, and the general form is mound-shaped.
Another large specimen from Calcutta is in the form of an irregular
wreath, the greatest diameter of which is 34 cm. This specimen weighs
(dry) 16-1/4 oz. Both these specimens probably represent the growth of
several years.

TYPES.--The types of the varieties _mollis_, _cava_ and _lobosa_ are in
the collection of the Indian Museum. I regard as the type of the species
the specimen sent by Carter to Bowerbank and by him named _S. carteri_,
although, owing to some confusion, Carter's description under this name
appeared some years before Bowerbank's. This specimen is in the British
Museum, with a fragment in the Indian Museum.

GEOGRAPHICAL DISTRIBUTION.--The range of the species extends westwards
to Hungary, southwards to Mauritius and eastwards to the island of
Madura in the Malay Archipelago; a specimen from Lake Victoria Nyanza in
Central Africa has been referred to it by Kirkpatrick (P. Zool. Soc.
London, 1906 (i), p. 219), but I doubt whether the identification is
correct. In India _S. carteri_ is by far the most universally
distributed and usually much the commonest freshwater sponge; it is one
of the only two species as yet found in Ceylon. Specimens are known from
the following localities:--PUNJAB, Lahore (_J. Stephenson_): BOMBAY
PRESIDENCY, island of Bombay (_Carter_, _Kirkpatrick_, _Annandale_);
Igatpuri, W. Ghats (alt. _ca._ 2,000 ft.) (_Annandale_): UNITED
PROVINCES (plains), Agra (_Kirkpatrick_); Lucknow: HIMALAYAS, Bhim Tal,
Kumaon (alt. 4,500 ft.) (_Annandale_); Tribeni, Nepal (_Hodgart_):
BENGAL, Calcutta and neighbourhood; Rajshahi (Rampur Bhulia) on the R.
Ganges about 150 miles N. of Calcutta (_Annandale_); Berhampur,
Murshidabad district (_R. E. Lloyd_); Pusa, Darbbhanga district
(_Bainbrigge Fletcher_); Siripur, Saran district, Tirhut (_M.
Mackenzie_); Puri and the Sur Lake, Orissa (_Annandale_): MADRAS
PRESIDENCY, near Madras town (_J. R. Henderson_); Madura district (_R.
Bruce Foote_); Bangalore (_Annandale_) and Worgaum, Mysore State
(2,500-3,000 ft.); Ernakulam and Trichur, Cochin (_G. Mathai_);
Trivandrum and the neighbourhood of C. Comorin, Travancore (var.
_lobosa_) (_R. S. N. Pillay_): BURMA, Kawkareik, interior of Amherst
district, Tenasserim (_Annandale_); Rangoon (_Annandale_); Bhamo, Upper
Burma (_J. Coggin Brown_): CEYLON, Peradeniya (_E. E. Green_); outlet of
the Maha Rambaikulam between Vavuniya and Mamadu, Northern Province
(_Willey_); Horowapotanana, between Trincomalee and Anuradihapura,
North-Central Province (_Willey_).

BIOLOGY.--_S. carteri_ usually grows in ponds and lakes; I have never
seen it in running water. Mr. Mackenzie found it on the walls of old
indigo wells in Tirhut.

The exact form of the sponge depends to some extent on the forces acting
on it during life. At Igatpuri, for instance, I found that specimens
attached to the stems of shrubs growing in the lake and constantly
swayed by the wind had their surface irregularly reticulated with high
undulating ridges, while those growing on stones at the bottom of a
neighbouring pond were smooth and rounded.

Sponges of this species do not shun the light.

In Calcutta _S. carteri_ flourishes during the cold weather (November to
March). By the end of March many specimens that have attached themselves
to delicate stems such as those of the leaves of _Limnanthemum_, or to
the roots of _Pistia stratiotes_, have grown too heavy for their support
and have sunk down into the mud at the bottom of the ponds, in which
they are quickly smothered. Others fixed to the end of branches
overhanging the water or to bricks at the edge have completely dried up.
A large proportion, however, still remain under water; but even these
begin to show signs of decay at this period. Their cells migrate to the
extremities of the sponge, leaving a mass of gemmules in the centre, and
finally perish.

Few sponges exist in an active condition throughout the hot weather. The
majority of those that do so exhibit a curious phenomenon. Their surface
becomes smoothly rounded and they have a slightly pinkish colour; the
majority of the cells of their parenchyma, if viewed under a high power
of the microscope, can be seen to be gorged with very minute drops of
liquid. This liquid is colourless in its natural condition, but if the
sponge is plunged into alcohol the liquid turns of a dark brown colour
which stains both the alcohol and the sponge almost instantaneously.
Probably the liquid represents some kind of reserve food-material. Even
in the hot weather a few living sponges of the species may be found that
have not this peculiarity, but, in some ponds at any rate, the majority
that survive assume the peculiar summer form, which I have also found at
Lucknow.

Reproduction takes place in _S. carteri_ in three distinct ways, two of
which may be regarded as normal, while the third is apparently the
result of accident. If a healthy sponge is torn into small pieces and
these pieces are kept in a bowl of water, little masses of cells
congregate at the tips of the radiating fibres of the skeleton and
assume a globular form. At first these cells are homogeneous, having
clear protoplasm full of minute globules of liquid. The masses differ
considerably in size but never exceed a few millimetres in diameter. In
about two days differentiation commences among the cells; then spicules
are secreted, a central cavity and an external membrane formed, and an
aperture, the first osculum, appears in the membrane. In about ten days
a complete young sponge is produced, but the details of development have
not been worked out.

The most common normal form of reproduction is by means of gemmules,
which are produced in great numbers towards the end of the cold weather.
If small sponges are kept alive in an aquarium even at the beginning of
the cold weather, they begin to produce gemmules almost immediately, but
these gemmules although otherwise perfect, possess few or no
gemmule-spicules. If the sponge becomes desiccated at the end of the
cold weather and is protected in a sheltered place, some or all of the
gemmules contained in the meshes of its skeleton germinate _in situ_ as
soon as the water reaches it again during the "rains." It is by a
continuous or rather periodical growth of this kind, reassumed season
after season, that large masses of sponge are formed. In such masses it
is often possible to distinguish the growth of the several years, but as
a rule the layers become more or less intimately fused together, for no
limiting membrane separates them. A large proportion of the gemmules
are, however, set free and either float on the surface of the water that
remains in the ponds or are dried up and carried about by the wind. In
these circumstances they do not germinate until the succeeding cold
weather, even if circumstances other than temperature are favourable;
but as soon as the cold weather commences they begin to produce new
sponges with great energy.

Sexual reproduction, the second normal form, takes place in _S. carteri_
mainly if not only at the approach of a change of season, that is to say
about March, just before the hot weather commences, and about November,
just as the average temperature begins to sink to a temperate level. At
these seasons healthy sponges may often be found full of eggs and
embryos, which lie in the natural cavities of the sponge without
protecting membrane.

In the ponds of Calcutta a large number of animals are found associated
in a more or less definite manner with _Spongilla carteri_. Only one,
however, can be described with any degree of certainty as being in
normal circumstances an enemy, namely the larva of _Sisyra indica_,[AD]
and even in the case of this little insect it is doubtful how far its
attacks are actually injurious to the sponge. The larva is often found
in considerable numbers clinging to the oscula and wide efferent canals
of _S. carteri_, its proboscis inserted into the substance of the
sponge. If the sponge dies and the water becomes foul the larvæ swim or
crawl away. If the sponge dries up, they leave its interior (in which,
however, they sometimes remain for some days after it has become dry)
and pupate in a silken cocoon on its surface. Hence they emerge as
perfect insects after about a week.

     [Footnote AD: Needham. Rec. Ind. Mus. iii, p. 206 (1909).]

An animal that may be an enemy of _S. carteri_ is a flat-worm (an
undescribed species of _Planaria_) common in its larger canals and
remarkable for the small size of its pharynx. The same worm, however, is
also found at the base of the leaves of bulrushes and in other like
situations, and there is no evidence that it actually feeds on the
sponge. Injured sponges are eaten by the prawn _Palæmon lamarrei_,
which, however, only attacks them when the dermal membrane is broken. A
_Tanypus_ larva (Chironomid Diptera) that makes its way though the
substance of the sponge may also be an enemy; it is commoner in decaying
than in vigorous sponges.

The presence of another Chironomid larva (_Chironomus_, sp.) appears to
be actually beneficial. In many cases it is clear that this larva and
the sponge grow up together, and the larva is commoner in vigorous than
in decayed sponges. Unlike the _Tanypus_ larva, it builds parchment-like
tubes, in which it lives, on the surface of the sponge. The sponge,
however, often grows very rapidly and the larva is soon in danger of
being engulfed in its substance. The tube is therefore lengthened in a
vertical direction to prevent this catastrophe and to maintain
communication with the exterior. The process may continue until it is
over an inch in length, the older part becoming closed up owing to the
pressure of the growing sponge that surrounds it. Should the sponge die,
the larva lives on in its tubes without suffering, and the ends of tubes
containing larvæ may sometimes be found projecting from the worn surface
of dead sponges. The larva does not eat the sponge but captures small
insects by means of a pair of legs on the first segment of its thorax.
In so doing it thrusts the anterior part of its body out of the tube, to
the inner surface of which it adheres by means of the pair of false legs
at the tip of the abdomen. This insect, which is usually found in the
variety _mollis_, appears to do good to the sponge in two ways--by
capturing other insects that might injure it and by giving support to
its very feeble skeleton.

A precisely similar function, so far as the support of the sponge is
concerned, is fulfilled by the tubular zooecia of a phase of the
polyzoon _Plumatella fruticosa_ (see p. 218) which in India is more
commonly found embedded in the substance of _S. carteri_ than in that of
any other species, although in Great Britain it is generally found in
that of _S. lacustris_, which is there the commonest species of
freshwater sponge.

Another animal that appears to play an active part in the oeconomy of
the sponge is a peculiar little worm (_Chætogaster spongillæ_) also
found among the zooecia of _Plumatella_ and belonging to a widely
distributed genus of which several species are found in association with
pond-snails. _Chætogaster spongillæ_ often occurs in enormous numbers in
dead or dying sponges of _S. carteri_, apparently feeding on the
decaying organic matter of the sponge and assisting by its movements in
releasing numerous gemmules. In so doing it undoubtedly assists in the
dissemination of the species.

Major J. Stephenson (Rec. Ind. Mus. v, p. 233) has recently found two
other species of oligochætes inhabiting _S. carteri_ var. _lobosa_ from
Travancore. Both these species, unlike _Chætogaster spongillæ_, belong
to a genus that is vegetarian in habits. One of them, _Nais pectinata_,
has not yet been found elsewhere, while the other, _Nais communis_, has
a very wide distribution. The latter, however, occurs in the sponge in
two forms--one with eyes, the other totally blind. The blind form (_N.
communis_ var. _cæca_) has only been found in this situation, but the
other (var. _punjabensis_) lives free as well as in association with the
sponge, in which the blind form was the commoner of the two.

The majority of the animals found in association with _S. carteri_ gain
shelter without evident assistance to the sponge. This is the case as
regards the little fish (_Gobius alcockii_), one of the smallest of the
vertebrates (length about 1/2 inch), which lays its eggs in the patent
oscula, thus securing for them a situation peculiarly favourable to
their development owing to the constant current of water that passes
over them. In the absence of sponges, however, this fish attaches its
eggs to the floating roots of the water-plant _Pistia stratiotes_.
Numerous small crustacea[AE] also take temporary or permanent refuge in
the cavities of _S. carteri_, the most noteworthy among them being the
Isopod _Tachæa spongillicola_[AF], the adults of which are found in the
canal of this and other sponges, while the young cling to the external
surface of the carapace of _Palæmon lamarrei_ and other small prawns.
Many worms and insects of different kinds also enter the canals of _S.
carteri_, especially when the sponge is becoming desiccated; from
half-dry sponges numerous beetles and flies may be bred, notably the
moth-fly _Psychoda nigripennis_[AG] of which enormous numbers sometimes
hatch out from such sponges.

     [Footnote AE: According to the late Rai Bahadur R. B.
     Sanyal, freshwater sponges are called in Bengali "shrimps'
     nests." From his description it is evident that he refers
     mainly to _S. carteri_ (see Hours with Nature, p. 46;
     Calcutta 1896).]

     [Footnote AF: Stebbing, J. Linn. Soc. xxx, p. 40; Annandale,
     Rec. Ind. Mus. i, p. 279.]

     [Footnote AG: Brunetti, Rec. Ind. Mus. ii, p. 376 (1908).]

As the sponge grows it frequently attaches itself to small molluscs such
as the young of _Vivipara bengalensis_, which finally become buried in
its substance and thus perish. Possibly their decaying bodies may afford
it nourishment, but of the natural food of sponges we know little. _S.
carteri_ flourishes best and reaches its largest size in ponds used for
domestic purposes by natives of India, and thrives in water thick with
soap-suds. It is possible, though direct proof is lacking, that the
sponge does good in purifying water used for washing the clothes,
utensils, and persons of those who drink the same water, by absorbing
decaying animal and vegetable matter from it.

Various minute algæ are found associated with _S. carteri_, but of these
little is yet known. The green flush sometimes seen on the surface of
the typical form is due to the fact that the superficial cells of the
parenchyma contain green corpuscles. These, however, are never very
numerous and are not found in the inner parts of the sponge, perhaps
owing to its massive form. It is noteworthy that these green bodies
flourish in large numbers throughout the substance of sponges of _S.
proliferens_, a species always far from massive, growing in the same
ponds as _S. carteri_.


9. Spongilla fragilis, _Leidy_.

     _Spongilla fragilis_, Leidy, P. Ac. Philad. 1851, p. 278.

     _Spongilla lordii_, Bowerbank, P. Zool. Soc. London, 1863,
     p. 466, pl. xxxviii, fig. 17.

     _Spongilla contecta_, Noll, Zool. Garten*, 1870, p. 173.

     _Spongilla ottavænsis_, Dawson, Canad. Nat.* (new series)
     viii, p. 5 (1878).

     _Spongilla sibirica_, Dybowski, Zool. Anz., Jahr. i, p. 53
     (1878).

     _Spongilla morgiana_, Potts, P. Ac. Philad. 1880, p. 330.

     _Spongilla lordii_, Carter, Ann. Nat. Hist. (5) vii, p. 89,
     pl. vi, fig. 13 (1881).

     _Spongilla sibirica_, Dybowski, Mém. Ac. St. Pétersb. (7)
     xxx, no. x, p. 10, fig. 12.

     _Spongilla glomerata_, Noll, Zool. Anz., Jahr. ix, p. 682
     (1886).

     _Spongilla fragilis_, Vejdovsky, P. Ac. Philad. 1887, p.
     176.

     _Spongilla fragilis_, Potts, _ibid._ p. 197, pl. v, fig. 2;
     pl. viii, figs. 1-4.

     _Spongilla fragilis_, Weltner, Arch. Naturg. lix (1), p.
     266, pl. ix, figs. 18-20 (1893).

     _Spongilla fragilis_, _id._, Arch. Naturg. lxi (i), p. 117
     (1895).

     _Spongilla fragilis_, _id._, in Semon's Zool. Forsch. in
     Austral. u. d. Malay. Arch. v, part v, p. 523.

     _Spongilla fragilis_, Annandale, P. U.S. Mus. xxxvii, p. 402
     (1909).

     _Spongilla fragilis_, _id._, Annot. Zool. Japon. vii, part
     ii, p. 106, pl. ii, fig. 1 (1909).

_Sponge_ flat, lichenoid, never of great thickness, devoid of branches,
dense in texture but very friable; colour brown, green, or whitish;
oscula numerous, small, flat, distinctly star-shaped.

_Skeleton_ with well defined radiating and transverse fibres, which are
never strong but form a fairly dense network with a small amount of
spongin.

_Spicules._ Skeleton-spicules smooth, sharply pointed, moderately stout,
as a rule nearly straight. No flesh-spicules. Gemmule-spicules
cylindrical, blunt or abruptly pointed, nearly straight, covered with
relatively stout, straight, irregular spines, which are equally
distributed all over the spicule.

_Gemmules_ bound together in free groups of varying numbers and forming
a flat layer at the base of the sponge; each gemmule small in size,
surrounded by a thick cellular coat of several layers; with a relatively
long and stout foraminal tubule, which projects outwards through the
cellular coat at the sides of the group or at the top of the basal layer
of gemmules, is usually curved, and is not thickened at the tip; more
than one foraminal tubule sometimes present on a single gemmule;
gemmule-spicules arranged horizontally or at the base of the cellular
coat.

The species as a species is easily distinguished from all others, its
nearest ally being the N. American _S. ingloriformis_ with sparsely
spined skeleton-spicules which are very few in number, and gemmule
groups in which the foraminal tubules all open downwards.

Several varieties of _S. fragilis_ have been described in Europe and
America.

TYPE.--Potts refers to the type as being in the Academy of Natural
Sciences at Philadelphia.

GEOGRAPHICAL DISTRIBUTION.--All over Europe and N. America; also in
Siberia, Australia, and S. America. The species is included in this work
in order that its Asiatic local races may be fitly described.


9 _a._ Subsp. calcuttana*, nov.

     ? _Spongilla decipiens_, Weltner (_partim_), Arch. Naturg.
     lxi (i), pp. 117, 134 (1895).

     _Spongilla decipiens_, Annandale, Journ. As. Soc. Beng.
     1906, p. 57.

     _Spongilla fragilis_, _id._, Rec. Ind. Mus. i, p. 390
     (1907).

[Illustration: Fig. 15.--_Spongilla fragilis_ subsp. _calcuttana_.
A=group of gemmules, × 70; B=spicules, × 240. From type specimen.]

This local race, which is common in Calcutta, is distinguished from the
typical form mainly by the shape of its skeleton-spicules, most of which
are abruptly pointed or almost rounded at the tips, sometimes bearing a
minute conical projection at each end. The gemmule-spicules, which are
usually numerous, are slender. The foraminal tubules are usually long
and bent, but are sometimes very short and quite straight. The colour is
usually greyish, occasionally brown.

I have not found this race except in Calcutta, in the ponds of which it
grows on bricks or, very commonly, on the stems of bulrushes, often
covering a considerable area.

TYPE in the Indian Museum.


9 _b._ Subsp. decipiens*, _Weber_.

     _Spongilla decipiens_, Weber, Zool. Ergeb. Niederländ.
     Ost-Ind. i, p. 40, pl. iv, figs. 1-5 (1890).

This (?) local race is distinguished by the fact that the foraminal
tubules are invariably short and straight and thickened at the tips, and
that gemmule-spicules do not occur on the external surface of the
cellular coat of the gemmules.

I include Weber's _Spongilla decipiens_ in the Indian fauna on the
authority of Weltner, who identified specimens from the Museum "tank,"
Calcutta, as belonging to this form. All, however, that I have examined
from our "tank" belong to the subspecies _calcuttana_, most of the
skeleton-spicules of which are much less sharp than those of
_decipiens_. By the kindness of Prof. Max Weber I have been able to
examine a co-type of his species, which is probably a local race
peculiar to the Malay Archipelago.

TYPE in the Amsterdam Museum; a co-type in Calcutta.

Perhaps the Japanese form, which has spindle-shaped gemmule-spicules
with comparatively short and regular spines, should be regarded as a
third subspecies, and the Siberian form as a fourth.


10. Spongilla gemina*, sp. nov.

_Sponge_ forming small, shallow, slightly dome-shaped patches of a more
or less circular or oval outline, minutely hispid on the surface,
friable but moderately hard. Oscula numerous but minute and
inconspicuous, never star-shaped. Dermal membrane adhering closely to
the sponge. Colour grey or brown.

_Skeleton_ forming a close and regular network at the base of the
sponge, becoming rather more diffuse towards the external surface; the
radiating and the transverse fibres both well developed, of almost equal
diameter. Little spongin present.

_Spicules._ Skeleton-spicules slender, smooth, sharply pointed. No
flesh-spicules. Gemmule-spicules long, slender, cylindrical, blunt or
bluntly pointed, somewhat irregularly covered with minute straight
spines.

_Gemmules_ small, bound together in pairs, as a rule free in the
parenchyma but sometimes lightly attached at the base of the sponge.
Each gemmule flattened on the surface by which it is attached to its
twin, covered with a thin coat of polygonal air-spaces which contains
two layers of gemmule-spicules crossing one another irregularly in a
horizontal plane. One or two foraminal tubules present on the surface
opposite the flat one, bending towards the latter, often of considerable
length, cylindrical and moderately stout.

TYPE in the Indian Museum.

This species is closely allied to _S. fragilis_, from which it may be
distinguished by the curious twinned arrangement of its gemmules. It
also differs from _S. fragilis_ in having extremely small and
inconspicuous oscula.

_Locality._ I only know this sponge from the neighbourhood of Bangalore,
where Dr. Morris Travers and I found it in October, 1910 growing on
stones and on the leaves of branches that dipped into the water at the
edge of a large tank.


11. Spongilla crassissima*, _Annandale_.

     _Spongilla crassissima_, Annandale, J. Asiat. Soc. Bengal,
     1907, p. 17, figs. 2, 3.

     _Spongilla crassissima_, _id._, _ibid._ p. 88.

     _Spongilla crassissima_, _id._, Rec. Ind. Mus. i. p. 390,
     pl. xiv, fig. 4 (1907).

_Sponge_ very hard and strong, nearly black in colour, sometimes with a
greenish tinge, forming spherical, spindle-shaped or irregular masses
without branches but often several inches in diameter. Oscula circular
or star-shaped, usually surrounded by radiating furrows; pores normally
contained in single cells. External membrane closely adherent to the
sponge except immediately round the oscula.

_Skeleton_ dense, compact and only to be broken by the exercise of
considerable force; radiating and transverse fibres not very stout but
firmly bound together by spongin (fig. 6, p. 38), which occasionally
extends between them as a delicate film; their network close and almost
regular.

_Spicules._ Skeleton-spicules smooth, feebly curved, sausage-shaped but
by no means short, as a rule bearing at each end a minute conical
projection which contains the extremity of the axial filament. No
flesh-spicules. Gemmule-spicules closely resembling those of _S.
fragilis_ subsp. _calcuttana_, but as a rule even more obtuse at the
ends.

_Gemmules_ as in _S. fragilis_ subsp. _calcuttana_; a basal layer of
gemmules rarely formed.


11 _a._ Var. crassior*, _Annandale_.

     _Spongilla crassior_, Annandale, Rec. Ind. Mus. i, p. 389,
     pl. xiv, fig. 3 (1907).

This variety differs from the typical form chiefly in its even stronger
skeleton (fig. 3, p. 33) and its stouter skeleton-spicules, which do not
so often possess a terminal projection. The sponge is of a brownish
colour and forms flat masses of little thickness but of considerable
area on sticks and on the stems of water-plants.

TYPES.--The types of both forms are in the Indian Museum. Co-types have
been sent to London.

GEOGRAPHICAL DISTRIBUTION.--This sponge is only known from Bengal. The
variety _crassior_ was found at Rajshahi (Rampur Bhulia) on the Ganges,
about 150 miles N. of Calcutta, while the typical form is fairly common
in the "tanks" of Calcutta and very abundant in the Sur Lake near Puri
in Orissa.

[Illustration: Fig. 16.--Spicules of _Spongilla crassissima_ var.
_crassior_ (from type specimen), × 240.]

BIOLOGY.--_S. crassissima_ is usually found near the surface in shallow
water. Attached to the roots of the floating water-plant _Pistia
stratiotes_ it assumes a spherical form, while on sticks or like objects
it is spindle-shaped. Sometimes it is found growing on the same stick or
reed-stem as _S. carteri_, the two species being in close contact and
_S. carteri_ always overlapping _S. crassissima_. The dark colour is due
to minute masses of blackish pigment in the cells of the parenchyma. The
dense structure of the sponge is not favourable to the presence of
_incolæ_, but young colonies of the polyzoon _Plumatella fruticosa_ are
sometimes overgrown by it. Although they may persist for a time by
elongating their tubular zooecia through the substance of the sponge,
they do not in these circumstances reach the same development as when
they are overgrown by the much softer _S. carteri_.

_S. crassissima_ is found during the "rains" and the cold weather. In
Calcutta it attains its maximum size towards the end of the latter
season. In spite of its hard and compact skeleton, the sponge does not
persist from one cold weather to another.

A curious phenomenon has been noticed in this species, but only in the
case of sponges living in an aquarium, viz. the cessation during the
heat of the day of the currents produced by its flagella.


Subgenus C. STRATOSPONGILLA, _Annandale_.

     _Stratospongilla_, Annandale, Zool. Jahrb., Syst. xxvii, p.
     561 (1909).

TYPE, _Spongilla bombayensis_, Carter.

Spongillæ in the gemmules of which the pneumatic layer is absent or
irregularly developed, its place being sometimes taken by air-spaces
between the stout chitinous membranes that cover the gemmule. At least
one of these membranes is always present.

The gemmule-spicules lie in the membrane or membranes parallel to the
surface of the gemmule, and are often so arranged as to resemble a
mosaic. The gemmules themselves are usually adherent to the support of
the sponge. The chitinous membrane or membranes are often in continuity
with a membrane that underlies the base of the sponge. The skeleton is
usually stout, though often almost amorphous, and the skeleton-spicules
are sometimes sausage-shaped.

Sponges of this subgenus form crusts or sheets on solid submerged
objects.

_Stratospongilla_ is essentially a tropical subgenus, having its
head-quarters in Central Africa and Western India. One of its species,
however, (_S. sumatrana_*, Weber) occurs both in Africa and the Malay
Archipelago, while another has only been found in S. America (_S.
navicella_, Carter).

Aberrant species occur in China (_S. sinensis_*, _S. coggini_*) and the
Philippines (_S. clementis_*). Three species have been found in the
Bombay Presidency and Travancore, one of which (_S. bombayensis_*)
extends its range eastwards to Mysore and westwards across the Indian
Ocean to Natal.


12. Spongilla indica*, _Annandale_.

     _Spongilla indica_, Annandale, Rec. Ind. Mus. ii, p. 25,
     figs. 1, 2 (1908).

_Sponge_ forming a very thin layer, of a bright green or pale grey
colour; surface smooth, minutely hispid; pores and oscula inconspicuous,
the latter approached in some instances by radiating furrows; subdermal
cavity small; texture compact, rather hard.

_Skeleton_ incoherent, somewhat massive owing to the large number of
spicules present. Spicules forming triangular meshes and occasionally
arranged in vertical lines several spicules broad but without spongin.

_Spicules._ Skeleton-spicules straight or nearly straight, slender,
cylindrical, amphistrongylous, uniformly covered with minute, sharp
spines; flesh-spicules slender, sharply pointed, straight or curved,
irregularly covered with relatively long, straight sharp spines,
abundant in the dermal membrane, scarce in the substance of the sponge.
Gemmule-spicules short, stout, sausage-shaped, covered with minute
spines, which are sometimes absent from the extremities.

_Gemmules_ spherical, somewhat variable in size, with a single aperture,
which is provided with a trumpet-shaped foraminal tubule and is situated
at one side of the gemmule in its natural position; the inner chitinous
coat devoid of spicules, closely covered by an outer coat composed of a
darkly coloured chitinoid substance in which the gemmule-spicules are
embedded, lying parallel or almost parallel to the inner coat. The outer
coat forms a kind of mantle by means of the skirts of which the gemmule
is fastened to the support of the sponge. This coat is pierced by the
foraminal tubule.  The gemmules are distinct from one another.

[Illustration: Fig. 17.--Gemmule of _Spongilla indica_ seen from the
side (from type specimen), magnified.]

  Average length of skeleton-spicules       0.2046 mm.
     "   breadth of skeleton-spicules       0.0172  "
     "   length of flesh-spicules           0.053   "
     "   breadth of flesh-spicules          0.0053  "
     "   length of gemmule-spicules         0.044   "
     "   breadth of gemmule-spicules        0.0079  "

_S. indica_ is closely allied to _S. sumatrana_*, Weber, which has been
found both in the Malay Archipelago and in East Africa. It may be
distinguished by its blunt, almost truncated megascleres and
comparatively slender gemmule-spicules.

TYPE in the Indian Museum.

HABITAT, etc.--Growing, together with _S. cinerea_ and _Corvospongilla
lapidosa_, on the stone sides of an artificial conduit in the R.
Godaveri at Nasik on the eastern side of the Western Ghats in the Bombay
Presidency. The water was extremely dirty and was used for bathing
purposes. The sponge was green where the light fell upon it, grey where
it was in the shadow of the bridge under which the conduit ran. The only
specimens I have seen were taken in November, 1907.


13. Spongilla bombayensis*, _Carter_. (Plate II, fig. 2.)

     _Spongilla bombayensis_, Carter, Ann. Nat. Hist. (5) x, p.
     369, pl. xvi, figs. 1-6 (1882).

     _Spongilla bombayensis_, Annandale, Zool. Jahrb., Syst.
     xxvii, p. 562, figs. B, C (1909).

_Sponge_ hard but friable, forming thin layers or cushions; its surface
often irregular but without a trace of branches; its area never very
great; oscula inconspicuous; external membrane adhering closely to the
sponge; colour brownish or greyish.

[Illustration: Fig. 18.--Gemmule of _Spongilla bombayensis_ as seen from
above (from type specimen), magnified.]

_Skeleton_ almost amorphous, very dense, consisting of large numbers of
spicules arranged irregularly; radiating fibres occasionally visible in
sections, but almost devoid of spongin; a more or less definite
reticulation of horizontal spicules lying immediately under the external
membrane.

_Spicules._ Skeleton-spicules slender, pointed, feebly curved,
irregularly roughened or minutely spined all over the surface.
Flesh-spicules straight, narrowly rhomboidal in outline, sharply
pointed, slender, covered with minute, irregular, straight spines,
scanty in the parenchyma, abundant in the external membrane.
Gemmule-spicules sausage-shaped or bluntly pointed, variable in length
but usually rather stout, covered with minute spines, as a rule
distinctly curved.

_Gemmules_ round or oval, firmly adherent[AH] to the base of the sponge,
as a rule rather shallowly dome-shaped, covered by two thick chitinous
membranes, in each of which there is a dense horizontal layer of
spicules; no granular or cellular covering; the two chitinous coats
separated by an empty space; the aperture or apertures on the side of
the gemmule in its natural position, provided with foraminal tubules,
which may be either straight or curved, project through the outer
chitinous membrane and often bend down towards the base of the gemmule.
The spicules of the outer layer often more irregular in outline and less
blunt than those of the inner layer.

     [Footnote AH: The outer covering by means of which the
     gemmule is fixed is not formed until the other structures
     are complete. In young sponges, therefore, free gemmules may
     often be found.]

This sponge is allied to _S. indica_, but is distinguished among other
characters by its sharp skeleton-spicules and by the fact that the
gemmule is covered by two chitinous membranes instead of one.

TYPE in the British Museum; a fragment in the Indian Museum.

GEOGRAPHICAL DISTRIBUTION.--S. and W. India and S. Africa. Carter's type
was found in the island of Bombay, my own specimens in Igatpuri Lake in
the Western Ghats. I have recently (October 1910) found sponges and bare
gemmules attached to stones at the end of a tank about 10 miles from
Bangalore (Mysore State) in the centre of the Madras Presidency. Prof.
Max Weber obtained specimens in Natal.

BIOLOGY.--The specimens collected by Prof. Weber in Natal and those
collected by myself in the Bombay Presidency were both obtained in the
month of November. It is therefore very interesting to compare them from
a biological point of view. In so doing, it must be remembered that
while in S. Africa November is near the beginning of summer, in India it
is at the beginning of the "cold weather," that is to say, both the
coolest and the driest season of the year. The lake in which my
specimens were obtained had, at the time when they were collected,
already sunk some inches below its highest level, leaving bare a gently
sloping bank of small stones. Adhering to the lower surface of these
stones I found many small patches of _Spongilla bombayensis_, quite dry
but complete so far as their harder parts were concerned and with the
gemmules fully formed at their base. From the shallow water at the edge
of the lake I took many similar stones which still remained submerged.
It was evident that the sponge had been just as abundant on their lower
surface as on that of the stones which were now dry; but only the
gemmules remained, sometimes with a few skeleton-spicules adhering to
them (Pl. II, fig. 2). The bulk of the skeleton had fallen away and the
parenchyma had wholly perished. In a few instances a small sponge, one
or two millimetres in diameter, had already been formed among the
gemmules; but these young sponges appeared to belong to some other
species, possibly _Spongilla indica_, which was also common in the lake.

Carter's specimen of _S. bombayensis_, which was evidently in much the
same condition as those I found still submerged a month later, was taken
in October in a disused quarry. It was surrounded by a mass of _S.
carteri_ three inches in diameter, and was attached to a herbaceous
annual. The point on the edge of the quarry at which this plant grew was
not reached by the water until July. It is therefore necessary to assume
that the gemmules of _S. bombayensis_ had been formed between July and
October. Probably the larva of the sponge had settled down on the plant
during the "rains"--which commence in Bombay about the beginning of
June--and had grown rapidly. The production of gemmules may have been
brought about owing to the sponge being choked by the more vigorous
growth of _S. carteri_, a species which grows to a considerable size in
a comparatively short time, while _S. bombayensis_ apparently never
reaches a thickness of more than a few millimetres.

The manner in which the gemmules of _S. bombayensis_ are fastened to the
solid support of the sponge must be particularly useful in enabling them
to sprout in a convenient environment as soon as the water reaches them.
The fact that the gemmules remained fixed without support renders it
unnecessary for the skeleton to persist as a cage containing them (or at
any rate a proportion of them) during the period of rest.

Prof. Weber's specimens of _S. bombayensis_ were collected in a river,
apparently on stones or rocks, towards the beginning of the S. African
summer. They contain comparatively few gemmules and were evidently in a
vigorous condition as regards vegetative growth. Unfortunately we know
nothing of the seasonal changes which take place in freshwater sponges
in S. Africa, but the difference between these changes in Europe and in
India shows that they are dependent on environment as well as the
idiosyncrasy of the species. It is very interesting, therefore, to see
that the condition of sponges taken in S. Africa differs so widely from
that of other individuals of the same species taken in India at the same
season.

In Prof. Weber's specimens I have found numerous small tubules of
inorganic débris. These appear to be the work of Chironomid larvæ, of
which there are several specimens loose in the bottle containing the
sponges. Other tubules of a very similar appearance but with a delicate
chitinoid foundation appear to be the remains of a species of
_Plumatella_ of which they occasionally contain a statoblast.


14. Spongilla ultima*, _Annandale_. (Plate II, fig. 3.)

     _Spongilla ultima_, Annandale, Rec. Ind. Mus. v, p. 31 (1910).

_Sponge_ hard and strong, forming a thin layer on solid objects, of a
pale green colour (dry); the oscula small but rendered conspicuous by
the deep radiating furrows that surround them; external surface of the
sponge rough but not spiny.

_Skeleton_ forming a compact but somewhat irregular reticulation in
which the radiating fibres are not very much more distinct than the
transverse ones; a considerable amount of almost colourless spongin
present.

_Spicules._ Skeleton-spicules smooth, stout, amphioxous, as a rule
straight or nearly straight, not infrequently inflated in the middle or
otherwise irregular. No flesh-spicules. Gemmule-spicules variable in
size, belonging to practically every type and exhibiting practically
every abnormality possible in the genus, the majority being more or less
sausage-shaped and having a roughened surface, but others being
cruciform, spherical, subspherical, rosette-like, needle-like, bifid or
even trifid at one extremity.

[Illustration: Fig. 19.--Spicules of _Spongilla ultima_ (from type
specimen), × 120.]

_Gemmules_ adherent, spherical, large, each covered by two distinct
layers of horizontal spicules; the outer layer intermixed with
skeleton-spicules and often containing relatively large siliceous
spheres, a large proportion of the spicules being irregular in shape;
the spicules of the inner layer much more regular and as a rule
sausage-shaped. The outer layer is contained in a chitinous membrane
which spreads out over the base of the sponge. The foraminal tubules are
short and straight.

This sponge is allied to _S. bombayensis_, from which it is
distinguished not only by the abnormal characters of its
gemmule-spicules and the absence of flesh-spicules, but also by the form
of its skeleton-spicules and the structure of its skeleton. I have
examined several specimens dry and in spirit; but _S. ultima_ is the
only Indian freshwater sponge, except _Corvospongilla burmanica_, I have
not seen in a fresh condition.

TYPES in the Indian Museum; co-types at Trivandrum.

HABITAT. Discovered by Mr. R. Shunkara Narayana Pillay, of the
Trivandrum Museum, in a tank near Cape Comorin, the southernmost point
of the Indian Peninsula.


Genus 2. PECTISPONGILLA, _Annandale_.

     _Pectispongilla_, Annandale, Rec. Ind. Mus. iii, p. 103 (1909).

TYPE, _Pectispongilla aurea_, Annandale.

The structure of the sponge resembling that of _Euspongilla_ or
_Ephydatia_; but the gemmule-spicules bear at either end, at one side
only, a double vertical row of spines, so that they appear when viewed
in profile like a couple of combs joined together by a smooth bar.

[Illustration: Fig. 20.--Gemmule and spicules of _Pectispongilla aurea_
(type specimen). _a_, Skeleton-spicules; _b_, gemmule-spicules; _b'_, a
single gemmule-spicule more highly magnified.]

GEOGRAPHICAL DISTRIBUTION.--The genus is monotypic and is only known
from Travancore and Cochin in the south-west of the Indian Peninsula.


15. Pectispongilla aurea*, _Annandale_.

     _Pectispongilla aurea_, Annandale, _op. cit._, p. 103, pl.
     xii, fig. 2.

_Sponge_ forming minute, soft, cushion-like masses of a deep golden
colour (dull yellow in spirit); the surface smooth, minutely hispid. One
relatively large depressed osculum usually present in each sponge; pores
inconspicuous; dermal membrane in close contact with the parenchyma.

_Skeleton_ consisting of slender and feebly coherent radiating fibres as
a rule two or three spicules thick, with single spicules or ill-defined
transverse fibres running horizontally. Towards the  external surface
transverse spicules are numerous, but they do not form any very regular
structure.

_Spicules._ Skeleton-spicules smooth, sharply pointed, straight or
nearly so. Gemmule-spicules minute, with the stem smooth and
cylindrical, relatively stout and much longer than the comb at either
end; the two combs equal, with a number of minute, irregularly scattered
spines between the two outer rows of stouter ones. No free microscleres.

_Gemmules_ minute, spherical, with a single aperture, which is provided
with a very short foraminal tubule; the granular coat well developed;
the spicules arranged in a slanting position, but more nearly vertically
than horizontally, with the combs pointing in all directions; no
external chitinous membrane.

  Length of skeleton-spicule                     0.2859 mm.
  Greatest diameter of skeleton-spicule          0.014  "
  Length of gemmule-spicule                      0.032-0.036 mm.
  Length of comb of gemmule-spicule              0.008 mm.
  Greatest diameter of shaft of gemmule-spicule  0.004  "
  Diameter of gemmule                            0.204-0.221 mm.

The gemmule-spicules first appear as minute, smooth, needle-like bodies,
which later become roughened on one side at either end and so finally
assume the mature form. There are no bubble-cells in the parenchyma.


15_a._ Var. subspinosa*, nov.

This variety differs from the typical form in having its skeleton
spicules covered with minute irregular spines or conical projections.

TYPES of both the typical form and the variety in the Indian Museum;
co-types of the typical form in the Trivandrum Museum.

GEOGRAPHICAL DISTRIBUTION.--The same as that of the genus.
_Localities_:--Tenmalai, at the base of the western slopes of the W.
Ghats in Travancore (typical form) (_Annandale_); Ernakulam and Trichur
in Cochin (var. _subspinosa_) (_G. Mathai_).

BIOLOGY.--My specimens, which were taken in November, were growing on
the roots of trees at the edge of an artificial pool by the roadside.
They were in rather dense shade, but their brilliant golden colour made
them conspicuous objects in spite of their small size. Mr. Mathai's
specimens from Cochin were attached to water-weeds and to the husk of a
cocoanut that had fallen or been thrown into the water.


Genus 3. EPHYDATIA, _Lamouroux_.

     _Ephydatia_, Lamouroux, Hist. des Polyp. corall. flex.* p. 6
     (_fide_ Weltner) (1816).

     _Ephydatia_, J. E. Gray, P. Zool. Soc. London. 1867, p. 550.

     _Trachyspongilla_, Dybowsky (_partim_), Zool. Anz. i, p. 53
     (1874).

     _Meyenia_, Carter (_partim_), Ann. Nat. Hist. (5) vii, p. 90
     (1881).

     _Carterella_, Potts & Mills (_partim_), P. Ac. Philad. 1881,
     p. 150.

     _Ephydatia_, Vejdovsky, Abh. Böhm. Ges. xii, p. 23 (1883).

     _Meyenia_, Potts (_partim_), _ibid._ 1887, p. 210.

     _Carterella_, _id._ (_partim_), _ibid._ 1887, p. 260.

     _Ephydatia_, Weltner (_partim_), Arch. Naturg. lxi (i), p.
     121 (1895).

     _Ephydatia_, Annandale, P. U.S. Mus. xxxvii, p. 404 (1909).

TYPE, (?) _Spongilla fluviatilis_, auctorum.

This genus is separated from _Spongilla_ by the structure of the
gemmule-spicules, which bear at either end a transverse disk with
serrated or deeply notched edges, or at any rate with edges that are
distinctly undulated. The disks are equal and similar. True
flesh-spicules are usually absent, but more or less perfect birotulates
exactly similar to those associated with the gemmules are often found
free in the parenchyma. The skeleton is never very stout and the
skeleton-spicules are usually slender.

As has been already stated, some authors consider _Ephydatia_ as the
type-genus of a subfamily distinguished from the subfamily of which
_Spongilla_ is the type-genus by having rotulate gemmule-spicules. The
transition between the two genera, however, is a very easy one. Many
species of the subgenus _Euspongilla_, the typical subgenus of
_Spongilla_ (including _S. lacustris_, the type-species of the genus),
have the spines at the ends of the gemmule-spicules arranged in such a
way as to suggest rudimentary rotules, while in the typical form of _S.
crateriformis_ this formation is so distinct that the species has
hitherto been placed in the genus _Ephydatia_ (_Meyenia_), although in
some sponges that agree otherwise with the typical form of the species
the gemmule-spicules are certainly not rotulate and in none do these
spicules bear definite disks.

GEOGRAPHICAL DISTRIBUTION.--_Ephydatia_, except _Spongilla_, is the most
generally distributed genus of the Spongillidæ, but in most countries it
is not prolific in species. In Japan, however, it appears to predominate
over _Spongilla_. Only one species is known from India, but another (_E.
blembingia_*, Evans) has been described from the Malay Peninsula, while
Weber found both the Indian species and a third (_E. bogorensis_*) in
the Malay Archipelago.


16. Ephydatia meyeni* (_Carter_).

     _Spongilla meyeni_, Carter, J. Bomb. Asiat. Soc. iii, p. 33,
     pl. i, fig. 1, & Ann. Nat. Hist. (2) iv, p. 84, pl. iii,
     fig. 1 (1849).

     _Spongilla meyeni_, Bowerbank, P. Zool. Soc. London, 1863,
     p. 448, pl. xxxviii, fig. 4.

     _Spongilla meyeni_, Carter, Ann. Nat. Hist. (5) vii, p. 93
     (1881).

     _Ephydatia fluviatilis_, Weber, Zool. Ergeb. Niederländ.
     Ost-Ind. i. pp. 32, 46 (1890).

     _Ephydatia mülleri_, Weltner (_partim_), Arch. Naturg. lxi
     (i), p. 125 (1895).

     _Ephydatia robusta_, Annandale, J. Asiat. Soc. Bengal, 1907,
     p. 24, fig. 7.

     _Ephydatia mülleri_ subsp. _meyeni_, _id._, Rec. Ind. Mus.
     ii, p. 306 (1908).

_Sponge_ hard and firm but easily torn, usually of a clear white,
sometimes tinged with green, forming irregular sheets or masses never of
great thickness, without branches but often with stout subquadrate
projections, the summits of which are marked with radiating grooves; the
whole surface often irregularly nodulose and deeply pitted; the oscula
inconspicuous; the membrane adhering closely to the parenchyma. _The
parenchyma contains numerous bubble-cells_ (see p. 31, fig. 2).

_Skeleton_ dense but by no means regular; the radiating fibres distinct
and containing a considerable amount of spongin, at any rate in the
outer part of the sponge; transverse fibres hardly distinguishable,
single spicules and irregular bundles of spicules taking their place.

[Illustration: Fig. 21.--Gemmule and spicules of _Ephydatia meyeni_
(from Calcutta). _a_, Skeleton-spicules; _b_, gemmule-spicules.]

_Spicules._ Skeleton-spicules entirely smooth, moderately stout, feebly
curved, sharply pointed. No flesh-spicules. Gemmule-spicules with the
shaft as a rule moderately stout, much longer than the diameter of one
disk, smooth or with a few stout, straight horizontal spines, which are
frequently bifid or trifid; the disks flat, of considerable size, with
their margins cleanly and deeply divided into a comparatively small
number of deep, slender, triangular processes of different sizes; the
shaft extending not at all or very little beyond the disks.

_Gemmules_ spherical, usually numerous and of rather large size; each
covered by a thick layer of minute air-spaces, among which the
gemmule-spicules are arranged vertically, often in two or even three
concentric series; a single short foraminal tubule; the pneumatic coat
confined externally by a delicate membrane, with small funnel-shaped
pits over the spicules of the outer series.

I think that the gemmules found by me in Bhim Tal and assigned to
Potts's _Meyenia robusta_ belong to this species, but some of the
spicules are barely as long as the diameter of the disks. In any case
Potts's description is so short that the status of his species is
doubtful. His specimens were from N. America.

_E. meyeni_ is closely related to the two commonest Holarctic species of
the genus, _E. fluviatilis_ and _E. mülleri_, which have been confused
by several authors including Potts. From _E. fluviatilis_ it is
distinguished by the possession of bubble-cells in the parenchyma, and
from _E. mülleri_ by its invariably smooth skeleton-spicules and the
relatively long shafts of its gemmule-spicules. The latter character is
a marked feature of the specimens from the Malay Archipelago assigned by
Prof. Max Weber to _E. fluviatilis_; I am indebted to his kindness for
an opportunity of examining some of them.

TYPE in the British Museum; a fragment in the Indian Museum.

GEOGRAPHICAL DISTRIBUTION.--India and Sumatra. _Localities_:--BENGAL,
Calcutta and neighbourhood (_Annandale_); MADRAS PRESIDENCY, Cape
Comorin, Travancore (_Trivandrum Mus._): BOMBAY PRESIDENCY, Island of
Bombay (_Carter_): HIMALAYAS, Bhim Tal, Kumaon (alt. 4,500 feet)
(_Annandale_).

BIOLOGY.--My experience agrees with Carter's, that this species is never
found on floating objects but always on stones or brickwork. It grows in
the Calcutta "tanks" on artificial stonework at the edge of the water,
together with _Spongilla carteri_, _S. alba_, _S. fragilis_ subsp.
_calcuttana_, and _Trochospongilla latouchiana_. It flourishes during
the cold weather and often occupies the same position in succeeding
years. In this event the sponge usually consists of a dead base, which
is of a dark brownish colour and contains no cells, and a living upper
layer of a whitish colour.

The larva of _Sisyra indica_ is sometimes found in the canals, but the
close texture of the sponge does not encourage the visits of other
_incolæ_.


Genus 4. DOSILIA, _Gray_.

     _Dosilia_, J. E. Gray, P. Zool. Soc. London, 1867, p. 550.

TYPE, _Spongilla plumosa_, Carter.

This genus is distinguished from _Ephydatia_ by the nature of the free
microscleres, the microscleres of the gemmule being similar in the two
genera. The free microscleres consist as a rule of several or many
shafts meeting together in several or many planes at a common centre,
which is usually nodular. The free ends of these shafts often possess
rudimentary rotulæ. Occasionally a free microsclere may be found that is
a true monaxon and sometimes such spicules are more or less distinctly
birotulate. The skeleton is also characteristic. It consists mainly of
radiating fibres which bifurcate frequently in such a way that a
bush-like structure is produced. Transverse fibres are very feebly
developed and are invisible to the naked eye. Owing to the structure of
the skeleton the sponge has a feathery appearance.

Gray originally applied the name _Dosilia_ to this species and to
_"Spongilla" baileyi_, Bowerbank. It is doubtful how far his generic
description applies to the latter, which I have not seen; but although
the position of _"Spongilla" baileyi_ need not be discussed here, I may
say that I do not regard it as a congener of _Dosilia plumosa_, the free
microscleres of which are of a nature rare but not unique in the family.
With _Dosilia plumosa_ we must, in any case, associate in one genus the
two forms that have been described as varieties, viz., _palmeri_*, Potts
from Texas and Mexico, and _brouini_*, Kirkpatrick from the White Nile.
By the kindness of the authorities of the Smithsonian Institution and
the British Museum I have been able to examine specimens of all three
forms, in each case identified by the author of the name, and I am
inclined to regard them as three very closely allied but distinct
species. Species with free microscleres similar to those of these three
forms but with heterogeneous or tubelliform gemmule-spicules will
probably need the creation of a new genus or new genera for their
reception.

GEOGRAPHICAL DISTRIBUTION.--The typical species occurs in Bombay and
Madras; _D. palmeri_ has probably an extensive range in the drier parts
of Mexico and the neighbouring States, while _D. brouini_ has only been
found on the banks of the White Nile above Khartoum, in Tropical Africa.


17. Dosilia plumosa* (_Carter_).

     _Spongilla plumosa_, Carter, J. Bomb. Asiat. Soc. iii, p.
     34, pl. i, fig. 2, & Ann. Nat. Hist. (2) iv, p. 85, pl. iii,
     fig. 2 (1849).

     _Spongilla plumosa_, Bowerbank, P. Zool. Soc. London, 1863,
     p. 449, pl. xxxviii, fig. 5.

     _Dosilia plumosa_, J. E. Gray, _ibid._ 1867, p. 551.

     _Meyenia plumosa_, Carter, Ann. Nat. Hist. (5) vii, p. 94,
     pl. v, fig. 6 (1881).

     _Meyenia plumosa_, Potts, P. Ac. Philad. 1887, p. 233.

     _Ephydatia plumosa_, Weltner, Arch. Naturg. lxi (i), p. 126
     (1895).

     _Ephydatia plumosa_, Petr, Rozp. Ceske Ak. Praze, Trída ii,
     pl. ii, figs. 29, 30 (text in Czech) (1899).

_Sponge_ forming soft irregular masses which are sometimes as much as 14
cm. in diameter, of a pale brown or brilliant green colour; no branches
developed but the surface covered with irregular projections usually of
a lobe-like nature.

_Skeleton_ delicate, with the branches diverging widely, exhibiting the
characteristic structure of the genus in a marked degree, containing a
considerable amount of chitin, which renders it resistant in spite of
its delicacy.

_Spicules._ Skeleton-spicules smooth, sharply pointed, nearly straight,
moderately slender, about twenty times as long as their greatest
transverse diameter. Flesh-spicules occasionally amphioxous or
birotulate and with a single shaft, more frequently consisting of many
shafts meeting in a distinct central nodule, which is itself smooth; the
shafts irregularly spiny, usually more or less nodular at the tip, which
often bears a distinct circle of recurved spines that give it a rotulate
appearance. Gemmule-spicules with long, slender, straight shafts, which
bear short, slender, straight, horizontal spines sparsely and
irregularly scattered over their surface; the rotulæ distinctly convex
when seen in profile; their edge irregularly and by no means deeply
notched; the shafts not extending beyond their surface but clearly seen
from above as circular umbones.

[Illustration: Fig. 22.--_Dosilia plumosa._

A=microscleres, × 240; B=gemmule as seen in optical section from
below, × 75. (From Rambha.)]

_Gemmules._ Somewhat depressed, covered with a thick granular pneumatic
coat, in which the spicules stand erect; the single aperture depressed.
Each gemmule surrounded more or less distinctly by a circle or several
circles of flesh-spicules.

TYPE in the British Museum; some fragments in the Indian Museum.

GEOGRAPHICAL DISTRIBUTION.--Bombay and Madras. Carter's specimens were
taken in the island of Bombay, mine at Rambha in the north-east of the
Madras Presidency. I have been unable to discover this species in the
neighbourhood of Calcutta, but it is apparently rare wherever it occurs.

BIOLOGY.--Carter writes as regards this species:--"This is the coarsest
and most resistant of all the species. As yet I have only found three or
four specimens of it, and these only in two tanks. I have never seen it
fixed on any solid body, but always floating on the surface of the
water, about a month after the first heavy rains of the S.W. monsoon
have fallen. Having made its appearance in that position, and having
remained there for upwards of a month, it then sinks to the bottom. That
it grows like the rest, adherent to the sides of the tank, must be
inferred from the first specimen which I found (which exceeds two feet
in circumference) having had a free and a fixed surface, the latter
coloured by the red gravel on which it had grown. I have noticed it
growing, for two successive years in the month of July, on the surface
of the water of one of the two tanks in which I have found it, and would
account for its temporary appearance in that position, in the following
way, viz., that soon after the first rains have fallen, and the tanks
have become filled, all the sponges in them appear to undergo a partial
state of putrescency, during which gas is generated in them, and
accumulates in globules in their structure, through which it must burst,
or tear them from their attachments and force them to the surface of the
water. Since then the coarse structure of _plumosa_ would appear to
offer greater resistance to the escape of this air, than that of any of
the other species, it is probable that this is the reason of my having
hitherto only found it in the position mentioned."

It seems to me more probable that the sponges are actually broken away
from their supports by the violence of the rain and retain air
mechanically in their cavities. The only specimens of _D. plumosa_ that
I have seen alive were attached very loosely to their support. In
writing of the "coarse structure" of this species, Carter evidently
alludes to the wide interspaces between the component branches of the
skeleton.

My specimens were attached to the stem of a water-lily growing in a pool
of slightly brackish water and were of a brilliant green colour. I
mistook them at first for specimens of _S. lacustris_ subsp.
_reticulata_ in which the branches had not developed normally. They were
taken in March and were full of gemmules. The pool in which they were
growing had already begun to dry up.


Genus 5. TROCHOSPONGILLA, _Vejdovsky_.

     _Trochospongilla_, Vejdovsky, Abh. K. Böhm. Ges. Wiss. xii,
     p. 31 (1883).

     _Trochospongilla_, Wierzejski, Arch. Slaves de Biologie, i,
     p. 44 (1886).

     _Trochospongilla_, Vejdovsky, P. Ac. Philad. 1887, p. 176.

     _Meyenia_, Potts (_partim_), _ibid._ p. 210.

     _Tubella_, _id._ (_partim_), _ibid._, p. 248.

     _Meyenia_, Carter (_partim_), Ann. Nat. Hist. (5) vii, p. 90
     (1881).

     _Trochospongilla_, Weltner, in Zacharias's Tier- und
     Pflanzenwelt, i, p. 215 (1891).

     _Trochospongilla_, _id._, Arch. Naturg. lxi (i), p. 120
     (1895).

     _Tubella_, _id._ (_partim_), _ibid._ p. 128.

TYPE, _Spongilla erinaceus_, Ehrenberg.

The characteristic feature of this genus is that the rotulæ of the
gemmule-spicules, which are homogeneous, have smooth instead of serrated
edges. Their stem is always short and they are usually embedded in a
granular pneumatic coat. The sponge is small in most of the species as
yet known; in some species microscleres without rotulæ are associated
with the gemmules.

[Illustration: Fig. 23.--A=skeleton-spicule of _Trochospongilla
latouchiana_; A'=gemmule-spicule of the same species; B=gemmule of _T.
phillottiana_ as seen in optical section from above; B'=skeleton-spicule
of same species: A, A', B' × 240; B × 75. All specimens from Calcutta.]

I think it best to include in this genus, as the original diagnosis
would suggest, all those species in which all the gemmule-spicules are
definitely birotulate and have smooth edges to their disks, confining
the name _Tubella_ to those in which the upper rotula is reduced to a
mere knob. Even in those species in which the two disks are normally
equal, individual spicules may be found in which the equality is only
approximate, while, on the other hand, it is by no means uncommon for
individual spicules in such species as _"Tubella" pennsylvanica_, which
is here included in _Trochospongilla_, to have the two disks nearly
equal, although normally the upper one is much smaller than the lower.
There is very rarely any difficulty, however, in seeing at a glance
whether the edge of the disk is smooth or serrated, the only species in
which this difficulty would arise being, so far as I am aware, the
Australian _Ephydatia capewelli_* (Haswell), the disks of which are
undulated and nodulose rather than serrated.

GEOGRAPHICAL DISTRIBUTION.--The genus includes so large a proportion of
small, inconspicuous species that its distribution is probably known but
imperfectly. It would seem to have its headquarters in N. America but
also occurs in Europe and Asia. In India three species have been found,
one of which (_T. pennsylvanica_) has an extraordinarily wide and
apparently discontinuous range, being common in N. America, and having
been found in the west of Ireland, the Inner Hebrides, and near the west
coast of S. India. The other two Indian species are apparently of not
uncommon occurrence in eastern India and Burma.


  _Key to the Indian Species of_ Trochospongilla.

   I. Rotules of the gemmule-spicules equal
      or nearly so.
      A. Skeleton-spicules smooth, usually
         pointed                             _latouchiana_, p. 115.
      B. Skeleton-spicules spiny, blunt      _phillottiana_, p. 117.
  II. Upper rotule of the gemmule-spicules
      distinctly smaller than the lower.
      Skeleton-spicules spiny, pointed       _pennsylvanica_, p. 118.


18. Trochospongilla latouchiana*, _Annandale_.

     _Trochospongilla latouchiana_, Annandale, J. Asiat. Soc.
     Bengal, 1907, p. 21, fig. 5.

     _Trochospongilla latouchiana_, _id._, Rec. Ind. Mus. ii, p.
     157 (1908).

     _Trochospongilla leidyi_, _id._ (_nec_ Bowerbank), _ibid._
     iii, p. 103 (1909).

[Illustration: Fig. 24.--_Trochospongilla latouchiana._

Vertical section of part of skeleton with gemmules _in situ_, × 30; also
a single gemmule, × 70. (From Calcutta).]

_Sponge_ forming cushion-shaped masses rarely more than a few
centimetres in diameter or thickness and of a brown or yellow colour,
hard but rather brittle; surface evenly rounded, minutely hispid; oscula
inconspicuous, small, circular, depressed, very few in number; external
membrane adhering closely to the parenchyma; a chitinous membrane at the
base of the sponge. Larger sponges divided into several layers by
similar membranes.

_Skeleton_ dense, forming a close reticulation; radiating fibres slender
but quite distinct, running up right through the sponge, crossed at
frequent intervals by single spicules or groups of spicules.

_Spicules._ Skeleton-spicules smooth, about twenty times as long as the
greatest transverse diameter, as a rule sharply pointed; smooth
amphistrongyli, which are often inflated in the middle, sometimes mixed
with them but never in large numbers. No flesh-spicules.
Gemmule-spicules with the rotulæ circular or slightly asymmetrical, flat
or nearly flat, marked with a distinct double circle as seen from above,
sometimes not quite equal; the shaft not projecting beyond them; the
diameter of the rotule 4-1/2 to 5 times that of the shaft, which is
about 2-2/3 times as long as broad.

_Gemmules_ small (0.2 × 0.18 mm.), as a rule very numerous and scattered
throughout the sponge, flask-shaped, clothed when mature with a thin
microcell coat in which the birotulates are arranged with overlapping
rotulæ, their outer rotulæ level with the surface; foraminal aperture
circular, situated on an eminence.


  _Average Measurements._

  Diameter of gemmule                0.2 × 0.18 mm.
  Length of skeleton-spicule               0.28  "
  Length of birotulate-spicule             0.175 "
  Diameter of rotula                       0.02  "

_T. latouchiana_ is closely related to _T. leidyi_ (Bowerbank) from N.
America, but is distinguished by its much more slender
skeleton-spicules, by the fact that the gemmules are not enclosed in
cages of megascleres or confined to the base of the sponge, and by
differences in the structure of the skeleton.

TYPE in the Indian Museum.

GEOGRAPHICAL DISTRIBUTION.--Lower Bengal and Lower Burma.
_Localities_:--BENGAL, Calcutta and neighbourhood (_Annandale_): BURMA,
Kawkareik, Amherst district, Tenasserim (_Annandale_).

BIOLOGY.--This species, which is common in the Museum tank, Calcutta, is
apparently one of those that can grow at any time of year, provided that
it is well covered with water. Like _T. leidyi_ it is capable of
producing fresh layers of living sponge on the top of old ones, from
which they are separated by a chitinous membrane. These layers are not,
however, necessarily produced in different seasons, for it is often
clear from the nature of the object to which the sponge is attached that
they must all have been produced in a short space of time. What appears
to happen in most cases is this:--A young sponge grows on a brick, the
stem of a reed or some other object at or near the edge of a pond, the
water in which commences to dry up. As the sponge becomes desiccated its
cells perish. Its gemmules are, however, retained in the close-meshed
skeleton, which persists without change of form. A heavy shower of rain
then falls, and the water rises again over the dried sponge. The
gemmules germinate immediately and their contents spread out over the
old skeleton, secrete a chitinous membrane and begin to build up a new
sponge. The process may be repeated several times at the change of the
seasons or even during the hot weather, or after a "break in the rains."
If, however, the dried sponge remains exposed to wind and rain for more
than a few months, it begins to disintegrate and its gemmules are
carried away to other places. Owing to their thin pneumatic coat and
relatively heavy spicules they are not very buoyant. Even in the most
favourable circumstances the sponge of _T. latouchiana_ never forms
sheets of great area. In spite of its rapid growth it is frequently
overgrown by _Spongilla carteri_.


19. Trochospongilla phillottiana*, _Annandale_.

     _Trochospongilla phillottiana_, Annandale, J. Asiat. Soc.
     Bengal, 1907, p. 22, fig. 6.

     _Trochospongilla phillottiana_, _id._, Rec. Ind. Mus. i, p.
     269 (1907).

     _Trochospongilla phillottiana_, _id._, _ibid._ ii, p. 157
     (1908).

_Sponge_ hard but friable, forming sheets or patches often of great
extent but never more than about 5 mm. thick; the surface minutely
hispid, flat; colour pale yellow, the golden-yellow gemmules shining
through the sponge in a very conspicuous manner; oscula inconspicuous;
external membrane adherent; no basal chitinous membrane.

_Skeleton_ dense but by no means strong; the reticulation close but
produced mainly by single spicules, which form triangular meshes;
radiating fibres never very distinct, only persisting for a short
distance in a vertical direction; each gemmule enclosed in an open,
irregular cage of skeleton-spicules.

_Spicules._ Skeleton-spicules short, slender, blunt, more or less
regularly and strongly spiny, straight or feebly curved. No
flesh-spicules. Gemmule-spicules with the rotulæ circular, very wide as
compared with the shaft, concave on the surface, with the shaft
projecting as an umbo on the surface; the lower rotula often a little
larger than the upper.

_Gemmules_ numerous, situated at the base of the sponge in irregular,
one-layered patches, small (0.32 × 0.264 mm.), of a brilliant golden
colour, distinctly wider than high, with a single aperture situated on
an eminence on the apex, each clothed (when mature) with a pneumatic
coat that contains relatively large but irregular air-spaces among which
the spicules stand with the rotulæ overlapping alternately, a
funnel-shaped pit in the coat descending from the surface to the upper
rotula of each of them; the surface of the gemmule covered with
irregular projections.

  Diameter of gemmule          0.32 × 0.264 mm.
  Length of skeleton-spicule          0.177  "
  Length of gemmule-spicule           0.015  "
  Diameter of rotule                  0.022  "

This species appears to be related to _T. pennsylvanica_, from which it
differs mainly in the form of its gemmule-spicules and the structure of
its gemmule. My original description was based on specimens in which the
gemmule-spicules were not quite mature.

TYPE in the Indian Museum.

GEOGRAPHICAL DISTRIBUTION.--Lower Bengal and Lower Burma.
_Localities_:--BENGAL, Calcutta (_Annandale_): BURMA, jungle pool near
Kawkareik, Amherst district, Tenasserim (_Annandale_).

BIOLOGY.--This species covers a brick wall at the edge of the Museum
tank in Calcutta every year during the "rains." In the cold weather the
wall is left dry, but it is usually submerged to a depth of several feet
before the middle of July. It is then rapidly covered by a thin layer of
the sponge, which dies down as soon as the water begins to sink when the
"rains" are over. For some months the gemmules adhere to the wall on
account of the cage of spicules in which each of them is enclosed, but
long before the water rises again the cages disintegrate and the
gemmules are set free. Many of them fall or are carried by the wind into
the water, on the surface of which, owing to their thick pneumatic coat,
they float buoyantly. Others are lodged in cavities in the wall. On the
water the force of gravity attracts them to one another and to the edge
of the pond, and as the water rises they are carried against the wall
and germinate. In thick jungle at the base of the Dawna Hills near
Kawkareik[AI] in the interior of Tenasserim, I found the leaves of
shrubs which grew round a small pool, covered with little dry patches of
the sponge, which had evidently grown upon them when the bushes were
submerged. This was in March, during an unusually severe drought.

     [Footnote AI: This locality is often referred to in
     zoological literature as Kawkare_et_ or Kawkari_t_, or even
     K_o_kari_t_.]


20. Trochospongilla pennsylvanica* (_Potts_).

     _Tubella pennsylvanica_, Potts, P. Ac. Philad. 1882, p. 14.

     _Tubella pennsylvanica_, _id._, _ibid._ 1887, p. 251, pl.
     vi, fig. 2, pl. xii, figs. 1-3.

     _Tubella pennsylvanica_, Mackay, Trans. Roy. Soc. Canada,
     1889, Sec. iv, p. 95.

     _Tubella pennsylvanica_, Hanitsch, Nature, li, p. 511
     (1895).

     _Tubella pennsylvanica_, Weltner, Arch. Naturg. lxi (i), p.
     128 (1895).

     _Tubella pennsylvanica_, Hanitsch, Irish Natural. iv, p. 129
     (1895).

     _Tubella pennsylvanica_, Annandale, J. Linn. Soc., Zool.,
     xxx, p. 248 (1908).

     _Tubella pennsylvanica_, _id._, Rec. Ind. Mus. iii, p. 102
     (1909).

     _Tubella_ _pennsylvanica_, _id._, P. U.S. Mus. xxxvii, p.
     403, fig. 2 (1909).

_Sponge_ soft, fragile, forming small cushion-shaped masses, grey or
green; oscula few in number, often raised on sloping eminences
surrounded by radiating furrows below the external membrane; external
membrane adhering to the parenchyma.

_Skeleton_ close, almost structureless. "Surface of mature specimens
often found covered with parallel skeleton spicules, not yet arranged to
form cell-like interspaces" (_Potts_).

_Spicules._ Skeleton-spicules slender, cylindrical, almost straight,
sharp or blunt, minutely, uniformly or almost uniformly spined; spines
sometimes absent at the tips. No flesh-spicules. Gemmule-spicules with
the lower rotula invariably larger than the upper; both rotulæ flat or
somewhat sinuous in profile, usually circular but sometimes asymmetrical
or subquadrate in outline, varying considerably in size.

_Gemmules_ small, numerous or altogether absent, covered with a granular
pneumatic coat of variable thickness; the rotulæ of the gemmule-spicules
overlapping and sometimes projecting out of the granular coat.

The measurements of the spicules and gemmules of an Indian specimen and
of one from Lehigh Gap, Pennsylvania, are given for comparison:--

                                   Travancore.          Pennsylvania.
  Length of skeleton-spicules    0.189-0.242 mm.        0.16-0.21 mm.
                              (average 0.205 mm.)   (average 0.195 mm.)
  Breadth      "        "       0.0084-0.0155 mm.        0.0084 mm.
  Length of birotulate                 0.0126  "         0.0099  "
  Diameter of upper rotula             0.0084  "         0.0084  "
       "      lower   "                0.0169  "         0.0168  "
       "      gemmule                  0.243-0.348 mm.   0.174-0.435 mm.

The spicules of the Travancore specimen are, therefore, a trifle larger
than those of the American one, but the proportions are closely similar.

The difference between the gemmule-spicules of this species and those of
such a form as _T. phillottiana_ is merely one of degree and can hardly
be regarded as a sufficient justification for placing the two species in
different genera. If, as I have proposed, we confine the generic name
_Tubella_ to those species in which the gemmule-spicules are really like
"little trumpets," the arrangement is a much more natural one, for these
species have much in common apart from the gemmule-spicules. _T.
pennsylvanica_ does not appear to be very closely related to any other
known species except _T. phillottiana_.

TYPE in the U.S. National Museum, from which specimens that appear to be
co-types have been sent to the Indian Museum.

GEOGRAPHICAL DISTRIBUTION.--Very wide and apparently discontinuous:--N.
America (widely distributed), Ireland (_Hanitsch_), Hebrides of Scotland
(_Annandale_), Travancore, S. India (_Annandale_). The only Indian
locality whence I have obtained specimens is Shasthancottah Lake near
Quilon in Travancore.

BIOLOGY.--In Shasthancottah Lake _T. pennsylvanica_ is found on the
roots of water-plants that are matted together to form floating islands.
It appears to avoid light and can only be obtained from roots that have
been pulled out from under the islands. In Scotland I found it on the
lower surface of stones near the edge of Loch Baa, Isle of Mull. In such
circumstances the sponge is of a greyish colour, but specimens of the
variety _minima_ taken by Potts on rocks and boulders in Bear Lake,
Pennsylvania, were of a bright green.

Sponges taken in Travancore in November were full of gemmules; in my
Scottish specimens (taken in October) I can find no traces of these
bodies, but embryos are numerous.


Genus 6. TUBELLA, _Carter_.

     _Tubella_, Carter, Ann. Nat. Hist. (5) vii, p. 96 (1881).

     _Tubella_, Potts (_partim_), P. Ac. Philad. 1887, p. 248.

     _Tubella_, Weltner (_partim_), Arch. Naturg. lxi (i), p. 128
     (1895).

TYPE, _Spongilla paulula_, Bowerbank.

This genus is distinguished from _Ephydatia_ and _Trochospongilla_ by
the fact that the two ends of the gemmule-spicules are unlike not only
in size but also in form. It sometimes happens that this unlikeness is
not so marked in some spicules as in others, but in some if not in all
the upper end of the shaft (that is to say the end furthest removed from
the inner coat of the gemmule in the natural position) is reduced to a
rounded knob, while the lower end expands into a flat transverse disk
with a smooth or denticulated edge. The spicule thus resembles a little
trumpet resting on its mouth. The shaft of the spicule is generally
slender and of considerable length. The skeleton of the sponge is as a
rule distinctly reticulate and often hard; the skeleton-spicules are
either slender or stout and sometimes change considerably in proportions
and outline as they approach the gemmules.

GEOGRAPHICAL DISTRIBUTION.--The genus is widely distributed in the
tropics of both Hemispheres, its headquarters apparently being in S.
America; but it is nowhere rich in species. Only two are known from the
Oriental Region, namely _T. vesparium_* from Borneo, and _T.
vesparioides_* from Burma.


21. Tubella vesparioides*, _Annandale_. (Plate II, fig. 4.)

     _Tubella vesparioides_, Annandale, Rec. Ind. Mus. ii, p. 157
     (1908).

_Sponge_ forming rather thick sheets of considerable size, hard but
brittle, almost black in colour; oscula inconspicuous; external membrane
supported on a reticulate horizontal skeleton.

_Skeleton._ The surface covered with a network of stout spicule-fibres,
the interstices of which are more or less deeply sunk, with sharp fibres
projecting vertically upwards at the nodes; the whole mass pervaded by a
similar network, which is composed of a considerable number of spicules
lying parallel to one another, overlapping at the ends and bound
together by a profuse secretion of spongin.

[Illustration: Fig. 25.--Spicules of _Tubella vesparioides_ (from type
specimen). × 240.]

_Spicules._ Skeleton-spicules slender, smooth, amphioxous, bent in a
wide arc or, not infrequently, at an angle. No true flesh-spicules.
Gemmule-spicules terminating above in a rounded, knob-like structure and
below in a relatively broad, flat rotula, which is very deeply and
irregularly indented round the edge when mature, the spicules at an
earlier stage of development having the form of a sharp pin with a round
head; shaft of adult spicules projecting slightly below the rotula,
long, slender, generally armed with a few stout conical spines, which
stand out at right angles to it.

_Gemmules_ numerous throughout the sponge, spherical, provided with a
short, straight foraminal tubule, surrounded by one row of spicules,
which are embedded in a rather thin granular coat.

  Average length of skeleton-spicule          0.316 mm.
    "     breadth of skeleton-spicule         0.0135 "
    "     length of gemmule-spicule           0.046  "
    "     diameter of rotula                  0.0162 "
    "         "       gemmule                 0.446  "

This sponge is closely related to _Tubella vesparium_ (v. Martens) from
Borneo, from which it may be distinguished by its smooth
skeleton-spicules and the deeply indented disk of its gemmule-spicules.
The skeleton-fibres are also rather less stout. By the kindness of Dr.
Weltner, I have been able to compare types of the two species.

TYPE in the Indian Museum.

HABITAT.--Taken at the edge of the Kanghyi ("great pond") at Mudon near
Moulmein in the Amherst district of Tenasserim. The specimens were
obtained in March in a dry state and had grown on logs and branches
which had evidently been submerged earlier in the year. The name
_vesparium_ given to the allied species on account of its resemblance to
a wasps' nest applies with almost equal force to this Burmese form.


Genus 7. CORVOSPONGILLA, nov.

TYPE[AJ], _Spongilla loricata_, Weltner.

     [Footnote AJ: Potts's _Spongilla novæ-terræ_ from
     Newfoundland and N. America cannot belong to this genus
     although it has similar flesh-spicules, for, as Weltner has
     pointed out (_op. cit. supra_ p. 126), the gemmule-spicules
     are abortive rotulæ. This is shown very clearly in the
     figure published by Petr (Rozp. Ceske Ak. Praze, Trída, ii,
     pl. ii, figs. 27, 28, 1899), who assigns the species to
     _Heteromeyenia_. Weltner places it in _Ephydatia_, and it
     seems to be a connecting link between the two genera. It has
     been suggested that it is a hybrid (Traxler, Termes.
     Fuzetek, xxi, p. 314, 1898).]

Spongillidæ in which the gemmule-spicules are without a trace of rotulæ
and the flesh-spicules have slender cylindrical shafts that bear at or
near either end a circle of strong recurved spines. The gemmule-spicules
are usually stout and sausage-shaped, and the gemmules resemble those of
_Stratospongilla_ in structure. The skeleton is strong and the
skeleton-spicules stout, both resembling those of the "genus"
_Potamolepis_, Marshall.

As in all other genera of Spongillidæ the structure of the skeleton is
somewhat variable, the spicule-fibres of which it is composed being much
more distinct in some species than in others. The skeleton-spicules are
often very numerous and in some cases the skeleton is so compact and
rigid that the sponge may be described as stony. The flesh-spicules
closely resemble the gemmule-spicules of some species of _Ephydatia_ and
_Heteromeyenia_.

GEOGRAPHICAL DISTRIBUTION.--The species of this genus are probably
confined to Africa (whence at least four are known) and the Oriental
Region. One has been recorded from Burma and another from the Bombay
Presidency.


  _Key to the Indian Species of_ Corvospongilla.

  I. Gemmule with two layers of gemmule-spicules;
  those of the inner layer not
  markedly smaller than those of the outer.       _burmanica_, p. 123.

  II. Gemmule with two layers of gemmule-spicules,
  the outer of which contains
  spicules of much greater size than the
  inner.                                          _lapidosa_, p. 124.


22. Corvospongilla burmanica* (_Kirkpatrick_). (Plate II, fig. 5.)

     _Spongilla loricata_ var. _burmanica_, Kirkpatrick, Rec.
     Ind. Mus. ii, p. 97, pl. ix (1908).

_Sponge_ forming a shallow sheet, hard, not very strong, of a pale
brownish colour; the surface irregularly spiny; the oscula small but
conspicuous, circular, raised on little turret-like eminences; the
external membrane adhering closely to the sponge.

_Skeleton_ dense but by no means regular; the network composed largely
of single spines; thick radiating fibres distinguishable in the upper
part of the sponge.

_Spicules._ Skeleton-spicules smooth, not very stout, amphistrongylous,
occasionally a little swollen at the ends, often with one or more
fusiform swellings, measuring on an average about 0.27 × 0.0195 mm.
Flesh-spicules with distinct rotules, the recurved spines numbering 4 to
6, measuring about 1/7 the length of the spicules; the shaft by no means
strongly curved; their length from 0.03-0.045 mm. Gemmule-spicules
amphioxous, as a rule distinctly curved, sometimes swollen at the ends,
covered regularly but somewhat sparsely with fine spines, not measuring
more than 0.49 × 0.078 mm.

_Gemmules_ strongly adherent, arranged in small groups, either single or
double; when single spherical, when double oval; each gemmule or pair of
gemmules covered by two layers of gemmule-spicules bound together in
chitinous substance; the inner layer on the inner coat of the gemmule,
the outer one separated from it by a space and in contact with the outer
cage of skeleton-spicules; the size of the gemmule-spicules variable in
both layers; external to the outer layer a dense cage of
skeleton-spicules; foraminal tubule short, cylindrical.

This sponge is closely related to _S. loricata_, Weltner, of which
Kirkpatrick regards it as a variety. "The main difference," he writes,
"between the typical African form and the Burmese variety consists in
the former having much larger microstrongyles (83 × 15.7 µ [0.83 × 0.157
mm.]) with larger and coarser spines;... Judging from Prof. Weltner's
sections of gemmules, these bodies lack the definite outer shell of
smooth macrostrongyles [blunt skeleton-spicules], though this may not
improbably be due to the breaking down and removal of this layer. A
further difference consists in the presence, in the African specimen, of
slender, finely spined strongyles [amphistrongyli], these being absent
in the Burmese form, though perhaps this fact is not of much
importance."

TYPE in the British Museum; a piece in the Indian Museum.

HABITAT.--Myitkyo, head of the Pegu-Sittang canal, Lower Burma (_E. W.
Oates_).

BIOLOGY.--The sponge had grown over a sheet of the polyzoon _Hislopia
lacustris_, Carter (see p. 204), remains of which can be detected on its
lower surface.

"Mr. E. W. Oates, who collected and presented the sponge, writes that
the specimen was found encrusting the vertical and horizontal surfaces
of the bottom beam of a lock gate, where it covered an area of six
square feet. The beam had been tarred several times before the sponge
was discovered. The portion of the gate on which the sponge was growing
was submerged from November to May for eight hours a day at spring
tides, but was entirely dry during the six days of neap tides. From May
to October it was constantly submerged. The sponge was found in April.
Although the canal is subject to the tides, the water at the lock is
always fresh. The colour of the sponge during life was the same as in
its present condition."


23. Corvospongilla lapidosa* (_Annandale_).

     _Spongilla lapidosa_ Annandale, Rec. Ind. Mus. ii, pp. 25,
     26, figs. 3, 4, 5 (1908).

The _sponge_ forms a thin but extremely hard and resistant crust the
surface of which is either level, slightly concave, or distinctly
corrugated; occasional groups of spicules project from it, but their
arrangement is neither so regular nor so close as is the case in _C.
burmanica_. The dermal membrane adheres closely to the sponge. The
oscula are small; some of them are raised above the general surface but
not on regular turret-shaped eminences. The colour is grey or black.
There is a thick chitinous membrane at the base of the sponge.

[Illustration: Fig. 26.--Spicules of _Corvospongilla lapidosa_ (from
type specimen), × 240.]

The _skeleton_ is extremely dense owing to the large number of spicules
it contains, but almost structureless; broad vertical groups of spicules
occur but lack spongin and only traverse a small part of the thickness
of the sponge; their position is irregular. The firmness of the skeleton
is due almost entirely to the interlocking of individual spicules. At
the base of the sponge the direction of a large proportion of the
spicules is horizontal or nearly horizontal, the number arranged
vertically being much greater in the upper part.

_Spicules._ The skeleton-spicules are sausage-shaped and often a little
swollen at the ends or constricted in the middle. A large proportion are
twisted or bent in various ways, and a few bear irregular projections or
swellings. The majority, however, are quite smooth. Among them a few
more or less slender, smooth amphioxi occur, but these are probably
immature spicules. The length and curvature of the amphistrongyli varies
considerably, but the average measurements are about 0.28 × 0.024 mm.
The flesh-spicules also vary greatly in length and in the degree to
which their shafts are curved. At first sight it seems to be possible to
separate them into two categories, one in which the shaft is about 0.159
mm. long, and another in which it is only 0.05 mm. or even less; and
groups of birotulates of approximately the same length often occur in
the interstices of the skeleton. Spicules of all intermediate lengths
can, however, be found. The average diameter of the shaft is 0.0026 mm.
and of the rotula 0.0106 mm., and the rotula consists of from 6 to 8
spines. The gemmule-spicules vary greatly in size, the longest measuring
about 0.08 × 0.014 and the smallest about 0.034 × 0.007 or even less.
There appears to be in their case an even more distinct separation as
regards size than there is in that of the flesh-spicules; but here again
intermediate forms occur. They are all stout, more or less blunt, and
more or less regularly covered with very short spines; most of them are
distinctly curved, but some are quite straight.

_Gemmules._ The gemmules are firmly adherent to the support of the
sponge, at the base of which they are congregated in groups of four or
more. They vary considerably in size and shape, many of them being
asymmetrical and some elongate and sausage-shaped. The latter consist of
single gemmules and not of a pair in one case. Extreme forms measure
0.38 × 0.29 and 0.55 × 0.25. Each gemmule is covered with a thick
chitinous membrane in close contact with its wall and surrounding it
completely. This membrane is full of spicules arranged as in a mosaic;
most or all of them belong to the smaller type, and as a rule they are
fairly uniform in size. Separated from this layer by a considerable
interval is another layer of spicules embedded in a chitinous membrane
which is in continuity with the basal membrane of the sponge. The
spicules in this membrane mostly belong to the larger type and are very
variable in size; mingled with them are often a certain number of
birotulate flesh-spicules. The membrane is in close contact with a dense
cage of skeleton-spicules arranged parallel to it and bound together by
chitinous substance. The walls of this cage, when they are in contact
with those of the cages of other gemmules, are coterminous with them.
There is a single depressed aperture in the gemmules, as a rule situated
on one of the longer sides.

This sponge is distinguished from _C. burmanica_ not only by differences
in external form, in the proportions of the spicules and the structure
of the skeleton, but also by the peculiar nature of the armature of the
gemmule. The fact that birotulate spicules are often found in close
association with them, is particularly noteworthy.

TYPE in the Indian Museum.

GEOGRAPHICAL DISTRIBUTION.--This sponge has only been found in the
Western Ghats of the Bombay Presidency. _Localities_:--Igatpuri Lake and
the R. Godaveri at Nasik.

BIOLOGY.--There is a remarkable difference in external form between the
specimens taken in Igatpuri and those from Nasik, and this difference is
apparently due directly to environment. In the lake, the waters of which
are free from mud, the sponges were growing on the lower surface of
stones near the edge. They formed small crusts not more than about 5 cm.
(2 inches) in diameter and of a pale greyish colour. Their surface was
flat or undulated gently, except round the oscula where it was raised
into sharply conical eminences with furrowed sides. The specimens from
Nasik, which is about 30 miles from Igatpuri, were attached, together
with specimens of _Spongilla cinerea_ and _S. indica_, to the sides of a
stone conduit full of very muddy running water. They were black in
colour, formed broad sheets and were markedly corrugated on the surface.
Their oscula were not raised on conical eminences and were altogether
most inconspicuous. The skeleton was also harder than that of sponges
from the lake.

In the lake _C. lapidosa_ was accompanied by the gemmules of _Spongilla
bombayensis_, but it is interesting that whereas the latter sponge was
entirely in a resting condition, the former was in full vegetative
vigour, a fact which proves, if proof were necessary, that the similar
conditions of environment do not invariably have the same effect on
different species of Spongillidæ.


  APPENDIX TO PART I.

  FORM OF UNCERTAIN POSITION.

  (Plate I, fig. 4.)

On more than one occasion I have found in my aquarium in Calcutta small
sponges of a peculiar type which I am unable to refer with certainty to
any of the species described above. Fig. 4, pl. I, represents one of
these sponges. They are never more than about a quarter of an inch in
diameter and never possess more than one osculum. They are
cushion-shaped, colourless and soft. The skeleton-spicules are smooth,
sharply pointed, moderately slender and relatively large. They are
arranged in definite vertical groups, which project through the dermal
membrane, and in irregular transverse formation. Small spherical
gemmules are present but have only a thin chitinous covering without
spicules or foramen.

These sponges probably represent an abnormal form of some well-known
species, possibly of _Spongilla carteri_. I have seen nothing like them
in natural conditions.




  PART II.

  FRESHWATER POLYPS

  (HYDRIDA).




INTRODUCTION TO PART II.


I.

THE PHYLUM COELENTERATA AND THE CLASS HYDROZOA.


The second of the great groups or phyla into which the metazoa are
divided is the Coelenterata, in which are included most of the animals
commonly known as zoophytes, and also the corals, sea-anemones and
jelly-fish. These animals are distinguished from the sponges on the one
hand and from the worms, molluscs, arthropods, vertebrates, etc., on the
other by possessing a central cavity (the coelenteron or "hollow
inside") the walls of which are the walls of the body and consist of
_two_ layers of cells separated by a structureless, or apparently
structureless, jelly. This cavity has as a main function that of a
digestive cavity.

An ideally simple coelenterate would not differ much in general
appearance from an olynthus (p. 27), but it would have no pores in the
body-wall and its upper orifice would probably be surrounded by
prolongations of the body-wall in the form of tentacles. There would be
no collar-cells, and the cells of the body generally would have a much
more fixed and definite position and more regular functions than those
of any sponge. The most characteristic of them would be the so-called
cnidoblasts. Each of these cells contains a capsule[AK] from which a
long thread-like body can be suddenly uncoiled and shot out.

     [Footnote AK: Similar capsules are found in the tissues of
     certain worms and molluscs, but there is the strongest
     evidence that these animals, which habitually devour
     coelenterates, are able to swallow the capsules uninjured
     and to use them as weapons of defence (see Martin, Q. J.
     Micro. Sci. London, lii, p. 261, 1908, and Grosvenor, Proc.
     Roy. Soc. London, lxxii, p. 462, 1903). The "trichocysts" of
     certain protozoa bear a certain resemblance to the
     nettle-cells of coelenterates and probably have similar
     functions.]

The simplest in structure of the coelenterates are those that constitute
the class Hydrozoa. In this class the primitive central cavity is not
divided up by muscular partitions and there is no folding in of the
anterior part of the body to form an oesophagus or stomatodæum such as
is found in the sea-anemones and coral polyps. In many species and
genera the life-history is complex, illustrating what is called the
alternation of generations. That is to say, only alternate generations
attain sexual maturity, those that do so being produced as buds from a
sexless generation, which itself arises from the fertilized eggs of a
previous sexual generation. The sexual forms as a rule differ
considerably in structure from the sexless ones; many medusæ are the
sexual individuals in a life-cycle in which those of the sexless
generation are sedentary.

An excellent general account of the coelenterates will be found in the
Cambridge Natural History, vol. i (by Prof. Hickson).


STRUCTURE OF HYDRA.

_Hydra_, the freshwater polyp, is one of the simplest of the Hydrozoa
both as regards structure and as regards life-history. Indeed, it
differs little as regards structure from the ideally simple coelenterate
sketched in a former paragraph, while its descent is direct from one
polyp to another, every generation laying its own eggs[AL]. The animal
may be described as consisting of the following parts:--(1) an upright
(or potentially upright) column or body, (2) a circle of contractile
tentacles at the upper extremity of the column, (3) an oral disk or
peristome surrounding the mouth and surrounded by the tentacles, and (4)
a basal or aboral disk at the opposite extremity. The whole animal is
soft and naked. The column, when the animal is at rest, is almost
cylindrical in some forms but in others has the basal part distinctly
narrower than the upper part. It is highly contractile and when
contracted sometimes assumes an annulate appearance; but as a rule the
external surface is smooth.

     [Footnote AL: The statement is not strictly accurate as
     regards the Calcutta phase of _H. vulgaris_, for the summer
     brood apparently does not lay eggs but reproduces its
     species by means of buds only. This state of affairs,
     however, is probably an abnormality directly due to
     environment.]

The tentacles vary in number, but are never very numerous. They are
disposed in a single circle round the oral disk and are hollow, each
containing a prolongation of the central cavity of the column. Like the
column but to an even greater degree they are contractile, and in some
forms they are capable of great elongation. They cannot seize any object
between them, but are able to move in all directions.

The disk that surrounds the mouth, which is a circular aperture, is
narrow and can to some extent assume the form of a conical proboscis,
although this feature is never so marked as it is in some hydroids. The
basal disk is even narrower and is not splayed out round the edges.

[Illustration: Fig. 27.--Nettle-cells of _Hydra_.

A=capsules from nettle-cells of a single specimen of the summer phase of
_H. vulgaris_ from Calcutta, × 480: figures marked with a dash represent
capsules with barbed threads. B=a capsule with the thread discharged,
from the same specimen, × 480. C=capsule with barbed thread, from a
specimen of _H. oligactis_ from Lahore. D=undischarged nettle-cell of
_H. vulgaris_ from Europe (after Nussbaum, highly magnified).
E=discharged capsule of the same (after the same author).
_a_=cnidoblast; _b_=capsule; _c_=thread; _d_=cnidocil. Only the base of
the thread is shown in E.]

A section through the body-wall shows it to consist of the three typical
layers of the coelenterates, viz., (i) an outer cellular layer of
comparatively small cells, the ectoderm; (ii) an intermediate,
structureless or apparently structureless layer, the mesogloea or
"central jelly"; and (iii) an internal layer or endoderm consisting of
relatively large cells. The cells of the ectoderm are not homogeneous.
Some of them possess at their base narrow and highly contractile
prolongations that exercise the functions of muscles. Others are
gland-cells and secrete mucus; others have round their margins delicate
ramifying prolongations and act as nerve-cells. Sense-cells, each of
which bears on its external surface a minute projecting bristle, are
found in connection with the nerve-cells, and also nettle-cells of more
than one type.

The mesogloea is very thin.

The endoderm consists mainly of comparatively large cells with polygonal
bases which can be seen from the external surface of the column in
colourless individuals. Their inner surface is amoeboid and in certain
conditions bears one or more vibratile cilia or protoplasmic lashes.
Nettle-cells are occasionally found in the endoderm, but apparently do
not originate in this layer.

The walls of the tentacles do not differ in general structure from those
of the column, but the cells of the endoderm are smaller and the
nematocysts of the ectoderm more numerous, and there are other minor
differences.

A more detailed account of the anatomy of _Hydra_ will be found in any
biological text-book, for instance in Parker's Elementary Biology; but
it is necessary here to say something more as regards the nettle-cells,
which are of great biological and systematic importance.

A nettle-cell of the most perfect type and the structures necessary to
it consist of the following parts:--

     (1) A true cell (the cnidoblast), which contains--
     (2) a delicate capsule full of liquid;
     (3) a long thread coiled up in the capsule; and
     (4) a cnidocil or sensory bristle, which projects from the
         external surface of the cnidoblast.

A nerve-cell is associated with each cnidoblast.

In _Hydra_ the nettle-cells are of two distinct types, in one of which
the thread is barbed at the base, whereas in the other it is simple.
Both types have often two or more varieties and intermediate forms
occur, but generally speaking the capsules with simple threads are much
smaller than those with barbed ones. The arrangement of the nettle-cells
is not the same in all species of _Hydra_, but as a rule they are much
more numerous in the tentacles than elsewhere on the body, each large
cell being surrounded by several small ones. The latter are always much
more numerous than the former.


CAPTURE AND INGESTION OF PREY: DIGESTION.

The usual food of _Hydra_ consists of small insect larvæ, worms, and
crustacea, but the eggs of fish are also devoured. The method in which
prey is captured and ingested has been much disputed, but the following
facts appear to be well established.

If a small animal comes in contact with the tentacles of the polyp, it
instantly becomes paralysed. If it adheres to the tentacle, it perishes;
but if, as is often the case, it does not do so, it soon recovers the
power of movement. Animals which do not adhere are generally those (such
as ostracod crustacea) which have a hard integument without weak spots.
Nematocysts of both kinds shoot out their threads against prey with
considerable violence, the discharge being effected, apparently in
response to a chemical stimulus, by the sudden uncoiling of the thread
and its eversion from the capsule. Apparently the two kinds of threads
have different functions to perform, for whereas there is no doubt that
the barbed threads penetrate the more tender parts of the body against
which they are hurled, there is evidence that the simple threads do not
do so but wrap themselves round the more slender parts. Nussbaum (Arch.
mikr. Anat. xxix, pl. xx, fig. 108) figures the tail of a _Cyclops_
attacked by _Hydra vulgaris_ and shows several simple threads wrapped
round the hairs and a single barbed thread that has penetrated the
integument. Sometimes the cyst adheres to the thread and remains
attached to its cnidoblast and to the polyp, but sometimes the thread
breaks loose. Owing to the large mass of threads that sometimes
congregate at the weaker spots in the external covering of an animal
attacked (_e. g._, at the little sensory pits in the integument of the
dorsal surface of certain water-mites) it is often difficult to trace
out the whole length of any one thread, and as a thread still attached
to its capsule is frequently buried in the body of the prey, right up to
the barbs, while another thread that has broken loose from its capsule
appears immediately behind the fixed one, it seems as though the barbs,
which naturally point towards the capsule, had become reversed. This
appearance, however, is deceptive. The barbs are probably connected with
the discharge of the thread and do not function at all in the same way
as those on a spear- or arrow-head, never penetrating the object against
which the projectile is hurled. Indeed, their position as regards the
thread resembles that of the feathers on the shaft of an arrow rather
than that of the barb of the head.

Adhesion between the tentacles and the prey is effected partly by the
gummy secretion of the glands of the ectoderm, which is perhaps
poisonous as well as adhesive, and partly by the threads. Once the prey
is fast and has ceased to struggle, it is brought to the mouth, which
opens wide to receive it, by the contraction and the contortions of the
tentacles, the column, and the peristome. At the same time a mass of
transparent mucus from the gastral cavity envelops it and assists in
dragging it in. There is some dispute as to the part played by the
tentacles in conveying food into the mouth. My own observations lead me
to think that, at any rate so far as _H. vulgaris_ is concerned, they do
not push it in, but sometimes in their contortions they even enter the
cavity accidentally.

When the food has once been engulfed some digestive fluid is apparently
poured out upon it. In _H. vulgaris_ it is retained in the upper part of
the cavity and the soluble parts are here dissolved out, the insoluble
parts such as the chitin of insect larvæ or crustacea being ejected from
the mouth. Digestion is, however, to a considerable extent
intracellular, for the cells of the endoderm have the power of thrusting
out from their surface lobular masses of their cell-substance in which
minute nutritive particles are enveloped and dissolved. The movements of
the cilia which can also be thrust out from and retracted into these
cells, keep the food in the gastral cavity in motion and probably turn
it round so as to expose all parts in turn to digestive action. Complete
digestion, at any rate in the Calcutta form, takes several days to
accomplish, and after the process is finished a flocculent mass of
colourless excreta is emitted from the mouth.


COLOUR.

In _Hydra viridis_, a species that has not yet been found in India, the
green colour is due to the presence in the cells of green corpuscles
which closely resemble those of the cells of certain freshwater sponges.
They represent a stage in the life-cycle of _Chlorella vulgaris_,
Beyerinck[AM], an alga which has been cultivated independently.

     [Footnote AM: Bot. Zeitung, xlviii (1890): see p. 49, _antea_.]

In other species of the genus colour is largely dependent on food,
although minute corpuscles of a _dark_ green shade are sometimes found
in the cells of _H. oligactis_. In the Calcutta phase of _H. vulgaris_
colour is due entirely to amorphous particles situated mainly in the
cells of the endoderm. If the polyp is starved or exposed to a high
temperature, these particles disappear and it becomes practically
colourless. They probably form, therefore, some kind of food-reserve,
and it is noteworthy that a polyp kept in the unnatural conditions that
prevail in a small aquarium invariably becomes pale, and that its
excreta are not white and flocculent but contain dark granules
apparently identical with those found in the cells of coloured
individuals (p. 154).

Berninger[AN] has just published observations on the effect of
long-continued starvation on _Hydra_ carried out in Germany. He finds
that the tentacles, mouth, and central jelly disappear, and that a
closed "bladder" consisting of two cellular layers remains; but, to
judge from his figures, the colour does not disappear in these
circumstances.

     [Footnote AN: Zool. Anz. xxxvi, pp. 271-279, figs., Oct.
     1910.]


BEHAVIOUR.

_Hydra viridis_ is a more sluggish animal than the other species of its
genus and does not possess the same power of elongating its column and
tentacles. It is, nevertheless, obliged to feed more frequently. Wagner
(Quart. J. Micr. Sci. xlviii, p. 586, 1905) found it impossible to use
this species in his physiological experiments because it died of
starvation more rapidly than other forms. This fact is interesting in
view of the theory that the green corpuscles in the cells of _H.
viridis_ elaborate nutritive substances for its benefit. _H. vulgaris_,
at any rate in Calcutta, does not ordinarily capture prey more often
than about once in three days.

All _Hydræ_ (except possibly the problematical _H. rubra_ of Roux, p.
160) spend the greater part of their time attached by the basal disk to
some solid object, but, especially in early life, _H. vulgaris_ is often
found floating free in the water, and all the species possess powers of
progression. They do not, however, all move in the same way. _H.
viridis_ progresses by "looping" like a geometrid caterpillar. During
each forward movement the column is arched downwards so that the
peristome is in contact with the surface along which the animal is
moving. The basal disk is then detached and the column is twisted round
until the basal disk again comes in contact with the surface at a point
some distance in advance of its previous point of attachment. The
manoeuvre is then repeated. _H. vulgaris_, when about to move, bends
down its column so that it lies almost prone, stretches out its
tentacles, which adhere near the tips to the surface (p. 153), detaches
its basal disk, and then contracts the tentacles. The column is dragged
forward, still lying almost prone, the basal disk is bent downwards and
again attached, and the whole movement is repeated. Probably _H.
oligactis_ moves in the same way.

When _H. viridis_ is at rest the tentacles and column, according to
Wagner, exhibit rhythmical contractions in which those of the buds act
in sympathy with those of the parent. In _H. vulgaris_ no such movements
have been observed. This species, however, when it is waiting for prey
(p. 154) changes the direction of its tentacles about once in half an
hour.

All species of _Hydra_ react to chemical and physical stimuli by
contraction and by movements of the column and tentacles, but if the
stimuli are constantly repeated, they lose the power to some extent. All
species are attracted by light and move towards the point whence it
reaches them. _H. vulgaris_, however, at any rate in India, is more
strongly repelled by heat. Consequently, if it is placed in a glass
vessel of water, on one side of which the sun is shining directly, it
moves away from the source of the light[AO]. But if the vessel be
protected from the direct rays of the sun and only a subdued light falls
on one side of it, the polyp moves towards that side. No species of the
genus is able to move in a straight line. Wilson (Amer. Natural. xxv, p.
426, 1891) and Wagner (_op. cit. supra_) have published charts showing
the elaborately erratic course pursued by a polyp in moving from one
point to another and the effect of light as regards its movements.

     [Footnote AO: Mr. F. H. Gravely tells me that this is also
     the case as regards _H. viridis_ in England, at any rate if
     freshly captured specimens are placed overnight in a bottle
     in a window in such a position that the early morning
     sunlight falls upon one side of the bottle.]

If an individual of _H. vulgaris_ that contains half digested food in
its gastral cavity is violently removed from its natural surroundings
and placed in a glass of water, the column and tentacles contract
strongly for a few minutes. The body then becomes greatly elongated and
the tentacles moderately so; the tentacles writhe in all directions
(their tips being sometimes thrust into the mouth), and the food is
ejected.


REPRODUCTION.

Reproduction takes place in _Hydra_ (i) by means of buds, (ii) by means
of eggs, and (iii) occasionally by fission.


(a) _Sexual Reproduction._

The sexual organs consist of ovaries (female) and spermaries (male).
Sometimes the two kinds of organs are borne by the same individual
either simultaneously or in succession, but some individuals or races
appear to be exclusively of one sex. There is much evidence that in
unfavourable conditions the larger proportion of individuals develop
only male organs.

In temperate climates most forms of _Hydra_ breed at the approach of
winter, but starvation undoubtedly induces a precocious sexual activity,
and the same is probably the case as regards other unfavourable
conditions such as lack of oxygen in the water and either too high or
too low a temperature.

Downing states that in N. America (Chicago) _H. vulgaris_ breeds in
spring and sometimes as late as December; in Calcutta it has only been
found breeding in February and March. Except during the breeding-season
sexual organs are absent; they do not appear in the same position on the
column in all species.

The spermaries take the form of small mound-shaped projections on the
surface of the column. Each consists of a mass of sperm-mother cells, in
which the spermatozoa originate in large numbers. The spermatozoa
resemble those of other animals, each possessing a head, which is shaped
like an acorn, and a long vibratile tail by means of which it moves
through the water. In the cells of the spermary the spermatozoa are
closely packed together, with their heads pointing outwards towards the
summit of the mound through which they finally make their way into the
water. The aperture is formed by their own movements. Downing (Zool.
Jahrb. (Anat.) xxi, p. 379, 1905) and other authors have studied the
origin of the spermatozoa in great detail.

[Illustration: Fig. 28.--Eggs of _Hydra_ (magnified).

A=egg of _H. vulgaris_ (after Chun). B=vertical section through egg of
_H. oligactis_, form A (after Brauer). C=vertical section through egg of
_H. oligactis_, form B (after Brauer).]

The ovaries consist of rounded masses of cells lying at the base of the
ectoderm. One of these cells, the future egg, grows more rapidly than
the others, some or all of which it finally absorbs by means of lobose
pseudopodia extruded from its margin. It then makes its way by amoeboid
movements between the cells of the ectoderm until it reaches the
surface. In _H. vulgaris_ (Mem. Asiat. Soc. Beng. i, p. 350, 1906) the
egg is first visible with the aid of a lens as a minute star-shaped body
of an intense white colour lying at the base of the ectoderm cells. It
increases in size rapidly, gradually draws in its pseudopodia (the rays
of the star) and makes its way through the ectoderm to the exterior. The
process occupies not more than two hours. The issuing ovum does not
destroy the ectoderm cells as it passes out, but squeezes them together
round the aperture it makes. Owing to the pressure it exerts upon them,
they become much elongated and form a cup, in which the embryo rests on
the surface of the parent. By the time that the egg has become globular,
organic connection has ceased to exist. The embryo is held in position
partly by means of the cup of elongated ectoderm cells and partly by a
delicate film of mucus secreted by the parent. The most recent account
of the oogenesis ("ovogenesis") is by Downing (Zool. Jahrb. (Anat.)
xxvii, p. 295, 1909).


(b) _Budding._

The buds of _Hydra_ arise as hollow outgrowths from the wall of the
column, probably in a definite order and position in each species. The
tentacles are formed on the buds much as the buds themselves arise on
the column. There is much dispute as to the order in which these
structures appear on the bud, and Haacke (Jenaische Zeitschr. Naturwiss.
xiv, p. 133, 1880) has proposed to distinguish two species, _H.
trembleyi_ and _H. roeselii_, in accordance with the manner in which the
phenomenon is manifested. It seems probable, however, that the number of
tentacles that are developed in the first instance is due, at any rate
to some extent, to circumstances, for in the summer brood of _H.
vulgaris_ in Calcutta five usually appear simultaneously, while in the
winter brood of the same form four as a rule do so. Sometimes buds
remain attached to their parents sufficiently long to develop buds
themselves, so that temporary colonies of some complexity arise, but I
have not known this to occur in the case of Indian individuals.


(c) _Fission._

Reproduction by fission occurs naturally but not habitually in all
species of _Hydra_. It may take place either by a horizontal or by a
vertical division of the column. In the latter case it may be either
equal or unequal. If equal, it usually commences by an elongation in one
direction of the circumoral disk, which assumes a narrowly oval form;
the tentacles increase in number, and a notch appears at either side of
the disk and finally separates the column into two equal halves, each of
which is a complete polyp. The division sometimes commences at the base
of the column, but this is very rare. Transverse fission can be induced
artificially and is said to occur sometimes in natural conditions. It
commences by a constriction of the column which finally separates the
animal into two parts, the lower of which develops tentacles and a
mouth, while the upper part develops a basal disk. Unequal vertical
division occurs when the column is divided vertically in such a way that
the two resulting polyps are unequal in size. It is apparently not
accompanied by any great increase in the number of the tentacles, but
probably starts by one of the tentacles becoming forked and finally
splitting down the middle.

The question of the regeneration of lost parts in _Hydra_ cannot well be
separated from that of reproduction by fission. Over a hundred and fifty
years ago Trembley found that if a polyp were cut into several pieces,
each piece produced those structures necessary to render it a perfect
polyp. He also believed that he had induced a polyp that had been turned
inside out to adapt itself to circumstances and to reverse the functions
and structure of the two cellular layers of its body. In this, however,
he was probably mistaken, for there can be little doubt that his polyp
turned right side out while not under his immediate observation. Many
investigators have repeated some of his other experiments with success
in Europe, but the Calcutta _Hydra_ is too delicate an animal to survive
vivisection and invariably dies if lacerated. It appears that, even in
favourable circumstances, for a fresh polyp to be formed by artificial
fission it is necessary for the piece to contain cells of both
cell-layers.


DEVELOPMENT OF THE EGG.

The egg of _Hydra_ is said to be fertilized as it lies at the base of
the ectoderm, through which the fertilizing spermatozoon bores its way.
As soon as the egg has emerged from the cells of its parent it begins to
split up in such a manner as to form a hollow mass of comparatively
large equal cells. Smaller cells are separated off from these and soon
fill the central cavity. Before segmentation begins a delicate film of
mucus is secreted over the egg, and within this film the larger cells
secrete first a thick chitinous or horny egg-shell and within it a
delicate membrane. Development in some cases is delayed for a
considerable period, but sooner or later, by repeated division of the
cells, an oval hollow embryo is formed and escapes into the water by the
disintegration of the egg-shell and the subsequent rupture of the inner
membrane. Tentacles soon sprout out from one end of the embryo's body
and a mouth is formed; the column becomes more slender and attaches
itself by the aboral pole to some solid object.


ENEMIES.

_Hydra_ seems to have few natural enemies. Martin (Q. J. Micr. Sci.
London, lii, p. 261, 1908) has, however, described how the minute worm
_Microstoma lineare_ attacks _Hydra "rubra"_ in Scottish lochs, while
the larva of a midge devours _H. vulgaris_ in considerable numbers in
Calcutta tanks (p. 156).


COELENTERATES OF BRACKISH WATER.

Marine coelenterates of different orders not infrequently make their way
or are carried by the tide up the estuaries of rivers into brackish
water, and several species have been found living in isolated lagoons
and pools of which the water was distinctly salt or brackish. Among the
most remarkable instances of such isolation is the occurrence in Lake
Qurun in the Fayûm of Egypt of _Cordylophora lacustris_ and of the
peculiar little hydroid recently described by Mr. C. L. Boulenger as
_Moerisia lyonsi_ (Q. J. Micr. Sci. London, lii, p. 357, pls. xxii,
xxiii, 1908). In the delta of the Ganges there are numerous ponds which
have at one time been connected with estuaries or creeks of brackish
water and have become isolated either naturally or by the hand of man
without the marine element in their fauna by any means disappearing (p.
14). The following species have been found in such ponds:--

(_a_) _Hydrozoa._

(1) _Bimeria vestita_, Wright (1859).

Hincks, Hist. Brit. Hydr. Zooph. p. 103, pl. xv, fig. 2 (1868);
Annandale, Rec. Ind. Mus. i, p. 141, fig. 3 (1907).

This is a European species which has also been found off S. America. It
occurs not uncommonly in the creeks that penetrate into the Ganges delta
and has been found in pools of brackish water at Port Canning. The
Indian form is perhaps sufficiently distinct to be regarded as a
subspecies. The medusoid generation is suppressed in this genus.

(2) _Syncoryne filamentata_, Annandale (1907).

Annandale, Rec. Ind. Mus. i, p. 139, figs. 1, 2 (1907).

Both hydroid and medusæ were found in a small pool of brackish water at
Port Canning. The specific name refers to the fact that the ends of the
rhizomes from which the polyps arise are frequently free and elongate,
for the young polyp at the tip apparently takes some time to assume its
adult form.

(3) _Irene ceylonensis_, Browne (1905).

     Browne, in Herdman's Report on the Pearl Fisheries of
     Ceylon, iv, p. 140, pl. iii, figs. 9-11 (1905); Annandale,
     Rec. Ind. Mus. i, p. 142, fig. 4 (1907).

The medusa was originally taken off the coast of Ceylon, while the
hydroid was discovered in ponds of brackish water at Port Canning. It is
almost microscopic in size.

The first two of these species belong to the order Gymnoblastea
(Anthomedusæ) and the third to the Calyptoblastea (Leptomedusæ).

(b) _Actinozoa._

(4) _Sagartia schilleriana_, Stoliczka (1869).

     _S. schilleriana_, Stoliczka, Journ. As. Soc. Beng. (2)
     xxxviii, p. 28, pls. x, xi (1869); _Metridium
     schillerianum_, Annandale, Rec. Ind. Mus. i, p. 47, pl. iii
     (1907).

This sea-anemone, which has only been found in the delta of the Ganges,
offers a most remarkable instance of what appears to be rapid adaptation
of a species to its environment. The typical form, which was described
in 1869 by Stoliczka from specimens taken in tidal creeks and estuaries
in the Gangetic area and in the ponds at Port Canning, is found attached
to solid objects by its basal disk. The race (subsp. _exul_), however,
that is now found in the same ponds has become elongate in form and has
adopted a burrowing habit, apparently owing to the fact that the bottom
of the ponds in which it lives is soft and muddy.

In addition to these four species a minute hydroid belonging to the
order Gymnoblastea and now being described by Mr. J. Ritchie has been
taken in the ponds at Port Canning. It is a very aberrant form.


FRESHWATER COELENTERATES OTHER THAN HYDRA.

_Hydra_ is the only genus of coelenterates as yet found in fresh water
in India, but several others have been discovered in other countries.
They are:--

(1) _Cordylophora lacustris_, Allman (1843).

     Hincks, Hist. Brit. Hydr. Zooph. p. 16, pl. iii, fig. 2
     (1868).

This is a branching hydroid that does not produce free medusæ. It forms
bushy masses somewhat resembling those formed by a luxuriant growth of
_Plumatella fruticosa_ (pl. iii, fig. 1) in general appearance. _C.
lacustris_ is abundant in canals, rivers, and estuaries in many parts of
Europe and has recently been found in the isolated salt lake
Birket-el-Qurun in the Fayûm of Egypt.

(2) _Cordylophora whiteleggei_, v. Lendenfeld (1887).

     Zool. Jahrb. ii, p. 97 (1887).

A species or race of much feebler growth; as yet imperfectly known and
only recorded from fresh water in Australia.

_Cordylophora_ is a normal genus of the class Hydrozoa and the order
Gymnoblastea; the next four genera are certainly Hydrozoa, but their
affinities are very doubtful.

(3) _Microhydra ryderi_, Potts (1885).

     Potts, Q. J. Micr. Sci. London, l, p. 623, pls. xxxv, xxxvi;
     Browne, _ibid._ p. 635, pl. xxxvii (1906).

This animal, which has been found in N. America and in Germany,
possesses both an asexual hydroid and a sexual medusoid generation. The
former reproduces its species by direct budding as well as by giving
rise, also by a form of budding, to medusæ that become sexually mature.
The hydroid has no tentacles.

(4) _Limnocodium sowerbii_, Lankester (1880).

     Lankester, Q. J. Micr. Sci. London, xx, p. 351, pls. xxx,
     xxxi (1880); Fowler, _ibid._ xxx, p. 507, pl. xxxii (1890).

There is some doubt as to the different stages in the life-cycle of this
species. The medusa has been found in tanks in hot-houses in England,
France and Germany, and a minute hydroid closely resembling that of
_Microhydra ryderi_ has been associated with it provisionally.

(5) _Limnocodium kawaii_, Oka (1907).

     Oka, Annot. Zool. Japon. vi, p. 219, pl. viii (1907).

Only the medusa, which was taken in the R. Yang-tze-kiang, is as yet
known.

(6) _Limnocnida tanganyikæ_, Bohm (1889).

     R. T. Günther, Ann. Nat. Hist. (6) xi, p. 269, pls. xiii,
     xiv (1893).

Only the medusa, which is found in Lake Tanganyika, Lake Victoria Nyanza
and the R. Niger, has been found and it is doubtful whether a hydroid
generation exists.

(7) _Polypodium hydriforme_, Ussow (1885).

     Morph. Jahrb. xii, p. 137 (1887).

Two stages in this peculiar hydroid, which is found in the R. Volga, are
known, (_a_) a spiral ribbon-like form parasitic on the eggs of the
sterlet (_Acipenser ruthenus_), and (_b_) a small _Hydra_-like form with
both filamentous and club-shaped tentacles. The life-history has not yet
been worked out[AP].

     [Footnote AP: Since this was written, Lippen has described a
     third stage in the life-history of _Polypodium_ (Zool. Anz.
     Leipzig, xxxvii, Nr. 5, p. 97 (1911)).]


II.

HISTORY OF THE STUDY OF HYDRA.

Hydra was discovered by Leeuwenhoek at the beginning of the eighteenth
century and had attracted the attention of several skilful and accurate
observers before that century was half accomplished. Among them the
chief was Trembley, whose "Mémoires pour servir à l'histoire d'un genre
de Polype d'eau douce"* was published at Paris 1744, and is remarkable
not only for the extent and accuracy of the observations it enshrines
but also for the beauty of its plates. Baker in his work entitled "An
attempt towards a natural history of the Polyp"* (London, 1743) and
Rösel von Rosenhof in the third part of his "Insecten-Belustigung"
(Nurenberg, 1755) also made important contributions to the study of the
physiology and structure of _Hydra_ about the same period. Linné
invented the name _Hydra_, and in his "Fauna Sueica" and in the various
editions of his "Systema Naturæ" described several forms in a manner
that permits some of them to be recognized; but Linné did not
distinguish between the true _Hydra_ and other soft sessile
Coelenterates, and it is to Pallas ("Elenchus Zoophytorum," 1766) that
the credit properly belongs of reducing the genus to order. It is a
tribute to his insight that three of the four species he described are
still accepted as "good" by practically all students of the
Coelenterates, while the fourth was a form that he had not himself seen.

In the nineteenth century the freshwater polyp became a favourite object
of biological observation and was watched and examined by a host of
observers, among the more noteworthy of whom were Kleinenberg, Nussbaum,
and Brauer, who has since the beginning of the present century made an
important contribution to the taxonomy of the genus.


BIBLIOGRAPHY OF HYDRA.

_Hydra_ has been examined by thousands of students in biological
laboratories all over the civilized world, and the literature upon it is
hardly surpassed in magnitude by that on any other genus but _Homo_. The
following is a list of a few of the more important general memoirs and
of the papers that refer directly to Asiatic material. A systematic
bibliography is given by Bedot in his "Matériaux pour servir a
l'Histoire des Hydroïdes," Rev. Suisse Zool. xviii, fasc. 2 (1910).

(a) _General._

1743. BAKER, "An attempt towards a natural history of the Polyp"*
(London).

1744. TREMBLEY, "Mémoires pour servir à l'histoire d'un genre de polypes
d'eau douce"* (Paris).

1755. RÖSEL VON ROSENHOF, "Insecten-Belustigung: iii, Hist. Polyporum."

1766. PALLAS, "Elenchus Zoophytorum."

1844. LAURENT, "Rech. sur l'Hydre et l'Eponge d'eau douce" ("Voy. de la
Bonite, Zoophytologie").

1847. JOHNSTON, "A History of the British Zoophytes" (2nd edition).

1868. HINCKS, "History of British Hydroid Zoophytes."

1872. KLEINENBERG, "Hydra. Eine Anatomisch Entwicklungsgeschichtliche
Untersuchung."

1882. JICKELI, "Der Bau der Hydroidpolypen," Morph. Jahrb. viii, p. 373.

1887. NUSSBAUM, "Ueber die Theilbarkeit der lebendigen Materie. II.
Mittheilung. Beiträge zur Naturgeschichte des Genus Hydra," Arch. mikr.
Anat. Bonn, xxix, p. 265.

1891. BRAUER, "Über die Entwicklung von Hydra," Zeitschr. wiss. Zool.
Leipzig, lii, p. 169.

1892. CHUN, "Coelenterata (Hohlthiere)," in Bronn's Thier-Reichs II (2).

1905. DOWNING, "The spermatogenesis of Hydra," Zool. Jahrb. (Anat.) xxi,
p. 379.

1908. BRAUER, "Die Benennung und Unterscheidung der Hydra-Arten," Zool.
Ann. xxxiii, p. 790.

1909. FRISCHHOLZ, "Biologie und Systematik im Genus Hydra," Braun's
Annal. Zool. (Würzburg) iii, p. 105.

1910. BERNINGER, "Über Einwirkung des Hungers auf Hydra," Zool. Anz.
xxxvi, p. 271.

(b) _Asiatic References._

1894. RICHARD, "Sur quelques Animaux inférieurs des eaux douces du
Tonkin (Protozoaires, Rotifères, Entomostracés)," Mém. Soc. zool.
France, vii, p. 237.

1904. VON DADAY, "Mikroskopische Süsswasserthiere aus Turkestan," Zool.
Jahrb. (Syst.) xix, p. 469.

1906. ANNANDALE, "Notes on the Freshwater Fauna of India. No. IV. _Hydra
orientalis_ and its bionomical relations with other Invertebrates," J.
Asiat. Soc. Bengal (new series), ii, p. 109.

1906. ANNANDALE, "The Common _Hydra_ of Bengal: its Systematic Position
and Life History," Mem. As. Soc. Bengal, i, p. 339.

1907. ANNANDALE, "Notes on the Freshwater Fauna of India. No. X. _Hydra
orientalis_ during the Rains," J. Asiat. Soc. Bengal (new series), iii,
p. 27.

1907. ANNANDALE, "Notes on the Freshwater Fauna of India. No. XI.
Preliminary Note on the occurrence of a Medusa (_Irene ceylonensis_,
Browne) in a brackish pool in the Ganges Delta and on the Hydroid Stage
of the species," J. Asiat. Soc. Bengal (new series), iii, p. 79.

1907. WILLEY, "Freshwater Sponge and Hydra in Ceylon," Spolia Zeylan.
Colombo, iv, p. 184.

1908. ANNANDALE, "Observations on specimens of _Hydra_ from Tibet, with
notes on the distribution of the genus in Asia," Rec. Ind. Mus. ii, p.
311.

1910. POWELL, "Lessons in Practical Biology for Indian Students"
(Bombay).

1910. LLOYD, "An Introduction to Biology for Students in India"
(London).




GLOSSARY OF TECHNICAL TERMS USED IN PART II.


  _Aboral_ (or _basal_)       The disk by means of which a free polyp
  _disk_                      attaches itself to external objects.

  _Cnidoblast_                The living cell of the nematocyst or
                              nettle-cell (_q. v._).

  _Cnidocil_                  A minute bristle that projects on the
                              surface in connection with a nettle-cell
                              (_q. v._).

  _Column_                    The upright or potentially upright
                              part of a polyp (_q. v._).

  _Ectoderm_                  The external cell-layer of the body-wall.

  _Endoderm_                  The internal cell-layer of the body-wall.

  _Green (chlorophyll)        Minute green bodies contained in cells
   corpuscles_                of polyps or other animals and
                              representing a stage in the life-history
                              of an alga (_Chlorella_).

  _Mesogloea_                 The intermediate, gelatinous layer of
                              the body-wall.

  _Nettle-cell (nematocyst)_  A cell capsule full of liquid in which
                              an eversible thread is coiled up.

  _Oral disk_                 The eminence that surrounds the mouth
                              and is surrounded by tentacles.

  _Peristome_                 See "oral disk."

  _Polyp_                     An individual coelenterate of simple
                              structure that is fixed temporarily or
                              permanently by one end of a more
                              or less cylindrical body and possesses
                              a mouth at the other end.

  _Tentacles_                 Filamentous outgrowths (in _Hydra_
                              hollow) of the body-wall round the
                              mouth.




  LIST OF THE INDIAN HYDRIDA.


  Class HYDROZOA.

  Order ELEUTHEROBLASTEA.

  Family HYDRIDÆ.

  Genus HYDRA, _Linné_ (1746).

  24. _H. vulgaris_, Pallas (1766).

  25. _H. oligactis_, Pallas (1766).


Order ELEUTHEROBLASTEA.

Naked hydrozoa which reproduce their kind by means of buds or eggs, or
by fission, without exhibiting the phenomena of alternation of
generations.


Family HYDRIDÆ.

     HYDRAIDÆ, Johnston, Hist. Brit. Zooph. (ed. 2) i, p. 120
     (1847).
     HYDRIDÆ, Hincks, Hist. Brit. Hydroid. Zooph. p. 309 (1868).

Small Eleutheroblastea in which the mouth is surrounded by hollow
tentacles. Permanent colonies are not formed, but reproduction by
budding commonly takes place.


Genus HYDRA, _Linné_.

TYPE, _Hydra viridis_, Linné.

Freshwater polyps which produce eggs with hard chitinous shells.
Although habitually anchored by the end of the body furthest from the
mouth to extraneous objects, they possess considerable powers of
locomotion. They are extremely contractile and change greatly from time
to time in both form and size.

Only three well-established species of the genus, which is universally
distributed and occurs only in fresh or brackish[AQ] water, can be
recognized, namely, _H. viridis_, Linné (=_H. viridissima_, Pallas), _H.
vulgaris_, Pallas (=_H. grisea_, Linné), and _H. oligactis_, Pallas
(=_H. fusca_, Linné). The two latter occur in India, but _H. viridis_
does not appear to have been found as yet anywhere in the Oriental
Region, although it is common all over Europe and N. America and also in
Japan. The distribution of _H. vulgaris_ is probably cosmopolitan, but
there is some evidence that _H. oligactis_ avoids tropical districts,
although, under the name _Hydra fusca_, it has been doubtfully recorded
as occurring in Tonquin[AR].

     [Footnote AQ: A small form of _H. viridis_ (var. _bakeri_,
     Marshall) is found in brackish water in England.]

     [Footnote AR: Richard, Mém. Soc. zool. France, vii, p. 237
     (1894).]

The three species may be distinguished from one another by the following
key:--

  [I. Colour leaf-green; the cells contain green
       (chlorophyll) corpuscles of definite form.
     A. Tentacles comparatively stout, habitually
        shorter than the column, which is cylindrical.
        Egg-shell without spines, ornamented
        with a reticulate pattern                    _viridis_.]
  II. Colour never leaf-green; no chlorophyll
       corpuscles present in the cells.
     A. Tentacles capable of great elongation but
        when the animal is at rest never very much
        longer than the column, which is cylindrical
        when the gastral cavity is empty.
        Largest nettle-cells almost as broad as
        long. Egg-shell bearing long spines most
        of which are divided at the tips             _vulgaris_, p. 148.
     B. Tentacles, even when the animal is at rest,
        much longer than the column, the basal
        part of which, even when the gastral
        cavity is empty, is constricted. Largest
        nettle-cells considerably longer than
        broad.  Egg-shell smooth or bearing
        short, simple spines                         _oligactis_, p. 158.


24. Hydra vulgaris, _Pallas_.

     Polypes de la seconde espèce, Trembley, Mém. pour servir à
     l'histoire d'un genre de polypes d'eau douce*, pl. i, figs.
     2, 5; pl. vi, figs. 2, 8; pl. viii, figs. 1-7; pl. xi, figs.
     11-13 (1744).

     Rösel von Rosenhof, Insecten-Belustigung, iii, Hist.
     Polyporum, pls. lxxvi, lxxvii, lxxix-lxxxiii (1755).

     ? _Hydra polypus_, Linné, Fauna Suecica, p. 542 (1761).

     _Hydra vulgaris_, Pallas, Elenchus Zoophytorum, p. 30
     (1766).

     ? _Hydra attenuata_, _id_., _ibid_. p. 32.

     _Hydra grisea_, Linné (Gmelin), Systema Naturæ (ed. 13), p.
     3870 (1782).

     _Hydra pallens_, _id_., _ibid_. p. 3871.

     _Hydra vulgaris_, Ehrenberg, Abhandl. Akad. Wiss. Berlin,
     1836, p. 134, taf. ii.

     _Hydra brunnea_, Templeton, London's Mag. Nat. Hist. ix, p.
     417 (1836).

     _Hydra vulgaris_, Laurent, Rech. sur l'Hydre at l'Éponge
     d'eau douce (Voy. de la Bonite, Zoophytologie), p. 11, pl.
     i, pl. ii, figs. 2, 2'' (1844).

     _Hydra vulgaris_, Johnston, Hist. British Zoophytes (ed. 2),
     i, p. 122, pl. xxix, fig. 2 (1847).

     _Hydra vulgaris_, Hincks, Hist. British Hydroid Zoophytes,
     i, p. 314, fig. 41 (1868).

     _Hydra aurantiaca_, Kleinenberg, Hydra, p. 70, pl. i, fig.
     1, pl. iii, fig. 10 (1872).

     _Hydra trembleyi_, Haacke, Zool. Anz. Leipzig, ii, p. 622
     (1879).

     _Hydra grisea_, Jickeli, Morph. Jahrb. viii, p. 391, pl.
     xviii, fig. 2 (1883).

     _Hydra grisea_, Nussbaum, Arch. mikr. Anat. Bonn, xxix, p.
     272, pl. xiii, pl. xiv, figs. 33, 37, 47 (1887).

     ? _Hydra hexactinella_, v. Lendenfeld, Zool. Jahrb. Jena,
     ii, p. 96, pl. vi, figs. 13, 14 (1887).

     ? _Hydra hexactinella_, _id_., Proc. Linn. Soc. N. S. Wales,
     x, p. 678, p. xlviii, figs. 1-4 (1887).

     _Hydra grisea_, Brauer, Zeit. wiss. Zool. Leipzig, lii, p.
     169 (1891).

     _Hydra grisea_, Chun, in Brönn's Thier-Reichs, ii (2), pl.
     ii, figs. 2_b_, 2_c_, 5 (1892).

     _Hydra grisea_, Downing, Zool. Jahrb. (Anat.) Jena, xxi, p.
     381 (1905).

     _Hydra orientalis_, Annandale, J. Asiat. Soc. Bengal, (new
     series) i, 1905, p. 72.

     _Hydra orientalis_, _id._, _ibid._ (new series) ii, 1906, p.
     109.

     _Hydra orientalis_, _id._, Mem. Asiat. Soc. Bengal, i, p.
     340 (1906).

     ? _Hydra orientalis_, Willey, Spol. Zeylan. Colombo, iv, p.
     185 (1907).

     _Hydra grisea_, Weltner, Arch. Naturg. Berlin, lxxiii, i, p.
     475 (1907).

     _Hydra vulgaris_, Brauer, Zool. Anz. xxxiii, p. 792, fig. 1
     (1908).

     _Hydra orientalis_, Annandale, Rec. Ind. Mus. ii, p. 312
     (1908).

     _Hydra grisea_, Frischholz, Braun's Zool. Annal. (Würzburg),
     iii, pp. 107, 134, &c., figs. 1 and 10-17 (1909).

     _Hydra grisea_, _id._, Biol. Centralbl. Berlin, xxix, p. 184
     (1909).

     _Hydra vulgaris_, Brauer, Die Süsswasserfauna Deutschlands,
     xix, p. 192, figs. 336-338 (1909).

     _Hydra pentactinella_, Powell, Lessons in Practical Biology
     for Indian Students, p. 24 (Bombay, 1910).


Phase _orientalis*_, Annandale.

_Colour_ variable; in summer usually pale, in winter either deep orange,
dull brown, or dark green. The cells do not contain spherical or oval
coloured bodies.

[Illustration: Fig. 29.--_Hydra vulgaris_, from Calcutta (phase
_orientalis_).

A=winter brood; B=summer brood, the same individual in an expanded and a
contracted condition. B is more highly magnified than A.]

_Column_ slender and capable of great elongation, normally almost
cylindrical, but when containing food often shaped like a wine-glass.
The surface is thickly set with nettle-cells the cnidocils of which give
it an almost hirsute appearance under the microscope. When extended to
the utmost the column is sometimes nearly 30 mm. (1-1/5 inches) long,
but more commonly it is about half that length or even shorter.

_Tentacles_ usually 4-6, occasionally 8. They are always slender except
when they are contracted, then becoming swollen at the base and slightly
globular at the tip. If the animal is at rest they are not very much
longer than the body, but if it is hungry or about to move from one
place to another they are capable of very great extension, often
becoming like a string of minute beads (the groups of nettle-cells)
strung on an invisible wire.

_Nettle-cells._ The capsules with barbed threads (fig. 27, p. 131) are
very variable in size, but they are invariably broad in proportion to
their length and as a rule nearly spherical. In a _Hydra_ taken in
Calcutta during the winter the largest capsules measured (unexploded)
0.0189 mm. in breadth and 0.019 in length, but in summer they are
smaller (about 0.012 mm. in breadth). Smaller capsules with barbed
threads always occur. The barbed threads are very long and slender. At
their base they bear a circle of stout and prominent spines, usually 4
in number; above these there are a number of very small spines, but the
small spines are usually obscure. Malformed corpuscles are common. The
capsules with unbarbed threads are very nearly as broad at the distal as
at the proximal end; they are broadly oval with rounded ends.

_Reproductive organs._ The reproductive organs are confined to the upper
part of the body. In India eggs (fig. 28, p. 137) are seldom produced.
They sometimes appear, however, at the beginning of the hot weather. In
form they are spherical, and their shell bears relatively long spines,
which are expanded, flattened and more or less divided at the tip. The
part of the egg that is in contact with the parent-polyp is bare.
Spermaries are produced more readily than ovaries; they are mammillate
in form and number from 4 to 24. Ovaries and spermaries have not been
found on the same individual.

_Buds_ are confined to a narrow zone nearer the base than the apex of
the column. Rarely more than 2 are produced at a time, and I have never
seen an attached bud budding. In winter 5 tentacles are as a rule
produced simultaneously, and in summer 4. In the former case a fifth
often makes its appearance before the bud is liberated.

In Calcutta two broods can be distinguished, a cold-weather brood, which
is larger, stouter, and more deeply coloured, produces buds more freely,
has larger nematocysts, and as a rule possesses 6 tentacles; and a
hot-weather brood, which is smaller, more slender and paler, produces
buds very sparingly, has smaller nematocysts, and as a rule possesses
only 4 or 5 tentacles. Only the cold-weather form is known to become
sexually mature. There is evidence, however, that in those parts of
India which enjoy a more uniform tropical climate than Lower Bengal,
polyps found at all times of year resemble those found in the hot
weather in Calcutta, and sometimes produce spermatozoa or eggs.

I have recently had an opportunity of comparing specimens of the
Calcutta hot-weather form with well-preserved examples of _H. vulgaris_,
Pallas (=_H. grisea_, Linn.), from England. They differ from these
polyps in very much the same way as, but to a greater degree than they
do from the winter phase of their own race, and I have therefore no
doubt that _H. orientalis_ is merely a tropical phase of Pallas's
species. My description is based on Indian specimens, which seem to
differ, so far as anatomy is concerned, from European ones in the
following points:--

     (1) The sexes are invariably distinct;
     (2) the nematocysts are invariably smaller.

I have seen in Burma an abnormal individual with no tentacles. Its buds,
however, possessed these organs.

TYPE. None of the older types of _Hydra_ are now in existence. That of
_H. orientalis_ is, however, in the collection of the Indian Museum.

GEOGRAPHICAL DISTRIBUTION.--_H. vulgaris_ is common in Europe and N.
America and is probably found all over tropical Asia. The following are
Indian and Ceylon localities:--BENGAL, Calcutta and neighbourhood
(_Annandale_, _Lloyd_); Adra, Manbhum district (_Paiva_), Rampur Bhulia
on the R. Ganges (_Annandale_); Chakradharpur, Chota Nagpur
(_Annandale_); Pusa, Bihar (_Annandale_); Puri, Orissa (_Annandale_):
MADRAS, sea-beach near Madras town (_Henderson_): BOMBAY, island of
Bombay (_Powell_): BURMA, Mandalay, Upper Burma, and Moulmein, N.
Tenasserim (_Annandale_): CEYLON, Colombo and Peradeniya (_Willey_,
_Green_). Dr. A. D. Imms tells me that he has obtained specimens that
probably belong to this species in the Jumna at Allahabad.

BIOLOGY.--In India _H. vulgaris_ is usually found, so far as my
experience goes, in stagnant water. In Calcutta it is most abundant in
ponds containing plenty of aquatic vegetation, and seems to be
especially partial to the plant _Limnanthemum_, which has floating
leaves attached to thin stalks that spring up from the bottom, and to
_Lemna_ (duckweed). Dr. Henderson, however, found specimens in a pool of
rain-water on the sea-shore near Madras.

There is evidence that each of the two broods which occur in Lower
Bengal represents at least one generation; probably it represents more
than one, for tentacles are rarely if ever produced after the animal has
obtained its full size, and never (or only owing to accident) decrease
in number after they have once appeared. The winter form is found
chiefly near the surface of the water, especially on the roots of
duckweed and on the lower surface of the leaves of _Limnanthemum_; but
the summer form affects deeper water in shady places, and as a rule
attaches itself to wholly submerged plants. The latter form is to be met
with between March and October, the cold-weather form between October
and March, both being sometimes found together at the periods of
transition. In the unnatural environment of an aquarium, however,
individuals of the winter form lose their colour and become attenuated,
in these features resembling the summer form, even in the cooler months.
Buds produced in these conditions rarely have more than five tentacles
or themselves produce buds freely after liberation.

The buds appear in a fixed order and position, at any rate on
individuals examined in winter; in specimens of the summer form the
position is fixed, but the order is irregular. Each quadrant of the
column has apparently the power of producing, in a definite zone nearer
the aboral pole than the mouth, a single bud; but the buds of the
different quadrants are not produced simultaneously. If we imagine that
the quadrants face north, south, east, and west, and that the first bud
is produced in the north quadrant, the second will be produced in the
east quadrant, the third in the south, and the fourth in the west. It is
doubtful whether more than four buds are produced in the lifetime of an
individual, and apparently attached buds never bud in this race. The
second bud usually appears before the first is liberated, and this is
also the case occasionally as regards the third, but it is exceptional
for four buds to be present at one time. About three weeks usually
elapse between the date at which the bud first appears as a minute
conical projection on the surface of the parent and that at which it
liberates itself. This it does by bending down, fixing itself to some
solid object by means of the tips of its tentacles, the gland-cells of
which secrete a gummy fluid, and then tearing itself free.

Although it is rare for more than two buds to be produced
simultaneously, budding is apparently a more usual form of reproduction
than sexual reproduction. Individuals that bear eggs have not yet been
found in India in natural conditions, although males with functional
spermaries are not uncommon at the approach of the hot weather. The few
eggs that I have seen were produced in my aquarium towards the end of
the cold weather. Starvation, lack of oxygen, and too high a temperature
(perhaps also lack of light) appear to stimulate the growth of the male
organs in ordinary cases, but perhaps they induce the development of
ovaries in the case of individuals that are unusually well nourished.

The spines that cover the egg retain débris of various kinds upon its
surface, so that it becomes more or less completely concealed by a
covering of fragments of dead leaves and the like even before it is
separated from the polyp. Its separation is brought about by its falling
off the column of the parent. Nothing is known of its subsequent fate,
but probably it lies dormant in the mud through the hot weather. Eggs
are sometimes produced that have no shells. This is probably due to the
fact that they have not been fertilized.

Reproduction by fission occurs rarely in the Indian _Hydra_, but both
equal and unequal vertical fission have been observed. In the case of
equal fission the circumoral area lengthens in a horizontal direction,
and as many extra tentacles as those the polyp already possesses make
their appearance. The mouth then becomes constricted in the middle and
notches corresponding to its constriction appear at either side of the
upper part of the column. Finally the whole animal divides into two
equal halves in a vertical direction. I have only seen one instance of
what appeared to be unequal vertical fission--that of a polyp consisting
of two individuals still joined together by the basal disk, but one
about half the size of the other. Each had three well-developed
tentacles, and in addition a minute fourth tentacle. This was situated
on the side opposed to that of the other individual which bore a similar
tentacle. Transverse fission has not been observed. The Indian _Hydra_
is a very delicate animal as compared with such a form as _H. viridis_,
and all attempts to produce artificial fission without killing the polyp
have as yet failed.

Young individuals are often, and adults occasionally, found floating
free in the water, either with the mouth uppermost and the tentacles
extended so as to cover as large an area as possible or with the aboral
pole at the surface. In the former case they float in mid-water, being
of nearly the same specific gravity as the water, and are carried about
by any movement set up in it. In the latter case, however, the base of
the column is actually attached to some small object such as the cast
skin of a water-flea or to a minute drop of mucus originally given out
by the polyp's own mouth; the tentacles either hang downwards or are
spread out round the mouth, and the animal is carried about by wind or
other agencies acting on the surface.

In addition to this passive method of progression the polyp can crawl
with considerable rapidity. In doing so it bends its column down to the
object along which it is about to move in such a way that it lies almost
parallel to the surface, the basal disk, however, being still attached.
The tentacles are then extended and attach themselves near the tips to
the surface a considerable distance away. Attachment is effected by the
secretion of minute drops of adhesive substance from gland-cells. The
basal disk is liberated and the tentacles contract, dragging the column,
which still lies prone, along as they do so. The basal disk again
affixes itself, the tentacles wrench themselves free, the surface of
their cells being often drawn out in the process into pseudopodia-like
projections, which of course are not true pseudopodia[AS] but merely
projections produced by the mechanical strain. The whole action is then
repeated. The polyp can also pull itself across a space such as that
between two stems or leaves by stretching out one of its tentacles,
fixing the tip to the object it desires to reach, pulling itself free
from its former point of attachment, and dragging itself across by
contracting the fixed tentacle. The basal disk is then turned round and
fixed to the new support.

     [Footnote AS: See Zykoff, Biol. Centralbl. xviii, p. 272
     (1898), and Annandale, Rec. Ind. Mus. i, p. 67 (1907).]

The Indian polyp, like all its congeners, is attracted by light, but it
is more strongly repelled by heat. Probably it never moves in a straight
line, but if direct sunlight falls on one side of a glass aquarium, the
polyps move away from that side in a much less erratic course than is
usually the case. If conditions are favourable, they often remain in one
spot for weeks at a time, their buds congregating round them as they are
set free. In a natural environment it seems that regular migrations take
place in accordance with changes in temperature, for whereas in cool
weather many individuals are found adhering to the lower surface of the
floating leaves of _Limnanthemum_, few are found in this position
immediately after a rise in the thermometer. If the rise is only a small
one, they merely crawl down the stems to the end of which the leaves are
attached, but as soon as the hot weather begins in earnest, the few that
survive make their way to the deepest and most shady part of the pond.
In captivity the polyps seek the bottom of any vessel in which they are
contained, if sunlight falls on the surface of the water.

The chief function of the tentacles is that of capturing prey. The
Indian polyp feeds as a rule in the early morning, before the day has
become hot. In an aquarium at any rate, the tentacles are never more
than moderately extended during the night. If the polyp is hungry, they
are extended to their greatest length in the early morning, and if prey
is not captured, they sometimes remain in this condition throughout the
day. In these circumstances they hang down or stand up in the water
closely parallel to one another, and often curved in the middle as if a
current were directed against them. Prey that comes in contact with one
of them has little chance of escape, for nematocysts from all the
tentacles can be readily discharged against it. Approximately once in
half an hour the direction of the tentacles is changed, but I have been
unable to observe any regular rhythmical movements of the tentacles or
any correlation between those of a parent polyp and the buds still
attached to it.

The prey consists chiefly of the young larvæ of midges (Chironomidæ) and
may-flies, but small copepod and phyllopod crustacea are also captured.

As soon as the prey adheres firmly to the tentacles and has become
paralysed it is brought to the mouth by their contracting strongly and
is involved in a mass of colourless mucus extruded from the digestive
cavity. Partly by the contraction of muscle-fibres in the body-wall and
partly by movements of the mouth itself assisted by the mucus, which
apparently remains attached to the walls of the cavity, the food is
brought into the mouth. If it is at all bulky, it remains in the upper
part of the cavity, the gland-cells pouring out a digestive fluid upon
it and so dissolving out soluble substances. A large share of the
substances thus prepared falls down to the bottom of the cavity and are
there digested by the endoderm cells. The insoluble parts of the food
are, however, ejected from the mouth without ever reaching the base of
the cavity.

The colour of the polyp appears to be due mainly to the results of
digestion. Brown or orange individuals recently captured in a pond and
kept in favourable conditions take three or four days to digest their
food, and the excreta ejected from the mouth then take the form of a
white flocculent mass. If, however, the same individuals are kept for
long in a glass aquarium, they lose their colour, even though they feed
readily. Digestion is then a much more rapid process, and the excreta
contain minute, irregular, coloured granules, which appear to be
identical with those contained in the endoderm cells of individuals that
have recently digested a meal fully. Starved individuals are always
nearly colourless. It seems, therefore, that in this species colour is
due directly to the products of digestion, and that digestion does not
take place so fully in unfavourable conditions or at a high temperature
as it does in more healthy circumstances. The dark green colour of some
polyps is, however, less easily explained. I have noticed that all the
individuals which have produced eggs in my aquarium have been of this
colour, which they have retained in spite of captivity; whereas
individuals that produced spermatozoa often lost their colour completely
before doing so, sometimes becoming of a milky white owing to the
accumulation of minute drops of liquid in their endoderm cells. Even in
green individuals there is never any trace in the cells of coloured
bodies of a definite form.

The Indian polyp, unlike European representatives of its species, is a
very delicate little animal. In captivity at any rate, three
circumstances are most inimical to its life: firstly, a sudden rise in
the temperature, which may either kill the polyp directly or cause it to
hasten its decease by becoming sexually mature; secondly, the lack of a
free current of air on the surface of the aquarium; and thirdly, the
growth of a bacterium, which forms a scum on the top of the water and
clogs up the interstices between the leaves and stems of the
water-plants, soon killing them. If adult polyps are kept even in a
shallow opaque vessel which is shut up in a room with closed shutters
they generally die in a single night; indeed, they rarely survive for
more than a few days unless the vessel is placed in such a position that
air is moving almost continuously over its surface. The bacterium to
which I allude often almost seals up the aquarium, especially in March
and April, in which months its growth is very rapid. Strands of slime
produced by it surround the polyp and even enter its mouth. In this
event the polyp retracts its tentacles until they become mere
prominences on its disk, and shrinks greatly in size. The colouring
matter in its body becomes broken up into irregular patches owing to
degeneracy of the endoderm cells, and it dies within a few hours.

_Hydra_ in Calcutta is often devoured by the larva of a small midge
(_Chironomus fasciatipennis_, Kieffer) common in the tanks from November
to February. In the early stages of its larval life this insect wanders
free among communities of protozoa (_Vorticella_, _Epistylis_, &c.) and
rotifers on which it feeds, but as maturity approaches begins to build
for itself a temporary shelter of one of two kinds, either a delicate
silken tunnel the base of which is formed by some smooth natural
surface, or a regular tube the base of which is fixed by a stalk
situated near the middle of its length to some solid object, while the
whole surface is covered with little projections. The nature of the
covering appears to depend partly on that of the food-supply and partly
on whether the larva is about to change its skin.

I had frequently noticed that tunnels brought from the tank on the under
surface of _Limnanthemum_ leaves had a _Hydra_ fixed to them. This
occurred in about a third of the occupied shelters examined. The _Hydra_
was always in a contracted condition and often more or less mutilated.
By keeping a larva together with a free polyp in a glass of clean water,
I have been able to observe the manner in which the polyp is captured
and entangled. The larva settles down near the base of its column and
commences to spin a tunnel. When this is partially completed, it passes
a thread round the polyp's body to which it gives a sharp bite. This
causes the polyp to bend down its tentacles, which the larva entangles
with threads of silk, doing so by means of rapid, darting movements; for
the nettle-cells would prove fatal should they be shot out against its
body, which is soft. Its head is probably too thickly coated with chitin
to excite their discharge. Indeed, small larvæ of this very species form
no inconsiderable part of the food of the polyp, and, so far as my
observations go, a larva is always attacked in the body and swallowed in
a doubled-up position.

When the _Hydra_ has been firmly built into the wall of the shelters and
its tentacles fastened down by their bases on the roof, the larva
proceeds, sometimes after an interval of some hours, to eat the body,
which it does very rapidly, leaving the tentacles attached to its
shelter. The meal only lasts for a few minutes; after it the larva
enjoys several hours' repose, protected by remains of its victim, which
retain a kind of vitality for some time. During this period it remains
still, except for certain undulatory movements of the posterior part of
the body which probably aid in respiration. Then it leaves the shelter
and goes in search of further prey. Its food, even when living in a
tunnel, does not consist entirely of _Hydra_. I have watched a larva
building its shelter near a number of rotifers, some of which it
devoured and some of which it plastered on to its tunnel.

The tubular shelters occasionally found are very much stouter structures
than the tunnels, but are apparently made fundamentally of the same
materials; and structures intermediate between them and the tunnels are
sometimes produced. The larva as a rule fastens to them branches
detached from living colonies of Vorticellid protozoa such as
_Epistylis_[AT].

     [Footnote AT: Further particulars regarding the life-history
     of this larva will be found on pp. 114 and 115, J. Asiat.
     Soc. Bengal, ii (n. s.) 1906.]

Of animals living in more or less intimate relations with the polyp, I
have found two very distinct species of protozoa, neither of which is
identical with either of the two commonly found in association with
_Hydra_ in Europe, _Trichodina pediculus_ and _Kerona polyporum_. On two
occasions, one in January and the other at the beginning of February, I
have seen a minute colourless flagellate on the tentacles of the
Calcutta polyp. On the first occasion the tentacles were completely
covered with this protozoon, so that they appeared at first sight as
though encased in flagellated epithelium. The minute organism was
colourless, transparent, considerably larger than the spermatozoa of
_Hydra_, slightly constricted in the middle and rounded at each end. It
bore a long flagellum at the end furthest from its point of attachment,
the method of which I could not ascertain. When separated from the polyp
little groups clung together in rosettes and gyrated in the water. On
the other occasion only a few individuals were observed. Possibly this
flagellate was a parasite rather than a commensal, as the individual on
which it swarmed was unusually emaciated and colourless, and bore
neither gonads nor buds. The larger stinging cells were completely
covered by groups of the organism, and possibly this may have interfered
with the discharge of stinging threads.

The other protozoon was _Vorticella monilata_, Tatem, which has been
found, not in association with _Hydra_, in Europe and S. America. In
Calcutta I have only seen it attached to the column of the polyp, but
probably it would also be found, if carefully looked for, attached to
water-weeds.

Especially in the four-rayed stage, the polyp not infrequently attaches
itself to shells of _Vivipara_, and, more rarely, to those of other
molluscs. It is doubtful whether this temporary association between
_Hydra_ and the mollusc is of any importance to the latter. Even when
the polyp settles on its body and not on its shell (as is sometimes the
case) the _Vivipara_ appears to suffer no inconvenience, and makes no
attempt to get rid of its burden. It is possible, on the other hand,
that the _Hydra_ may protect it by devouring would-be parasites; but of
this there is no evidence[AU].

     [Footnote AU: In the Calcutta tanks operculate molluscs such
     as _Vivipara_ are certainly more free from visible attack
     than non-operculate species. This is the case for instance,
     as regards the common aquatic glowworm (_Luciola_ sp.),
     which destroys large numbers of individuals of _Limnophysa_,
     _Limnæus_, &c. If it has been starved for several days in an
     aquarium it will attack an operculate form, but rarely with
     success. Similarly _Chætogaster bengalensis_ attaches itself
     exclusively to non-operculate forms. In the one case the
     polyp could do very little against an adversary with so
     stout an integument as the insect, while, in the other, it
     is doubtful whether the worm does any harm to its host. The
     polyp would afford very little protection against the
     snail's vertebrate enemies or against what appears to be its
     chief foe, namely, drought. As the water sinks in the tank
     non-operculate species migrate to the deeper parts, but
     _Vivipara_ and _Ampullaria_ close their shells, remain where
     they are, and so often perish, being left high and dry,
     exposed to the heat of the sun.]

The association, however, is undoubtedly useful to _Hydra_. The mud on
the shells of _Vivipara_ taken on floating objects shows that in cool
weather the snail comes up from the bottom to the surface, and it
probably goes in the opposite direction in hot weather. Moreover, the
common Calcutta species (_V. bengalensis_) feeds very largely, if not
exclusively, on minute green algæ. It therefore naturally moves towards
spots where smaller forms of animal and vegetable life abound and
conditions are favourable for the polyp. The polyp's means of
progression are limited, and the use of a beast of burden is most
advantageous to it, for it can detach itself when it arrives at a
favourable habitat. If specimens are kept in water which is allowed to
become foul, a very large proportion of them will attach themselves to
any snails confined with them. Under natural conditions they would thus
in all probability be rapidly conveyed to a more suitable environment.
In the tanks it is far commoner to find young four-rayed polyps on
_Vivipara_ than individuals with five or six rays; but the adults of the
species are far less prone to change their position than are the young.

The Calcutta _Hydra_, especially in spring, exhibits a distinct tendency
to frequent the neighbourhood of sponges and polyzoa, such as _Spongilla
carteri_ and the denser forms of _Plumatella_. Possibly this is owing to
the shade these organisms provide.


25. Hydra oligactis, _Pallas_.

     Polypes de la troisième espèce, Trembley, Mém. hist.
     Polypes,* pl. i, figs. 3, 4, 6; pl. ii, figs. 1-4; pl. iii,
     fig. 11; pl. v, figs. 1-4; pl. vi, figs. 3-7, 9, 10; pl.
     viii, figs. 8, 11; pl. ix (1744).

     Rösel von Rosenhof, Insekt.-Belustigung, iii, Hist. Polyp.,
     pls. lxxxiv-lxxxvi (1755).

     _Hydra socialis_, Linné, Fauna Sueica, p. 542 (1761).

     _Hydra oligactis_, Pallas, Elench. Zooph. p. 29 (1766).

     ? _Hydra attenuata_, _id._, _ibid._ p. 32.

     _Hydra fusca_, Linné, Syst. Nat. (ed. 13), p. 3870 (1782).

     _Hydra oligactis_, Johnston, Brit. Zooph. i, p. 124, fig. 27
     (p. 120) (1847).

     _Hydra oligactis_, Hincks, Hist. Brit. Hydr. Zooph. i, p.
     315, fig. 42 (1868).

     _Hydra roeselii_, Haacke, Jena Zeitschr. Naturwiss. xiv, p.
     135 (1880).

     ? _Hydra rhætica_, Asper, Zool. Anz. 1880, p. 204, figs.
     1-3.

     _Hydra vulgaris_, Jickeli (_nec_ Pallas), Morph. Jahrb.
     viii, p. 391, pl. xviii, fig. 3 (1882).

     _Hydra fusca_, Nussbaum, Arch. mikr. Anat. Bonn, xxix, p.
     273, pl. xiv, figs. 34-36, pl. xv, figs. 48-51, &c. (1887).

     _Hydra fusca_, Brauer, Zeit. wiss. Zool. Leipzig, lii, p.
     177, pl. xi, figs. 2, 5, 6; pl. xii, fig. 6 (1891).

     _Hydra_ sp. ? _id._, _ibid._ pl. xi, figs. 3, 3a, 4, 7, 8;
     pl. xii, figs. 1, 2, 5-13.

     _Hydra fusca_, Chun in Brönn's Thier-Reichs, ii (2), pl. ii,
     figs. 2(_a_), 4, 6 (1892).

     _Hydra monoecia_, Downing, Science* (5) xii, p. 228.

     _Hydra fusca_, _id._, Zool. Jahrb. (Anat.) xxi, p. 382
     (1905).

     _Hydra dioecia_, _id._, _ibid._ pl. xxiii, figs. 6, 7, &c.

     _Hydra fusca_, Hertwig, Biol. Centralbl. xxvi, p. 489
     (1906).

     _Hydra oligactis_, Brauer, Zool. Anz. xxxiii, p. 792, fig. 2
     (1908).

     _Hydra polypus_, _id._, _ibid._

     _Hydra fusca_, Frischholz, Ann. Zool. (Würzburg), iii, p.
     114, figs. 2-9 (1909).

     _Hydra oligactis_, Brauer, Süsswasserfauna Deutschl. xix, p.
          193, figs. 339-341 (1909).

     _Hydra polypus_, _id._, _ibid._ figs. 342-344.

This species differs from _H. vulgaris_ in the following characters:--

     (1) Even when the gastral cavity is empty, the basal part of
     the column is distinctly more slender than the upper part;
     (2) even when the animal is at rest, the tentacles are much
     longer than the column;
     (3) the nettle-cells of both types are usually smaller and
     more uniform in size than in the other species; those with
     barbed threads (fig. 27, p. 131) are always flask-shaped and
     somewhat narrower in proportion to their length, while those
     with simple threads are pointed or almost pointed at their
     distal end;
     (4) the stinging threads of the more complex form are
     comparatively stout and short;
     (5) there are comparatively few nettle-cells in the column;
     (6) the egg-shell is nearly smooth or covered more or less
     completely with short, simple spines (fig. 28, p. 137).

_H. oligactis_ is usually a more vigorous form than _H. vulgaris_ and,
in spite of its name, has often a considerable number of tentacles. The
few Indian specimens examined have, however, been small and have not had
more than six tentacles. I have not seen an Indian specimen with more
than two buds, but European specimens sometimes produce a great many,
and as the daughter buds do not always separate from the parent until
they have themselves produced buds, temporary colonies of some
complexity arise; Chun figures a specimen with nineteen daughter and
granddaughter buds[AV].

     [Footnote AV: Pallas writes as regards this "pulcherrime
     vegetantem varietatem" with his usual critical insight, "Vix
     tamen peculiaris speciei nomine salutanda videtur." It is
     probably the _Hydra socialis_ of Linné.]

In Europe and N. America there appear to be two races or phases of the
species. To avoid ambiguity they may be called form A and form B and
described as follows:--

   Form A is of vigorous growth. It is as a rule dioecious, and
     its reproductive organs may be borne practically at any
     level on the surface of the column. Its eggs are spherical
     and as a rule covered almost uniformly with spines.

   Form B is smaller and has smaller and more variable
     nettle-cells. Its reproductive organs are borne only on the
     distal third or at the base of its column and it is often
     monoecious. The lower surface of its egg is flattened,
     adherent, and devoid of spines.

The larger form (A) was originally named _Hydra monoecia_ by Downing,
who in 1904 expressed a wish to substitute for the specific name, which
had been given through inadvertence, the more appropriate one _dioecia_.
As, however, it appears to be the commoner of the two in northern
Europe, we may regard it as probably being the one named _Hydra
oligactis_ by Pallas and therefore may accept it as the _forma typica_
of that species. According to Brauer (1908) the smaller form is Linné's
_Hydra polypus_; but the original description of the "species" hardly
bears out this view. As reproductive organs have not yet been found in
Indian specimens, it is impossible to say to which of the two forms they
belong.

A red form of _H. oligactis_ occurs in Tibet in the lake Rham-tso, at an
altitude of about 15,000 feet and has been reported from various small
lakes in mountainous parts of Europe. It is probably the form called
_Hydra rhætica_ by Asper, but his figures are lacking in detail and
appear to have been drawn from specimens in a state of partial
contraction. _H. rubra_, Lewes (Ann. Mag. Nat. Hist. (3) v, p. 71,
1860), may also be identical with this form. Roux, indeed, states that
_H. rubra_ is only found living unattached at considerable depths (Ann.
Biol. lacustre ii, p. 266, 1907); but this statement does not accord
with the fact that Lewes's specimens were found in ponds on Wimbledon
Common.

TYPE not in existence.

GEOGRAPHICAL DISTRIBUTION.--_H. oligactis_ is widely distributed in
Europe and N. America, but in India has only been found in and near the
city of Lahore in the Punjab.

BIOLOGY.--This species was found by Major J. Stephenson, I.M.S., in the
basin of a fountain at Lahore and in an ornamental canal in the Shalimar
Gardens on the outskirts of the same city. Nothing is known as regards
its habits in this country. In N. America, according to Downing, form B
breeds in September and October and form A from October to December. The
eggs of form B remain attached to the parent until the two cellular
layers are formed and then drop off, whereas those of form A are fixed
by the parent to some extraneous object, its column contracting until
they are in a favourable position for attachment.

The colour of Indian examples of _H. oligactis_ apparently resembles
that of the Calcutta winter brood of _H. vulgaris_ so far as visual
effect is concerned, but I have noticed in specimens from Lahore and the
neighbourhood that very minute spherical bodies of a dark green colour
are present in the endoderm cells.




  PART III.

  FRESHWATER POLYZOA

  (CTENOSTOMATA & PHYLACTOLÆMATA).




INTRODUCTION TO PART III.


I.

STATUS AND STRUCTURE OF THE POLYZOA.

The Polyzoa constitute a class in the third great division of the animal
kingdom, the so-called Triploblastea. In this division are included also
the worms, molluscs, insects, crustacea, spiders, vertebrates, etc.; for
heterogeneous as its elements appear, all these animals may be
considered to have essential features in common, in particular a body
consisting primarily of three cellular layers. Most of them also possess
a body cavity distinct from the alimentary canal. Some authors regard
the position of the polyzoa as near that of the higher worms, but the
group is an isolated one.

In considering the anatomy of simple forms of animal life such as the
sponges it is necessary to pay attention mainly to individual cells, but
in discussing more complicated forms our notice is first attracted to
tissues and organs, for the cells of which these tissues and organs are
composed have each a definite position, a definite structure, and a
definite function. The most characteristic feature of the polyzoa,
considered from this point of view, is the fact that most of their
organs fall into one of two categories and are connected either with
what is called the "zooecium" or with what is known as the "polypide."
The zooecium is a cage in which the polypide is enclosed, but it is a
living cage, differing from the shell of a snail or the tubes in which
many worms encase themselves in being part of the animal itself. The
polypide consists mainly of the organs connected directly and indirectly
with nutrition and of part of the muscular system; its name is derived
from the fact that it bears a superficial resemblance to a polyp such as
_Hydra_.

The shape and structure of the zooecium differs greatly in different
groups of polyzoa. In its simplest form it is merely a cylindrical tube
of living matter which secretes an outer horny or gelatinous covering.
It is open at the end furthest from its base, at which it is attached
either to another zooecium or to some kind of supporting structure.
Certain parts of the polypide can always be extruded from the aperture,
which is known technically as the "orifice," or withdrawn through it
into the zooecium. When the polypide is retracted it draws in with it a
portion of the zooecium. The dead outer layer or ectocyst lines part of
the portion thus invaginated and forms the walls of a cavity within the
orifice. The base of this cavity consists in many forms of a transverse
partition pierced in the middle by a circular hole and known as the
"diaphragm." The diaphragm, however, does not constitute the limit of
the invaginated portion of the zooecium, for the living inner wall or
endocyst is dragged in still further and forms a sheath round the
retracted tentacles. When the tentacles are protruded they emerge
through the hole in the diaphragm, carrying with them their sheath of
endocyst. The invagination above the diaphragm, consisting of both
endocyst and ectocyst, is then everted.

The tentacles are a characteristic feature of the polypide. Together
with the base to which they are attached they are known as the
"lophophore"; they surround the mouth, usually in a circle. They differ
widely from the tentacles of _Hydra_ in both structure and function,
although they too serve as organs for the capture of prey; they are not
highly contractile and are not provided with nettle-cells but are
covered with cilia, which are in constant motion. When extruded they
form a conspicuous calix-like crown to the zooecium, but in the
retracted condition they are closely pressed together and lie parallel
to one another. They are capable individually of motion in all
directions but, although they usually move in concert, they cannot as a
rule seize objects between them.

The mouth is a hole situated in the midst of the tentacles. It leads
directly into a funnel-shaped oesophagus, the upper part of which is
lined with cilia and is sometimes distinguished as the "pharynx," while
the lower part, the oesophagus proper, is a thin-walled tube that
connects the pharynx with the stomach, which it enters on the dorsal
side. The stomach is a bulky organ that differs markedly in form and
structure in different groups of polyzoa. It is lined internally with
glandular cells and the inner wall is sometimes thrown into folds or
"rugæ." The part with which the oesophagus communicates is known as the
"cardiac" portion, while the part whence the intestine originates is
called the "pylorus" or "pyloric" portion. The intestine commences on
the ventral side opposite the entrance of the oesophagus and nearly on a
level with it, the bulk of the stomach depending between the two tubes.
This part of the stomach is often produced into a blind tube, the fundus
or cæcum. The alimentary canal may therefore be described as distinctly
Y-shaped. The proximal part of the intestine is in some forms lined with
cilia, and the tube as a whole is usually divided into two parts--the
intestine proper, which is nearest the stomach, and the rectum, which
opens by the anus not far from the mouth.

The nervous system consists of a central ganglion or brain, which is
situated at the base of the tentacles on the side nearest the anus and
gives out radiating nerves in all directions. Close to the brain and
providing a communication between the cavity of the zooecium and the
cavity in which the tentacles are contained (or, in the case of an
expanded polyp, the external world) is a ciliated tube known as the
"intertentacular organ." Apparently it acts as a passage through which
the genital products are expelled; but contradictory statements have
been made regarding it, and perhaps it is present only at certain
seasons or in certain conditions of the polypide.

[Illustration: Fig. 30.--Vertical section through a polypide of
_Alcyonidium_ with the polypide retracted (after Prouho).

A=orifice; B=contracted collar; C=diaphragm; D=parieto-vaginal muscles;
E=tentacles; F=pharynx; G=oesophagus; H=stomach; J=intestine; K=rectum;
L=intertentacular organ; M=retractor muscle; N=testes; O=ovary;
P=funiculus; Q=parietal muscles; R=ectocyst; S=endocyst.]

The muscular system is often of a complicated nature, but three sets of
muscles may be distinguished as being of peculiar importance, viz., (i)
the retractor muscles, which are fixed to the base of the lophophore at
one end and to the base of the zooecium at the other, and by contracting
pull the former back into the zooecium; (ii) the parieto-vaginal
muscles, which connect the upper part of the invaginated portion of the
zooecium with the main wall thereof; and (iii) the parietal muscles,
which run round the inner wall of the zooecium and compress the zooecium
as a whole. The parietal muscles are not developed in the
Phylactolæmata, the most highly specialized group of freshwater polyzoa.

The cavity between the polypide and the zooecium contains a reticulate
tissue of cells known as the "funicular" tissue, and this tissue is
usually concentrated to form a hollow strand or strands ("funiculi")
that connect the outer wall of the alimentary canal with the endocyst.

This rapid sketch of the general anatomy of a simple polyzoon will be
the best understood by comparing it with fig. 30, which represents, in a
somewhat diagrammatic fashion, a vertical section through a single
zooecium and polypide of the order Ctenostomata, to which some of the
freshwater species belong. The polypide is represented in a retracted
condition in which the Y-shaped disposition of the alimentary canal is
somewhat obscured.

In the great majority of cases the polyzoa form permanent colonies or
polyparia, each of which consists of a number of individual zooecia and
polypides connected together by threads of living tissue. These colonies
are formed by budding, not by independent individuals becoming
associated together. In a few cases compound colonies are formed owing
to the fact that separate simple colonies congregate and secrete a
common investment; but in these cases there is no organic connection
between the constituent colonies. It is only in the small subclass
Entoprocta, the polypides and zooecia of which are not nearly so
distinct from one another as they are in other polyzoa (the Ectoprocta),
that mature solitary individuals occur.

As representatives of both subclasses of polyzoa and of more than one
order of Ectoprocta occur in fresh water, I have prefaced my description
of the Indian species with a synopsis of the more conspicuous characters
of the different groups (pp. 183-186).


CAPTURE AND DIGESTION OF FOOD: ELIMINATION OF WASTE PRODUCTS.

The food of all polyzoa consists of minute living organisms, but its
exact nature has been little studied as regards individual species and
genera. In _Victorella bengalensis_ it consists largely of diatoms,
while the species of _Hislopia_ and _Arachnoidea_ possess an alimentary
canal modified for the purpose of retaining flagellate organisms until
they become encysted. Similar organisms form a large part of the food of
the phylactolæmata.

Although the tentacles may be correctly described as organs used in
capturing prey, they do not themselves seize it but waft it by means of
the currents set up by their cilia to the mouth, into which it is swept
by the currents produced by the cilia lining the pharynx. The tentacles
are also able in some species to interlace themselves in order to
prevent the escape of prey. Apparently they have the power of rejecting
unsuitable food, for they may often be observed to bend backwards and
forwards and thrust particles that have approached them away, and if the
water contains anything of a noxious nature in solution the lophophore
is immediately retracted, unless it has been completely paralysed. In
the phylactolæmata the peculiar organ known as the epistome is capable
of closing the mouth completely, and probably acts as an additional
safeguard in preventing the ingestion of anything of an injurious
nature.

In many genera and larger groups the food commonly passes down the
pharynx into the stomach without interruption, although it is probable
that in all species the oesophagus can be closed off from the stomach by
a valve at its base. In some forms, however, a "gizzard" is interposed
between the oesophagus and the stomach. This gizzard has not the same
function in all cases, for whereas in some forms (_e. g._, in
_Bowerbankia_) it is lined with horny projections and is a powerful
crushing organ, in others (_e. g._, in _Hislopia_ or _Victorella_) it
acts as an antechamber in which food can be preserved without being
crushed until it is required for digestion, or rough indigestible
particles can be retained which would injure the delicate walls of the
stomach.

Digestion takes place mainly in the stomach, the walls of which are of a
glandular nature. The excreta are formed into oval masses in the rectum
and are extruded from the anus in this condition.

Although the gross non-nutritious parts of the food are passed _per
anum_, the waste products of the vital processes are not eliminated so
easily, and a remarkable process known as the formation of brown bodies
frequently takes place. This process cannot be described more clearly
and succinctly than by quoting Dr. Harmer's description of it from pp.
471 and 472 of vol. ii. of the Cambridge Natural History, a volume to
which I have been much indebted in the preparation of this introduction.
The description is based very largely on Dr. Harmer's own
observations[AW].

     [Footnote AW: Q. J. Micr. Sci. xxxiii, p. 123 (1892).]

"The tentacles, alimentary canal, and nervous system break down, and the
tentacles cease to be capable of being protruded. The degenerating
organs become compacted into a rounded mass, known from its colour as
the 'brown body.' This structure may readily be seen in a large
proportion of the zooecia of transparent species. In active parts of the
colony of the body-wall next develops an internal bud-like structure,
which rapidly acquires the form of a new polypide. This takes the place
originally occupied by the old polypide, while the latter may either
remain in the zooecium in the permanent form of a 'brown body,' or pass
to the exterior. In _Flustra_ the young polypide-bud becomes connected
with the 'brown body' by a funiculus. The apex of the blind pouch or
'cæcum' of the young stomach is guided by this strand to the 'brown
body,' which it partially surrounds. The 'brown body' then breaks up,
and its fragments pass into the cavity of the stomach, from which they
reach the exterior by means of the anus."

Brown bodies are rarely if ever found in the phylactolæmata, in which
the life of the colony is always short; but they are not uncommon in
_Hislopia_ and _Victorella_, although in the case of the former they may
easily escape notice on account of the fact that they are much paler in
colour than is usually the case. When they are found in a ctenostome the
collar-like membrane characteristic of the suborder is extruded from the
orifice (which then disappears) and remains as a conspicuous external
addition to the zooecium, the ectocyst of which, at any rate in
_Bowerbankia_ and _Victorella_, sometimes becomes thickened and dark in
colour.

It is noteworthy that the colouring matter of the brown bodies is
practically the only colouring matter found in the polypides of most
polyzoa. Young polypides are practically colourless in almost all cases.


REPRODUCTION: BUDDING.

Polyzoa reproduce their species in three ways--(i) by means of eggs,
(ii) by budding, and (iii) by means of bodies developed asexually and
capable of lying dormant in unfavourable conditions without losing their
vitality.

Most, if not all species are hermaphrodite, eggs and spermatozoa being
produced either simultaneously or in succession by each individual, or
by certain individuals in each zoarium. The reproductive organs are
borne on the inner surface of the endocyst, as a rule in a definite
position, and often in connection with the funiculus or funiculi. It is
doubtful to what extent eggs are habitually fertilized by spermatozoa of
the individual that has borne them, but in some cases this is
practically impossible and spermatozoa from other individuals must be
introduced into the zooecium.

Budding as a rule does not result in the formation of independent
organisms, but is rather comparable to the proliferation that has become
the normal method of growth in sponges, except of course that
individuality is much more marked in the component parts of a polyzoon
colony than it is in a sponge. In the genera described in this volume
budding takes place by the outgrowth of a part of the body-wall and the
formation therein of a new polypide, but the order in which the buds
appear and their arrangement in reference to the parent zooecium is
different in the different groups. In the freshwater ctenostomes three
buds are typically produced from each zooecium, one at the anterior end
and one at either side, the two latter being exactly opposite one
another. The parent zooecium in this formation arises from another
zooecium situated immediately behind it, so that each zooecium, except
at the extremities of the zoarium, is connected with four other zooecia,
the five together forming a cross. The two lateral buds are, however,
frequently suppressed, or only one of them is developed, and a linear
series of zooecia with occasional lateral branches is formed instead of
a series of crosses. In the phylactolæmata, on the other hand, the
linear method of budding is the typical one, but granddaughter-buds are
produced long before the daughter-buds are mature, so that the zooecia
are frequently pressed together, and lateral buds are produced
irregularly. In _Victorella_ additional adventitious buds are produced
freely near the tip of the zooecium.

Reproduction by spontaneous fission sometimes occurs, especially in the
Lophopinæ, but the process differs from that which takes place when a
_Hydra_ divides into two, for there is no division of individual zooecia
or polypides but merely one of the whole zoarium.

The production of reproductive bodies analogous to the gemmules of
sponges appears to be confined in the polyzoa to the species that
inhabit fresh or brackish water, nor does it occur in all of these.

All the phylactolæmata produce, within their zooecia, the bodies known
as statoblasts. These bodies consist essentially of masses of cells
containing abundant food-material and enclosed in a capsule with thick
horny walls. In many cases the capsule is surrounded by a "swim-ring"
composed of a mass of horny-walled chambers filled with air, which
renders the statoblast extremely light and enables it to float on the
surface of the water; while in some genera the margin of the swim-ring
bears peculiar hooked processes, the function of which is obscure. The
whole structure first becomes visible as a mass of cells (the origin of
all of which is not the same) formed in connection with the funiculus,
and the statoblast may be regarded as an internal bud. Its origin and
development in different genera has been studied by several authors,
notably by Oka[AX] in _Pectinatella_, and by Braem[AY] in _Cristatella_.

     [Footnote AX: Journ. Coll. Sci. Tokyo, iv, p. 124 (1891).]

     [Footnote AY: Bibliotheca Zoologica, ii, pt. 6, p. 17
     (1890).]

The external form of the statoblasts is very important in the
classification of the phylactolæmata, to which these structures are
confined. In all the genera that occur in India they are flattened and
have an oval, circular, or approximately oval outline.

In temperate climates statoblasts are produced in great profusion at the
approach of winter, but in India they occur, in most species, in
greatest numbers at the approach of the hot weather.

[Illustration: Fig. 31.--Part of the zoarium of _Victorella bengalensis_
entirely transformed into resting buds, × 25. (From an aquarium in
Calcutta.)]

In the family Paludicellidæ (ctenostomata) external buds which resemble
the statoblasts in many respects are produced at the approach of
unfavourable climatic conditions, but no such buds are known in the
family Hislopiidæ, the zoaria of which appear to be practically
perennial. The buds consist of masses of cells formed at the points at
which ordinary buds would naturally be produced, but packed with
food-material and protected like statoblasts by a thick horny coat. It
seems also that old zooecia and polypides are sometimes transformed into
buds of the kind (fig. 31), and it is possible that there is some
connection between the formation of brown bodies and their production.
Like the statoblasts of the phylactolæmata the resting buds of the
Paludicellidæ are produced in Europe at the approach of winter, and in
India at that of the hot weather.


DEVELOPMENT.

(a) _From the Egg._

Some polyzoa are oviparous, while in others a larva is formed within the
zooecium and does not escape until it has attained some complexity of
structure. Both the ctenostomatous genera that are found in fresh water
in India are oviparous, but whereas in _Victorella_ the egg is small and
appears to be extruded soon after its fertilization, in _Hislopia_ it
remains in the zooecium for a considerable time, increases to a
relatively large size, and in some unknown manner accumulates a
considerable amount of food-material before escaping. Unfortunately the
development is unknown in both genera.

In the phylactolæmata the life-history is much better known, having been
studied by several authors, notably by Allman, by Kraepelin, and by
Braem (1908). The egg is contained in a thin membrane, and while still
enclosed in the zooecium, forms by regular division a hollow sphere
composed of similar cells. This sphere then assumes an ovoid form,
becomes covered with cilia externally, and breaks its way through the
egg-membrane into the cavity of the zooecium. Inside the embryo, by a
process analogous to budding, a polypide or a pair of polypides is
formed. Meanwhile the embryo has become distinctly pear-shaped, the
polypide or polypides being situated at its narrow end, in which a pore
makes its appearance. The walls are hollow in the region occupied by the
polypide, the cavity contained in them being bridged by slender threads
of tissue. The larva thus composed makes its way out of the zooecium,
according to Kraepelin through the orifice of a degenerate bud formed
for its reception, and swims about for a short time by means of the
cilia with which it is covered. Its broad end then affixes itself to
some solid object, the polypide is everted through the pore at the
narrow end and the whole of that part of the larva which formerly
enclosed it is turned completely inside out. A zoarium with its included
polypides is finally produced from the young polypide by the rapid
development of buds.

(b) _From the Statoblast and Resting Buds._

There is little information available as regards the development of the
young polyzoon in the resting buds of the freshwater ctenostomes. In
_Paludicella_ and _Pottsiella_ the capsule of the bud splits
longitudinally into two valves and the polypide emerges between them;
but in _Victorella bengalensis_ one of the projections on the margin of
the bud appears to be transformed directly into the tip of a new
zooecium and the capsule is gradually absorbed.

Contradictory statements have been made as regards several important
points in the development of the statoblast and it is probable that
considerable differences exist in different species. The following facts
appear to be of general application. The cellular contents of the
capsule consist mainly of a mass of cells packed with food-material in a
granular form, the whole enclosed in a delicate membrane formed of flat
cells. When conditions become favourable for development a cavity
appears near one end of the mass and the cells that form its walls
assume a columnar form in vertical section. The cavity increases rapidly
in size, and, as it does so, a young polypide is budded off from its
walls. Another bud may then appear in a similar fashion, and the
zooecium of the first bud assumes its characteristic features. The
capsule then splits longitudinally into two disk-like valves and the
young polypide, in some cases already possessing a daughter bud, emerges
in its zooecium, adheres by its base to some external object and
produces a new polyparium by budding. The two valves of the statoblast
often remain attached to the zoarium that has emerged from between them
until it attains considerable dimensions (see Plate IV, fig. 3 _a_).

What conditions favour development is a question that cannot yet be
answered in a satisfactory manner. Statoblasts can lie dormant for
months and even for years without losing their power of germinating, and
it is known that in Europe they germinate more readily after being
subjected to a low temperature. In tropical India this is, of course, an
impossible condition, but perhaps an abnormally high temperature has the
same effect. At any rate it is an established fact that whereas the
gemmules of most species germinate in Europe in spring, in Bengal they
germinate either at the beginning of the "rains" or at that of our mild
Indian winter.


MOVEMENTS.

[Illustration: Fig. 32.--Zoarium of _Lophopodella carteri_ moving along
the stem of a water plant, × 4. (From Igatpuri Lake.)]

In the vast majority of the polyzoa, marine as well as freshwater,
movement is practically confined to the polypide, the external walls of
the zooecium being rigid, the zooecia being closely linked together and
the whole zoarium permanently fixed to some extraneous object. In a few
freshwater species belonging to the genera _Cristatella_, _Lophopus_,
_Lophopodella_ and _Pectinatella_, the whole zoarium has the power of
progression. This power is best developed in _Cristatella_, which glides
along with considerable rapidity on a highly specialized "sole" provided
with abundant mucus and representing all that remains of the ectocyst.
It is by no means clear how the zoaria of the other genera move from one
place to another, for the base is not modified, so far as can be seen,
for the purpose, and the motion is extremely slow. It is probable,
however, that progression is effected by alternate expansions and
contractions of the base, and in _Lophopodella_ (fig. 32), which moves
rather less slowly than its allies, the anterior part of the base is
raised at times from the surface along which it is moving. The whole
zoarium can be released in this way and occasionally drops through the
water, and is perhaps carried by currents from one place to another in
so doing.

So far as the polypides are concerned, the most important movements are
those which enable the lophophore and the adjacent parts to be extruded
from and withdrawn into the zooecium. The latter movement is executed by
means of the retractor muscles, which by contracting drag the extruded
parts back towards the posterior end of the endocyst, but it is not by
any means certain how the extrusion of the lophophore is brought about.
In most ctenostomes the action of the parietal muscles doubtless assists
in squeezing it out when the retractor and parieto-vaginal muscles
relax, but Oka states that protrusion can be effected in the
phylactolæmata even after the zooecium has been cut open. Possibly some
hydrostatic action takes place, however, and allowance must always be
made for the natural resilience of the inverted portion of the ectocyst.

Even when the polypide is retracted, muscular action does not cease, for
frequent movements, in some cases apparently rhythmical, of the
alimentary canal may be observed, and in _Hislopia_ contraction of the
gizzard takes place at irregular intervals.

When the lophophore is expanded, the tentacles in favourable
circumstances remain almost still, except for the movements of their
cilia; but if a particle of matter too large for the mouth to swallow or
otherwise unsuitable is brought by the currents of the cilia towards it,
individual tentacles can be bent down to wave it away and similar
movements are often observed without apparent cause.

In the cheilostomes certain individuals of each zoarium are often
profoundly modified in shape and function and exhibit almost constant
rhythmical or convulsive movements, some ("avicularia") being shaped
like a bird's beak and snapping together, others ("vibracula") being
more or less thread-like and having a waving motion.


DISTRIBUTION OF THE FRESHWATER POLYZOA.

Fifteen genera of freshwater Polyzoa are now recognized, one
entoproctous and fourteen ectoproctous; five of the latter are
ctenostomatous and nine phylactolæmatous. Of the fourteen ectoproctous
genera seven are known to occur in India, viz., _Victorella_,
_Hislopia_, _Fredericella_, _Plumatella_, _Stolella_, _Lophopodella_,
and _Pectinatella_. Except _Stolella_, which is only known from northern
India, these genera have an extremely wide geographical range;
_Victorella_ occurs in Europe, India, Africa, and Australia; _Hislopia_
in India, Indo-China, China, and Siberia; _Fredericella_ in Europe, N.
America, Africa, India, and Australia; _Plumatella_ in all geographical
regions; _Lophopodella_ in E. and S. Africa, India, and Japan;
_Pectinatella_ in Europe, N. America, Japan, and India.

Two genera, _Paludicella_ and _Lophopus_, have been stated on
insufficient grounds to occur in India. The former is known from Europe
and N. America, and is said to have been found in Australia, while the
latter is common in Europe and N. America and also occurs in Brazil.

Of the genera that have not been found in this country the most
remarkable are _Urnatella_ and _Cristatella_. The former is the only
representative in fresh water of the Entoprocta and has only been found
in N. America. Each individual is borne upon a segmented stalk the
segments of which are enclosed in strong horny coverings and are
believed to act as resting buds. _Cristatella_, which is common in
Europe and N. America, is a phylactolæmatous genus of highly specialized
structure. It possesses a creeping "sole" or organ of progression at the
base of the zoarium.

The other phylactolæmatous genera that do not occur in India appear to
be of limited distribution, for _Australella_ is only known from N. S.
Wales, and _Stephanella_ from Japan. The ctenostomatous _Arachnoidea_
has only been reported from Lake Tanganyika, and _Pottsiella_ only from
a single locality in N. America.

As regards the exotic distribution of the Indian species little need be
said. The majority of the _Plumatellæ_ are identical with European
species, while the only species of _Fredericella_ that has been
discovered is closely allied to the European one. The Indian species of
_Lophopodella_ occurs also in E. Africa and Japan, while that of
_Pectinatella_ is apparently confined to India, Burma and Ceylon, but is
closely allied to a Japanese form.


POLYZOA OF BRACKISH WATER.

With the exception of _Victorella_, which occurs more commonly in
brackish than in fresh water and has been found in the sea, the genera
that occur in fresh water are confined or practically confined to that
medium; but certain marine ctenostomes and cheilostomes not uncommonly
make their way, both in Europe and in India, into brackish water, and in
the delta of the Ganges an entoproctous genus also does so. The
ctenostomatous genera that are found occasionally in brackish water
belong to two divisions of the suborder, the Vesicularina and the
Alcyonellea. To the former division belongs _Bowerbankia_, a form of
which (_B. caudata_ subsp. _bengalensis_, p. 187) is often found in the
Ganges delta with _Victorella bengalensis_. No species of Alcyonellea
has, however, as yet been found in Indian brackish waters. The two
Indian cheilostomes of brackish water belong to a genus (_Membranipora_)
also found in similar situations in Europe. One of them (_M.
lacroixii_[AZ]) is, indeed, identical with a European form that occurs
in England both in the sea and in ditches of brackish water. I have
found it in the Cochin backwaters, in ponds of brackish water at the
south end of the Chilka Lake (Ganjam, Madras), on the shore at Puri in
Orissa, and in the Mutlah River at Port Canning. The second species (_M.
bengalensis_, Stoliczka) is peculiar to the delta of the Ganges[BA] and
has not as yet been found in the open sea. The two species are easily
recognized from one another, for whereas the lip of _M. bengalensis_
(fig. 33) bears a pair of long forked spines, there are no such
structures on that of _M. lacroixii_, the dorsal surface of which is
remarkably transparent. _M. lacroixii_ forms a flat zoarium, the only
part visible to the naked eye being often the beaded margin of the
zooecia, which appears as a delicate reticulation on bricks, logs of
wood, the stems of rushes and of hydroids, etc.; but the zoarium of _M.
bengalensis_ is as a rule distinctly foliaceous and has a peculiar
silvery lustre.

     [Footnote AZ: There is some doubt as to the proper name of
     this species, which may not be the one originally described
     as _Membranipora lacroixii_ by Andouin. I follow Busk and
     Hincks in my identification (see Cat. Polyzoa Brit. Mus. ii,
     p. 60, and Hist. Brit. Polyzoa, p. 129). Levinsen calls it
     _M. hippopus_, sp. nov. (see Morphological and Systematic
     Studies on the Cheilostomatous Bryozoa, p. 144; Copenhagen,
     1909).]

     [Footnote BA: Miss Thornely (Rec. Ind. Mus. i, p. 186, 1907)
     records it from Mergui, but this is an error due to an
     almost illegible label. The specimens she examined were the
     types of the species from Port Canning. Since this was
     written I have obtained specimens from Bombay--_April_,
     1911.]

[Illustration: Fig. 33.--Outline of four zooecia of _Membranipora
bengalensis_, Stoliczka (from type specimen, after Thornely). In the
left upper zooecium the lip is shown open.]

_Loxosomatoides_[BB] (fig. 34), the Indian entoproctous genus found in
brackish water, has not as yet been obtained from the open sea, but has
recently been introduced, apparently from a tidal creek, into isolated
ponds of brackish water at Port Canning. It is easily recognized by the
chitinous shield attached to the ventral (posterior) surface.

     [Footnote BB: Annandale, Rec. Ind. Mus. ii, p. 14 (1908).]

[Illustration: Fig. 34.--_Loxosomatoides colonialis_, Annandale.

A and B, a single individual of form A, as seen (A) in lateral, and (B)
in ventral view; C, outline of a similar individual with the tentacles
retracted, as seen from in front (dorsal view); D, ventral view of an
individual and bud of form B. All the figures are from the type
specimens and are multiplied by about 70.]


II.

HISTORY OF THE STUDY OF THE FRESHWATER POLYZOA.

The naturalists of the eighteenth century were acquainted with more than
one species of freshwater polyzoon, but they did not distinguish these
species from the hydroids. Trembley discovered _Cristatella_, which he
called "Polype à Panache," in 1741, and Linné described a species of
_Plumatella_ under the name _Tubipora repens_ in 1758, while ten years
later Pallas gave a much fuller description (under the name _Tubularia
fungosa_) of the form now known as _Plumatella fungosa_ or _P. repens_
var. _fungosa_. Although Trembley, Baker, and other early writers on the
fauna of fresh water published valuable biological notes, the first
really important work of a comprehensive nature was that of Dumortier
and van Beneden, published in 1848. All previous memoirs were, however,
superseded by Allman's Monograph of the Fresh-Water Polyzoa, which was
issued in 1857, and this memoir remains in certain respects the most
satisfactory that has yet been produced. In 1885 Jullien published a
revision of the phylactolæmata and freshwater ctenostomes which is
unfortunately vitiated by some curious lapses in observation, but it is
to Jullien that the recognition of the proper position of _Hislopia_ is
due. The next comprehensive monograph was that of Kraepelin, which
appeared in two parts (1887 and 1892) in the Abhandlungen des Naturwiss.
Vereins of Hamburg. In its detailed information and carefully executed
histological plates this work is superior to any that preceded it or has
since appeared, but the system of classification adopted is perhaps less
liable to criticism than that followed by Braem in his "Untersuchungen,"
published in the Bibliotheca Zoologica in 1888.

During the second half of the nineteenth century and the first decade of
the twentieth several authors wrote important works on the embryology
and anatomy of the phylactolæmata, notably Kraepelin, Braem, and Oka;
but as yet the ctenostomes of fresh water have received comparatively
little attention from anything but a systematic point of view.

From all points of view both the phylactolæmata and the ctenostomes of
Asia have been generally neglected, except in the case of the Japanese
phylactolæmata, which have been studied by Oka. Although Carter made
some important discoveries as regards the Indian forms, he did not
devote to them the same attention as he did to the sponges. In the case
of the only new genus he described he introduced a serious error into
the study of the two groups by placing _Hislopia_ among the
cheilostomes, instead of in its true position as the type genus of a
highly specialized family of ctenostomes.

For fuller details as to the history of the study of the freshwater
Polyzoa the student may refer to Allman's and to Kraepelin's monographs.
An excellent summary is given by Harmer in his chapter on the freshwater
Polyzoa in vol. ii. of the Cambridge Natural History; and Loppens has
recently (1908) published in the Annales de Biologie lacustre a concise
survey of the systematic work that has recently been undertaken.
Unfortunately he perpetuates Carter's error as regards the position of
_Hislopia_.


BIBLIOGRAPHY OF THE FRESHWATER POLYZOA.

A very full bibliography of the freshwater Polyzoa will be found in pt.
i. of Kraepelin's "Die Deutschen Süsswasserbryozoen" (1887), while
Loppens, in his survey of the known species (Ann. Biol. lacustre, ii,
1908), gives some recent references. The following list contains the
titles of some of the more important works of reference, of memoirs on
special points such as reproduction and of papers that have a special
reference to Asiatic species. Only the last section is in any way
complete.

(a) _Works of Reference._

1847. VAN BENEDEN, "Recherches sur les Bryozoaires fluviatiles de
Belgique," Mém. Ac. Roy. Belgique, xxi.

1850. DUMORTIER and VAN BENEDEN, "Histoire Naturelle des Polypes
composés d'eau douce," 2^e partie, Mém. Ac. Roy. Bruxelles, xvi
(complément).

1856. ALLMAN, "A Monograph of the Fresh-Water Polyzoa" (London).

1866-1868. HYATT, "Observations on Polyzoa, suborder Phylactolæmata,"
Comm. Essex Inst. iv, p. 197, v, p. 97.

1880. HINCKS, "A History of the British Marine Polyzoa."

1885. JULLIEN, "Monographie des Bryozoaires d'eau douce," Bull. Soc.
zool. France, x, p. 91.

1887 & 1892. KRAEPELIN, "Die deutschen Süsswasserbryozoen," Abhandl.
Nat. Vereins Hamburg, x & xii.

1890. BRAEM, "Untersuchungen des Bryozoen des süssen Wassers," Bibl.
Zool. ii, Heft 6 (Cassel).

1896. HARMER, Cambridge Natural History, ii, Polyzoa, chap. xviii.

1899. KORSCHELT and HEIDER, "Embryology of Invertebrates," vol. ii,
chap. xvi. (English edition by Bernard and Woodward, 1899.)

1908. LOPPENS, "Les Bryozoaires d'eau douce," Ann. Biol. lacustre, iii.
p. 141.

(b) _Special Works on Embryology, etc._

1875. NITSCHE, "Beiträge zur Kenntniss der Bryozoen," Zeitschr. f. wiss.
Zool. xxv (supplement), p. 343.

1880. REINHARD, "Zur Kenntniss der Süsswasser-Bryozoen," Zool. Anz. iii,
p. 208.

1888. BRAEM, "Untersuchungen über die Bryozoen des süssen Wassers,"
Zool. Anz. xi, pp. 503, 533.

1891. OKA, "Observations on Freshwater Polyzoa," J. Coll. Sci. Tokyo,
iv, p. 89.

1906. WILCOX, "Locomotion in young colonies of _Pectinatella
magnifica_," Biol. Bull. Wood's Hole, ii.

1908. BRAEM, "Die geschlechtliche Entwickelung von Fredericella sultana
nebst Beobachtungen über die weitere Lebensgeschichte der Kolonien,"
Bibl. Zool. xx, Heft 52.

(c) _Papers that refer specifically to Asiatic species._

1851. LEIDY described _Plumatella diffusa_ in Proc. Ac. Philad. v, p.
261 (1851).

1858. CARTER, "Description of a Lacustrine Bryozoon allied to
_Flustra_," Ann. Nat. Hist. (3) i, p. 169.

1859. CARTER, "On the Identify in Structure and Composition of the
so-called Seed-like Body of _Spongilla_ with the Winter-egg of the
Bryozoa: and the presence of Starch-granules in each," Ann. Nat. Hist.
(3) iii, p. 331. (Statoblast of _Lophopodella_ described and figured.)

1862. MITCHELL, "Freshwater Polyzoa," Q. J. Micr. Sci. (new series) ii,
p. 61. ("_Lophopus_" recorded from Madras.)

1866. HYATT, "Observations on Polyzoa, suborder Phylactolæmata," Comm.
Essex Inst. iv, p. 197. ("_Pectinatella carteri_" named.)

1869. STOLICZKA, "On the Anatomy of _Sagartia schilleriana_ and
_Membranipora bengalensis_, a new coral and a bryozoon living in
brackish water at Port Canning," J. As. Soc. Bengal, xxxviii, ii, p. 28.

1880. JULLIEN, "Description d'un nouveau genre de Bryozoaire
Cheilostomien des eaux douces de la Chine et du Cambodge et de deux
espèces nouvelles," Bull. Soc. zool. France, v, p. 77. ("_Norodonia_"
described.)

1885. JULLIEN, "Monographie des Bryozoaires d'eau douce," Bull. Soc.
zool. France, x, p. 91. (_Hislopia_ assigned to the ctenostomes.)

1887. KRAEPELIN, "Die deutschen Süsswasserbryozoen," Abh. Ver. Hamburg,
x. (_Plumatella philippinensis._)

1891. OKA, "Observations on Freshwater Polyzoa," J. Coll. Sci. Tokyo,
iv, p. 89.

1898. MEISSNER, "Die Moosthiere Ost-Afrikas," in Mobius's
Deutsch-Ost-Afrika, iv. (_Lophopodella carteri_ recorded from E.
Africa.)

1901. KOROTNEFF, "Faunistische Studien am Baikalsee," Biol. Centrbl.
xxi, p. 305. ("_Echinella_" described.)

1904-1906. ROUSSELET, "On a new Freshwater Polyzoon from Rhodesia,
_Lophopodella thomasi_, gen. et sp. nov.", J. Quekett Club (2) ix, p.
45. (Genus _Lophopodella_ described.)

1906. ANNANDALE, "Notes on the Freshwater Fauna of India. No. II. The
Affinities of _Hislopia_," J. As. Soc. Bengal (new series) ii, p. 59.

1906. KRAEPELIN, "Eine Süsswasser-bryozoë (_Plumatella_) aus Java,"
Mitth. Mus. Hamburg, xxiii, p. 143.

1907. ANNANDALE, "Notes on the Freshwater Fauna of India. No. XII. The
Polyzoa occurring in Indian Fresh and Brackish Pools," J. As. Soc. Bengal
(new series) iii, p. 83.

1907. ANNANDALE, "Statoblasts from the surface of a Himalayan Pond,"
Rec. Ind. Mus. i, p. 177.

1907. ANNANDALE, "The Fauna of Brackish Ponds at Port Canning, Lower
Bengal: I.--Introduction and Preliminary Account of the Fauna," Rec.
Ind. Mus. i, p. 35.

1907. ANNANDALE, "The Fauna of Brackish Ponds at Port Canning, Lower
Bengal: VI.--Observations on the Polyzoa, with further notes on the
Ponds," Rec. Ind. Mus. i, p. 197.

1907. ANNANDALE, "Further Note on a Polyzoon from the Himalayas," Rec.
Ind. Mus. i, p. 145.

1907. ROUSSELET, "Zoological Results of the Third Tanganyika Expedition,
conducted by Dr. W. A. Cunnington, 1904-1905.--Report on the Polyzoa,"
P. Z. Soc. London, i, p. 250. (_Plumatella tanganyikæ._)

1907. OKA, "Eine dritte Art von _Pectinatella_ (_P. davenporti_, n.
sp.)," Zool. Anz. xxxi, p. 716.

1907. APSTEIN, "Das Plancton im Colombo-See auf Ceylon," Zool. Jahrb.
(Syst.) xxv, p. 201. (_Plumatella_ recorded.)

1907. WALTON, "Notes on _Hislopia lacustris_, Carter," Rec. Ind. Mus. i,
p. 177.

1907-1908. OKA, "Zur Kenntnis der Süsswasser-Bryozoenfauna von Japan,"
Annot. Zool. Japon, vi, p. 117.

1907-1908. OKA, "Ueber eine neue Gattung von Süsserwasserbryozoen,"
Annot. Zool. Japon, vi, p. 277.

1908. ANNANDALE, "The Fauna of Brackish Ponds at Port Canning, Lower
Bengal: VII.--Further Observations on the Polyzoa with the description
of a new genus of Entoprocta," Rec. Ind. Mus. ii, p. 11.

1908. ANNANDALE, "Corrections as to the Identity of Indian
Phylactolæmata," Rec. Ind. Mus. ii, p. 110.

1908. ANNANDALE, "Three Indian Phylactolæmata," Rec. Ind. Mus. ii, p.
169.

1908. KIRKPATRICK, "Description of a new variety of _Spongilla
loricata_, Weltner," Rec. Ind. Mus. ii, p. 97. (_Hislopia_ recorded from
Burma.)

1909. ANNANDALE, "Preliminary Note on a new genus of Phylactolæmatous
Polyzoa," Rec. Ind. Mus. iii, p. 279.

1909. ANNANDALE, "A new species of _Fredericella_ from Indian Lakes,"
Rec. Ind. Mus. iii. p. 373.

1909. WALTON, "Large Colonies of _Hislopia lacustris_," Rec. Ind. Mus.
iii, p. 295.

1910. ANNANDALE, "Materials for a Revision of the Phylactolæmatous
Polyzoa of India," Rec. Ind. Mus. v, p. 37.

1911. WEST and ANNANDALE, "Descriptions of Three Species of Algæ
associated with Indian Freshwater Polyzoa," J. As. Soc. Bengal
(_ined._).




GLOSSARY OF TECHNICAL TERMS USED IN PART III.


  _Brown body_            A body formed in a zooecium by the degeneration
                          of a polypide as a preparation
                          for its regeneration.

  _Cardiac portion_ (of   That part which communicates with the
   the stomach).          oesophagus.

  _Collar_                A longitudinally pleated circular membrane
                          capable of being thrust out of the orifice
                          in advance of the lophophore and of
                          closing together inside the zooecium above
                          the tentacles when they are retracted.

  _Dorsal surface_        (_Of zooecium_ or _polypide_) the surface
                          nearest the mouth; (_of statoblast_) the
                          surface furthest from that by which the
                          statoblast is attached to the funiculus
                          during development.

  _Ectocyst_              The outer, structureless layer of the zooecium.

  _Emarginate_            Having a thin or defective triangular area
  (of a zooecium)         in the ectocyst at the tip.

  _Endocyst_              The inner, living (cellular) layer of the
                          zooecium.

  _Epistome_              A leaf-like ciliated organ that projects
                          upwards and forwards over the mouth
                          between it and the anus.

  _Funiculus_             A strand of tissue joining the alimentary
                          canal to the endocyst.

  _Furrowed_              Having a thin or defective longitudinal
  (of a zooecium)         linear streak in the ectocyst on the dorsal
                          surface.

  _Gizzard_               A chamber of the alimentary canal situated
                          at the cardiac end of the stomach and
                          provided internally with a structureless
                          lining.

  _Intertentacular organ_ A ciliated tube running between the cavity
                          of the zooecium and the external base of
                          the lophophore.

  _Keeled_                Having a longitudinal ridge on the dorsal
  (of a zooecium)         surface.

  _Lophophore_            The tentacles with the base to which they
                          are attached.

  _Marginal processes_    Chitinous hooked processes on the margin
  (of statoblast).        of the swim-ring (_q. v._).

  _OEsophagus_            That part of the alimentary canal which
                          joins the mouth to the stomach.

  _Orifice_               The aperture through which the lophophore
                          can be protruded from or retracted into
                          the zooecium.

  _Parietal muscles_      Transverse muscles running round the inner
                          wall of the zooecium.

  _Parieto-vaginal_       Muscles that surround the orifice, running
  _muscles_               between the folds of the zooecium in an
                          oblique direction.

  _Polyparium_            The whole body of zooecia and polypides
                          which are in organic connection.

  _Polypide_              The tentacular crown, alimentary canal,
                          and retractor muscles of a polyzoon-individual.

  _Pyloric portion_       That part which communicates with the
  (of the stomach).       intestine.

  _Resting bud_           An external bud provided with food-material
                          in its cells, with a horny external
                          coat and capable of lying dormant in
                          unfavourable conditions.

  _Retractor muscles_     The muscles by the action of which the
                          lophophore can be pulled back into the
                          zooecium.

  _Statoblast_            An internal bud arising from the funiculus,
                          containing food-material in its cells,
                          covered with a horny coat and capable
                          of lying dormant in unfavourable conditions.

  _Swim-ring_             A ring of polygonal air-spaces surrounding
                          the statoblast.

  _Ventral surface_       (_Of zooecium_ or _polypide_) the surface
                          nearest the anus; (_of statoblast_) the surface
                          by which the statoblast is attached
                          to the funiculus during development.

  _Zoarium_               The whole body of zooecia which are in
                          organic connection.

  _Zooecium_              Those parts of the polyzoon-individual
                          which constitute a case or "house" for
                          the polypide.




SYNOPSIS OF THE CLASSIFICATION OF THE POLYZOA.




I.

SYNOPSIS OF THE SUBCLASSES, ORDERS, AND SUBORDERS.

Class POLYZOA.

Small coelomate animals, each individual of which consists of a
polyp-like organism or polypide enclosed in a "house" or zooecium
composed partly of living tissues. The mouth is surrounded by a circle
of ciliated tentacles that can be retracted within the zooecium; the
alimentary canal, which is suspended in the zooecium, is Y-shaped and
consists of three parts, the oesophagus, the stomach, and the intestine.


Subclass ENTOPROCTA.

The anus as well as the mouth is enclosed in the circle of tentacles and
the zooecium is not very distinctly separated from the polypide. Some
forms are solitary or form temporary colonies by budding.

Most Entoprocta are marine, but a freshwater genus (_Urnatella_) occurs
in N. America, while the Indian genus _Loxosomatoides_ (fig. 34, p. 176)
is only known from brackish water.


Subclass ECTOPROCTA.

The anus is outside the circle of tentacles and the zooecium can always
be distinguished from the polypide. All species form by budding
permanent communities the individuals in which remain connected together
by living tissue.


Order I. GYMNOLÆMATA.

Ectoproctous polyzoa the polypides of which have no epistome; the
zooecia are in nearly all cases distinctly separated from one another by
transverse perforated plates.

Most of the Gymnolæmata are marine, but species belonging to two of the
three suborders into which they are divided often stray into brackish
water, while a few genera that belong to one of these two suborders are
practically confined to fresh water. The three suborders are
distinguished as follows:--


Suborder A. _CHEILOSTOMATA._

The zooecia are provided with a "lip" or lid hinged to the posterior
margin of the orifice (see fig. 33, p. 175). This lid closes
automatically outside the zooecium or in a special chamber on the
external surface (the "peristome") when the polypide retracts and is
pushed open by the tentacles as they expand. The majority of the zooecia
in each zoarium are more or less distinctly flattened, but some of them
are often modified to form "vibracula" and "avicularia."

The Cheilostomata are essentially a marine group, but some species are
found in estuaries and even in pools and ditches of brackish water (fig.
33).


Suborder B. _CTENOSTOMATA._

The zooecia are provided with a collar-like membrane which is pleated
vertically and closes together above the polypide inside the zooecium
when the former is retracted; it is thrust out of the zooecium and
expands into a ring-shaped form just before the tentacles are extruded.
The zooecia are usually more or less tubular, but in some genera and
species are flattened.

The majority of the Ctenostomata are marine, but some genera are found
in estuaries, while those of one section of the suborder live almost
exclusively in fresh water.


Suborder C. _CYCLOSTOMATA._

The zooecia are provided neither with a lip nor with a collar-like
membrane. They are tubular and usually have circular orifices.

The Cyclostomata are exclusively marine.


Order II. PHYLACTOLÆMATA.

Ectoproctous polyzoa the polypides of which have a leaf-shaped organ
called an epistome projecting upwards and forwards within the circle of
tentacles and between the mouth and the anus. The zooecia are not
distinct from one another, but in dendritic forms the zoarium is divided
irregularly by chitinous partitions.

The Phylactolæmata are, without exception, freshwater species.




II.

SYNOPSIS OF THE LEADING CHARACTERS OF THE DIVISIONS OF THE SUBORDER
CTENOSTOMATA.


Suborder B. _CTENOSTOMATA._

The suborder has been subdivided in various ways by different authors.
The system here adopted is essentially the same as that proposed in a
recent paper by Waters (Journ. Linn. Soc. London, Zool. xxi, p. 231,
1910), but I have thought it necessary to add a fourth division to the
three adopted by that author, namely, the Alcyonellea, Stolonifera, and
Vesicularina. This new division includes all the freshwater genera and
may be known as the Paludicellina. In none of these divisions are the
tentacles webbed at the base.

The four divisions may be recognized from the following synopsis of
their characteristic features:--


Division I. ALCYONELLEA.

The zooecia arise directly from one another in a fleshy or gelatinous
mass. The polypide has no gizzard. The species are essentially marine,
but a few are found in brackish water in estuaries.


Division II. STOLONIFERA.

The zooecia arise from expansions in a delicate creeping rhizome or
root-like structure, the order in which they are connected together
being more or less irregular. As a rule (perhaps always) there is no
gizzard. The species are marine.


Division III. VESICULARINA.

The zooecia grow directly from a tubular stem which is usually free and
vertical, their arrangement being alternate, spiral or irregular. There
is a stout gizzard which bears internal chitinous projections and is
tightly compressed when the polypide is retracted. The species are
essentially marine, but a few are found in brackish water.


Division IV. PALUDICELLINA, nov.

The zooecia are arranged in a regular cruciform manner and arise either
directly one from another or with the intervention of tubular processes.
If the polypide has a gizzard it does not bear internal chitinous
projections. Most of the species are confined to fresh water, but a few
are found in brackish water or even in the sea.

Although all true freshwater Ctenostomes belong to the fourth of these
divisions, species of a genus (_Bowerbankia_) included in the third are
so frequently found in brackish water and in association with one
belonging to the fourth, and are so easily confounded with the latter,
that I think it necessary to include a brief description of the said
genus and of the form that represents it in ponds of brackish water in
India.




SYSTEMATIC LIST OF THE INDIAN FRESHWATER POLYZOA.

[The types have been examined in the case of all species, etc., whose
names are marked thus, *.]


  Order I. GYMNOLÆMATA.

  Suborder I. _CTENOSTOMATA._

  [Division III. Vesicularina.]

  [Genus BOWERBANKIA, Farre (1837).]

  [_B. caudata_ subsp. _bengalensis_*, Annandale (1907).
  (Brackish water).]


  Division IV. Paludicellina, nov.

  Family I. PALUDICELLIDÆ.

  Genus 1. PALUDICELLA, Gervais (1836).

  ? _Paludicella_ sp. (_fide_ Carter).

  Genus 2. VICTORELLA, Kent (1870).

  26._V. bengalensis_*, Annandale (1907).


  Family II. HISLOPIIDÆ.

  Genus HISLOPIA, Carter (1858).

  27. _H. lacustris_, Carter (1858).
  27 _a._ _H. lacustris_ subsp. _moniliformis_*, nov.


  Order II. PHYLACTOLÆMATA.

  Division I. Plumatellina.

  Family 1. FREDERICELLIDÆ.

  Genus FREDERICELLA, Gervais (1836).

  28. _F. indica_*, Annandale (1909).


  Family 2. PLUMATELLIDÆ.

  Subfamily A. PLUMATELLINÆ.

  Genus 1. PLUMATELLA, Lamarck (1816).

  29. _P. fruticosa_, Allman (1844).
  30. _P. emarginata_, Allman (1844).
  31. _P. javanica_*, Kraepelin (1905).
  32. _P. diffusa_, Leidy (1851).
  33. _P. allmani_, Hancock (1850).
  34. _P. tanganyikæ_*, Rousselet (1907).
  35. _P. punctata_, Hancock (1850).

  Genus 2. STOLELLA, Annandale (1909).

  36. _S. indica_*, Annandale (1909).


  Subfamily B. LOPHOPINÆ.

  Genus 1. LOPHOPODELLA, Rousselet (1904).

  37. _L. carteri_* (Hyatt) (1865).
  37 _a._ _L. carteri_ var. _himalayana_* (Annandale) (1907).

  Genus 2. PECTINATELLA, Leidy (1851).

  38. _P. burmanica_*, Annandale (1908).


  Order CTENOSTOMATA.

  [Division VESICULARINA.

  Family VESICULARIDÆ.

  VESICULARIDÆ, Hincks, Brit. Marine Polyzoa, p. 512 (1880).

Zooecia constricted at the base, deciduous, attached to a stem that is
either recumbent or vertical.


Genus BOWERBANKIA, _Farre_.

     _Bowerbankia_, Farre, Phil. Trans. Roy. Soc. cxxvii, p. 391 (1837).

     _Bowerbankia_, Hincks, _op. cit._ p. 518.

_Zoarium_ vertical or recumbent. _Zooecia_ ovate or almost cylindrical,
arranged on the stem singly, in clusters or in a subspiral line.
_Polypide_ with 8 or 10 tentacles.


Bowerbankia caudata, _Hincks_.

     _Bowerbankia caudata_, Hincks, _op. cit._ p. 521, pl. lxxv,
     figs. 7, 8.

This species is easily distinguished from all others by the fact that
mature zooecia have always the appearance of being fixed to the sides of
a creeping, adherent stem and are produced, below the point at which
they are thus fixed, into a pointed "tail."


Subsp. bengalensis, _Annandale_.

     _Bowerbankia caudata_, Thornely, Rec. Ind. Mus. i, p. 196
       (1907).

     _Bowerbankia caudata_, Annandale, _ibid._ p. 203.

     _Bowerbankia caudata_ race _bengalensis_, _id._, _ibid._
       ii. p. 13 (1908).

The Indian race is only distinguished from the typical form by its
greater luxuriance of growth and by the fact that the "tail" of the
zooecia is often of relatively great length, sometimes equaling or
exceeding the rest of the zooecium. The stem, which is divided at
irregular intervals by partitions, often crosses and recrosses its own
course and even anastomoses, and a fur-like structure is formed in which
the zooecia representing the hairs become much elongated; but upright
branches are never formed. The zoarium has a greenish or greyish tinge.

TYPE in the Indian Museum.

GEOGRAPHICAL DISTRIBUTION.--_B. caudata_ subsp. _bengalensis_ is common
in brackish water in the Ganges delta, where it often occurs in close
association with _Victorella bengalensis_, and also at the south end of
the Chilka Lake in the north-east of the Madras Presidency. Although it
has not yet been found elsewhere, it probably occurs all round the
Indian coasts.]


Division PALUDICELLINA, nov.

This division consists of two very distinct families, the species of
which are easily distinguished at a glance by the fact that in one (the
Paludicellidæ) the zooecia are tubular, while in the other (the
Hislopiidæ) they are broad and flattened. The anatomical and
physiological differences between the two families are important, and
they are associated together mainly on account of the method of budding
by means of which their zoaria are produced.

[Illustration: Fig. 35.--Single zooecia of _Victorella_ and _Hislopia_
(magnified).

A, zooecium of _Victorella pavida_, Kent, with the polypide retracted
(after Kraepelin).

B, zooecium of _Hislopia lacustris_, Carter (typical form from the
United Provinces), with the collar completely and the tentacles partly
protruded.

A=collar; B=orifice; C=tentacles; D=pharynx; E=oesophagus proper;
F=gizzard; G=stomach; G'=cardiac portion of stomach; H=intestine;
J=rectum; K=anus; L=young egg; M=green cysts in gizzard; N=testes;
O=ovary; O'=funiculus.

The muscles are omitted except in fig. B.]


Family PALUDICELLIDÆ.

     PALUDICELLIDÆ, Allman, Mon. Fresh-Water Polyzoa, p. 113
     (1857).

     HOMODIÆTIDÆ, Kent, Q. J. Micr. Sci. x, p. 35 (1870).

     VICTORELLIDÆ, Hincks, Brit. Marine Polyzoa, p. 558 (1880).

     PALUDICELLIDÉES, Jullien, Bull. Soc. zool. France, x, p. 174
     (1885).

     PALUDICELLIDES, Loppens, Ann. Biol. lacustre, iii, p. 170
     (1908).

     VICTORELLIDES, _id._, _ibid._ p. 171.

_Zoarium._ The zoarium is recumbent or erect, and is formed typically
either of zooecia arising directly in cruciform formation from one
another, or of zooecia joined together in similar formation with the
intervention of tubules arising from their own bases. Complications
often arise, however, either on account of the suppression of the
lateral buds of a zooecium, so that the formation becomes linear instead
of cruciform, or by the production in an irregular manner of additional
tubules and buds from the upper part of the zooecia. A confused and
tangled zoarium may thus be formed, the true nature of which can only be
recognized by the examination of its terminal parts.

_Zooecia._ The zooecia are tubular and have a terminal or subterminal
orifice, which is angulate or subangulate as seen from above. Owing to
this fact, to the stiff nature of the external ectocyst, to the action
of circular muscles that surround the tentacular sheath, and to the
cylindrical form of the soft inverted part, the orifice, as seen from
above, appears to form four flaps or valves, thus [illustration: sketch,
similar to a cloverleaf inside a square with rounded corners].

_Polypide._ The alimentary canal is elongate and slender as a whole, the
oesophagus (including the pharynx) being of considerable length. In
_Paludicella_ and _Pottsiella_ the oesophagus opens directly into the
cardiac limb of the stomach, which is distinctly constricted at its
base; but in _Victorella_ the base of the oesophagus is constricted off
from the remainder to form an elongate oval sac the walls of which are
lined with a delicate structureless membrane. _Victorella_ may therefore
be said to possess a gizzard, but the structure that must be so
designated has not the function (that of crushing food) commonly
associated with the name, acting merely as a chamber for the retention
of solid particles. In this genus the cardiac limb of the stomach is
produced and vertical but not constricted at the base. The tentacles in
most species number 8, but in _Paludicella_ there are 16.

_Resting buds._ The peculiar structures known in Europe as "hibernacula"
are only found in this family. The name hibernacula, however, is
inappropriate to the only known Indian species as they are formed in
this country at the approach of summer instead of, as in Europe and N.
America, at that of winter. It is best, therefore, to call them "resting
buds." They consist of masses of cells congregated at the base of the
zooecia, gorged with food material and covered with a resistant horny
covering.

The family Paludicellidæ consists of three genera which may be
distinguished as follows:--

   I. Orifice terminal; main axis of the zooecium
      vertical; zooecia separated from one another
      by tubules.
    [A. Base of the zooecia not swollen; no
        adventitious buds                          POTTSIELLA.]
     B. Base of the zooecium swollen; adventitious
        buds produced near the tip                 VICTORELLA, p. 194.
  II. Orifice subterminal, distinctly on the dorsal
      surface; main axis of the zooecium horizontal
      (the zoarium being viewed from the dorsal
      surface); buds not produced at the tip of the
      zooecia                                      PALUDICELLA, p. 192.

Of these three genera, _Pottsiella_ has not yet been found in India and
is only known to occur in N. America. It consists of one species, _P.
erecta_ (Potts) from the neighbourhood of Philadelphia in the United
States.

_Victorella_ includes four species, _V. pavida_ known from England and
Germany and said to occur in Australia, _V. mülleri_ from Germany
(distinguished by possessing parietal muscles at the tip of the
zooecia), _V. symbiotica_ from African lakes and _V. bengalensis_ from
India. These species are closely related.

_Paludicella_ is stated by Carter to have been found in Bombay, but
probably what he really found was the young stage of _V. bengalensis_. A
single species is known in Europe and N. America, namely _P.
ehrenbergi_, van Beneden (=_Alcyonella articulata_, Ehrenberg).

I have examined specimens of all the species of this family as yet
known.


Genus 1. PALUDICELLA, _Gervais_.

     _Paludicella_, Gervais, Compt. Rend. iii, p. 797 (1836).

     _Paludicella_, Allman, Mon. Fresh-Water Polyzoa, p. 113
     (1857).

     ? _Paludicella_, Carter, Ann. Nat. Hist. (3) iii, p. 333
     (1859).

     _Paludicella_, Jullien, Bull. Soc. zool. France, x, p. 174
     (1885).

     _Paludicella_, Kraepelin, Deutsch. Süsswasserbryozoen, i, p.
     96 (1887).

     _Paludicella_, Loppens, Ann. Biol. lacustre, iv, p. 14
     (1910).

_Zoarium._ The nature of the zoarium in this genus is well expressed by
Ehrenberg's specific name "_articulata_," although the name was given
under a false impression. The zooecia arise directly from one another in
linear series with occasional side-branches. The side-branches are,
however, often suppressed. The zoarium as a whole is either recumbent
and adherent or at least partly vertical.

_Zooecia._ Although the zooecia are distinctly tubular as a whole, two
longitudinal axes may be distinguished in each, for the tip is bent
upwards in a slanting direction, bearing the orifice at its extremity.
The main axis is, however, at right angles to the dorso-ventral axis,
and the dorsal surface, owing to the position of the aperture, can
always be readily distinguished from the ventral, even when the position
of the zooecium is vertical. Each zooecium tapers towards the posterior
extremity. Parietal muscles are always present.

[Illustration: Fig. 36.--Structure of _Paludicella ehrenbergi_ (A and B
after Allman).

A=a single zooecium with the polypide retracted. B=the base of the
lophophore as seen from above with the tentacles removed. C=the orifice
of a polypide with the collar expanded and the tentacles partly
retracted. _a_=tentacles; _c_=collar; _d_=mouth; _e_=oesophagus;
_f_=stomach; _g_=intestine; _k_=parieto-vaginal muscles; _p_=parietal
muscles; _o_=cardiac part of the stomach; _r_=retractor muscle;
_s_=funiculus.]

_Polypide._ The most striking features of the polypide are the absence
of any trace of a gizzard and the highly specialized form assumed by the
cardiac part of the stomach. There are two funiculi, both connecting the
pyloric part of the stomach with the endocyst. The ovary develops at the
end of the upper, the testis at that of the lower funiculus.

_Resting buds._ The resting buds are spindle-shaped.

Kraepelin recognized two species in the genus mainly by their method of
growth and the number of tentacles. In his _P. mülleri_ the zoarium is
always recumbent and the polypide has 8 tentacles, whereas in _P.
articulata_ or _ehrenbergi_ the tentacles number 16 and upright branches
are usually developed. It is probable, however, that the former species
should be assigned to _Victorella_, for it is often difficult to
distinguish _Paludicella_ from young specimens of _Victorella_ unless
the latter bear adventitious terminal buds. The gizzard of _Victorella_
can be detected in well-preserved material even under a fairly low power
of the microscope, and I have examined specimens of what I believe to be
the adult of _mülleri_ which certainly belong to that genus.

It is always difficult to see the collar of _Paludicella_, because of
its transparency and because of the fact that its pleats are apparently
not strengthened by chitinous rods as is usually the case. Allman
neither mentions it in his description of the genus nor shows it in his
figures, and Loppens denies its existence, but it is figured by
Kraepelin and can always be detected in well-preserved specimens, if
they are examined carefully. If the collar were actually absent, its
absence would separate _Paludicella_ not only from _Victorella_ and
_Pottsiella_, but also from all other ctenostomes. In any case,
_Victorella_ is distinguished from _Paludicella_ and _Pottsiella_ by
anatomical peculiarities (_e. g._, the possession of a gizzard and the
absence of a second funiculus) that may ultimately be considered
sufficiently great to justify its recognition as the type and only genus
of a separate family or subfamily.

The description of _Paludicella_ is included here on account of Carter's
identification of the specimens he found at Bombay; but its occurrence
in India is very doubtful.


Genus 2. _VICTORELLA_, _Kent_.

     _Victorella_, Kent, Q. J. Micr. Sci. x, p. 34 (1870).

     _Victorella_, Hincks, Brit. Marine Polyzoa, p. 559 (1880).

     _Victorella_, Kraepelin, Deutsch. Süsswasserbryozoen, i, p.
     93 (1887).

TYPE, _Victorella pavida_, Kent.

_Zoarium._ The zoarium consists primarily of a number of erect or
semi-erect tubular zooecia joined together at the base in a cruciform
manner by slender tubules, but complications are introduced by the fact
that adventitious buds and tubules are produced, often in large numbers,
round the terminal region of the zooecia, and that these buds are often
separated from their parent zooecium by a tubule of considerable length,
and take root among other zooecia at a distance from their point of
origin. A tangled mass may thus be formed in which it is difficult to
recognize the regular arrangement of the zooecia that can be readily
detached at the growing points of the zoarium.

_Zooecia._ The zooecia when young closely resemble those of
_Paludicella_, but as they grow the terminal upturned part increases
rapidly, while the horizontal basal part remains almost stationary and
finally appears as a mere swelling at the base of an almost vertical
tube, in which by far the greater part, if not the whole, of the
polypide is contained. Round the terminal part of this tube adventitious
buds and tubules are arranged more or less regularly. There are no
parietal muscles.

_Polypide._ The polypide has 8 slender tentacles, which are thickly
covered with short hairs. The basal part of the oesophagus forms a
thin-walled sac (the "gizzard") constricted off from the upper portion
and bearing internally a thin structureless membrane. Circular muscles
exist in its wall but are not strongly developed on its upper part.
There is a single funiculus, which connects the posterior end of the
stomach with the base of the zooecium. The ovaries and testes are borne
on the endocyst, not in connection with the funiculus.

_Resting buds._ The resting buds are flattened or resemble young zooecia
in external form.

_Victorella_, although found in fresh water, occurs more commonly in
brackish water and is known to exist in the littoral zone of the sea.


26. Victorella bengalensis, _Annandale_.

     _Victorella pavida_, Annandale (_nec_ Kent), Rec. Ind. Mus.
     i, p. 200, figs. 1-4 (1907).

     _Victorella bengalensis_, _id._, _ibid._ ii, p. 12, fig. 1
     (1908).

_Zoarium._ _The mature zoarium resembles a thick fur_, the hairs of
which are represented by elongate, erect, slender tubules (the zooecia),
the arrangement of the whole being very complicated and irregular. The
base of the zoarium often consists of an irregular membrane formed of
matted tubules, which are sometimes agglutinated together by a gummy
secretion. The zoarium as a whole has a faint yellowish tinge.

_Zooecia._ The zooecia when young are practically recumbent, each being
of an ovoid form and having a stout, distinctly quadrate orificial
tubule projecting upwards and slightly forwards near the anterior margin
of the dorsal surface. At this stage a single tubule, often of great
relative length, is often given off near the orifice, bearing a bud at
its free extremity. As the zooecium grows the tubular part becomes much
elongated as compared with the basal part and assumes a vertical
position. Its quadrate form sometimes persists but more often
disappears, so that it becomes almost circular in cross-section
throughout its length. Buds are produced near the tip in considerable
profusion. As a rule, if they appear at this stage, the tubule
connecting them with the parent zooecium is short or obsolete; sometimes
they are produced only on one side of the zooecium, sometimes on two.
The buds themselves produce granddaughter and great-granddaughter buds,
often connected together by short tubules, while still small and
imperfectly developed. The swelling at the base of the zooecium, when
the latter is fully formed, is small.

_Polypide._ The polypide has the features characteristic of the genus.
The base of the gizzard is surrounded by a strong circular muscle.

[Illustration: Fig. 37.--_Victorella bengalensis_ (type specimens).

A=single zooecium without adventitious buds but with a young resting bud
(_b_), × 70 (dorsal view); B=lateral view of a smaller zooecium without
buds, × 70; C=upper part of a zooecium with a single adventitious bud, ×
70; D=outline of the upper part of a zooecium with adventitious buds of
several generations, × 35; E=remains of a zooecium with two resting buds
(_b_) attached. All the specimens figured are from Port Canning and,
except D, are represented as they appear when stained with borax carmine
and mounted in canada balsam.]

_Resting buds._ The resting buds (fig. 31, p. 170) are somewhat variable
in shape but are always flat with irregular cylindrical or
subcylindrical projections round the margin, on which the horny coat is
thinner than it is on the upper surface. This surface is either smooth
or longitudinally ridged.

TYPE in the Indian Museum.

This species differs from the European _V. pavida_ in very much the same
way as, but to a greater extent than, the Indian race of _Bowerbankia
caudata_ does from the typical English one (see p. 189). The growth of
the zoarium is much more luxuriant, and the form of the resting buds is
different.

GEOGRAPHICAL DISTRIBUTION.--_V. bengalensis_ is abundant in pools of
brackish water in the Ganges delta and in the Salt Lakes near Calcutta;
it also occurs in ponds of fresh water near the latter. I have received
specimens from Madras from Dr. J. R. Henderson, and it is probable that
the form from Bombay referred by Carter to _Paludicella_ belonged to
this species.

BIOLOGY.--In the Ganges delta _V. bengalensis_ is usually found coating
the roots and stems of a species of grass that grows in and near
brackish water, and on sticks that have fallen into the water. It also
spreads over the surface of bricks, and I have found a specimen on a
living shell of the common mollusc _Melania tuberculata_. Dr. Henderson
obtained specimens at Madras from the surface of a freshwater shrimp,
_Palæmon malcolmsonii_. In the ponds at Port Canning the zoaria grow
side by side with, and even entangled with those of _Bowerbankia
caudata_ subsp. _bengalensis_, to the zooecia of which their zooecia
bear a very strong external resemblance so far as their distal extremity
is concerned. This resemblance, however, disappears in the case of
zooecia that bear terminal buds, for no such buds are borne by _B.
caudata_; and the yellowish tint of the zoaria of _V. bengalensis_ is
characteristic. Zoaria of the entoproct _Loxosomatoides colonialis_ and
colonies of the hydroid _Irene ceylonensis_ are also found entangled
with the zoaria of _V. bengalensis_, the zooecia of which are often
covered with various species of Vorticellid protozoa and small rotifers.
The growth of _V. bengalensis_ is more vigorous than that of the other
polyzoa found with it, and patches of _B. caudata_ are frequently
surrounded by large areas of _V. bengalensis_.

The food of _V. bengalensis_ consists largely of diatoms, the siliceous
shells of which often form the greater part of its excreta. Minute
particles of silt are sometimes retained in the gizzard, being
apparently swallowed by accident.

There are still many points to be elucidated as regards the production
and development of the resting buds in _V. bengalensis_, but two facts
are now quite clear as regards them: firstly, that these buds are
produced at the approach of the hot weather and germinate in November or
December; and secondly, that the whole zoarium may be transformed at the
former season into a layer of resting buds closely pressed together but
sometimes exhibiting in their arrangement the typical cruciform
formation. Resting buds may often be found in vigorous colonies as late
as the beginning of December; these buds have not been recently formed
but have persisted since the previous spring and have not yet
germinated. Sometimes only one or two buds are formed at the base of an
existing zooecium (fig. 37 _a_), but apparently it is possible not only
for a zooecium to be transformed into a resting bud but for it to
produce four other buds round its base before undergoing the change.
Young polypides are formed inside the buds and a single zooecium sprouts
out of each, as a rule by the growth of one of the basal projections,
when conditions are favourable.

Polypides of _V. bengalensis_ are often transformed into brown bodies.
When this occurs the orifice closes together, with the collar expanded
outside the zooecium. I have occasionally noticed that the ectocyst of
such zooecia was distinctly thicker and darker in colour than that of
normal zooecia.

Eggs and spermatozoa are produced in great numbers, as a rule
simultaneously in the same zooecia, but individuals kept in captivity
often produce spermatozoa only. The eggs are small and are set free as
eggs. Nothing is known as regards their development.

Polypides are as a rule found in an active condition only in the cold
weather, but I have on one occasion seen them in this condition in
August, in a small zoarium attached to a shell of _Melania tuberculata_
taken in a canal of brackish water near Calcutta.


Family HISLOPIIDÆ.

     HISLOPIDÉES, Jullien, Bull. Soc. zool. France, x, p. 180
     (1885).

     HISLOPIIDÆ, Annandale, Rec. Ind. Mus. i, p. 200 (1907).

_Zoarium_ recumbent, often forming an almost uniform layer on solid
subjects.

_Zooecia_ flattened, adherent; the orifice dorsal, either surrounded by
a chitinous rim or situated at the tip of an erect chitinous tubule; no
parietal muscles.

_Polypide_ with an ample gizzard which possesses a uniform chitinous
lining and does not close together when the polypide is retracted.

_Resting bud_, not produced.

Only two genera can be recognized in this family, _Arachnoidea_, Moore,
from Central Africa, and _Hislopia_, Carter, which is widely distributed
in Eastern Asia. The former genus possesses an upright orificial tubule
and has zooecia separated by basal tubules. Its anatomy is imperfectly
known, but it certainly possesses a gizzard of similar structure to that
of _Hislopia_, between which and _Victorella_ its zooecium is
intermediate in form.


Genus HISLOPIA, _Carter_.

     _Hislopia_, Carter, Ann. Nat. Hist. (3) i, p. 169 (1858).

     _Hislopia_, Stolickza, J. As. Soc. Bengal, xxxviii (2), p.
     61 (1869).

     _Norodonia_, Jullien, Bull. Soc. zool. France, v, p. 77
     (1880).

     _Hislopia_, _id._, _ibid._ x, p. 183 (1885).

     _Norodonia_, _id._, _ibid._ p. 180.

     _Echinella_, Korotneff, Biol. Centrbl. xxi, p. 311 (1901).

     _Hislopia_, Annandale, J. As. Soc. Bengal (new series) ii,
     p. 59 (1906).

     _Hislopia_, Loppens, Ann. Biol. lacustre, iii, p. 175
     (1908).

TYPE, _Hislopia lacustris_, Carter.

_Zoarium._ The zoarium consists primarily of a main axis running in a
straight line, with lateral branches that point forwards and outwards.
Further proliferation, however, often compacts the structure into an
almost uniform flat area.

_Zooecia._ The zooecia (fig. 35 B, p. 190) are flat and have the orifice
surrounded by a chitinous rim but not much raised above the dorsal
surface. They arise directly one from another.

_Polypide._ The polypide possesses from 12 to 20 tentacles. Its
funiculus is rudimentary or absent. Neither the ovaries nor the testes
have any fixed position on the lateral walls of the zooecium to which
they are confined.

The position of this genus has been misunderstood by several zoologists.
Carter originally described _Hislopia_ as a cheilostome allied to
_Flustra_; in 1880 Jullien perpetuated the error in describing his
_Norodonia_, which was founded on dried specimens of Carter's genus;
while Loppens in 1908 still regarded the two "genera" as distinct and
placed them both among the cheilostomes. In 1885, however, Jullien
retracted his statement that _Norodonia_ was a cheilostome and placed
it, together with _Hislopia_, in a family of which he recognized the
latter as the eponymic genus. Carter's mistake arose from the fact that
he had only examined preserved specimens, in which the thickened rim of
the orifice is strongly reminiscent of the "peristome" of certain
cheilostomes, while the posterior of the four folds into which the
tentacle sheath naturally falls (as in all ctenostomes, _cf._ the
diagram on p. 191) is in certain conditions rather larger than the other
three and suggests the "lip" characteristic of the cheilostomes. If
living specimens are examined, however, it is seen at once that the
posterior fold, like the two lateral folds and the anterior one, changes
its form and size from time to time and has no real resemblance to a
"lip."

That there is a remarkable, if superficial, resemblance both as regards
the form of the zooecium and as regards the method of growth between
_Hislopia_ and certain cheilostomes cannot be denied, but the structure
of the orifice and indeed of the whole organism is that of a ctenostome
and the resemblance must be regarded as an instance of convergence
rather than of genetic relationship.

The most striking feature of the polypide of _Hislopia_ is its gizzard
(fig. 38, p. 201) which is perhaps unique (except for that of
_Arachnoidea_) both in structure and function. In structure its
peculiarities reside mainly in three particulars: (i), it is not
constricted off directly from the thin-walled oesophageal tube, but
possesses at its upper extremity a thick-walled tubular portion which
can be entirely closed from the oesophagus at its upper end but always
remains in communication with the spherical part of the gizzard; (ii),
this spherical part of the gizzard is uniformly lined with a thick
chitinous or horny layer which in optical section has the appearance of
a pair of ridges; and (iii), there is a ring of long and very powerful
cilia round the passage from the gizzard to the stomach. The cardiac
limb of the stomach, which is large and heart-shaped, is obsolete. The
wall of the spherical part of the gizzard consists of two layers of
cells, an outer muscular layer consisting of powerful circular muscles
and an inner glandular layer, which secretes the chitinous lining. The
inner walls of the tubular part consist of non-ciliated columnar cells,
and when the polypide is retracted it lies almost at right angles to the
main axis of the zooecium.

The spherical part of the gizzard invariably contains a number of green
cells, which lie free in the liquid it holds and are kept in motion by
the cilia at its lower aperture. The majority of these cells can be seen
with the aid of a high power of the microscope to consist of a hard
spherical coat or cyst containing green protoplasm in which a spherical
mass of denser substance (the nucleus) and a number of minute
transparent granules can sometimes be detected. The external surface of
many of the cysts is covered with similar granules, but some are quite
clean.

There can be no doubt that these cysts represent a stage in the
life-history of some minute unicellular plant or animal. Indeed,
although it has not yet been found possible to work out this
life-history in detail, I have been able to obtain much evidence that
they are the resting stage of a flagellate organism allied to _Euglena_
which is swallowed by the polyzoon and becomes encysted in its gizzard,
extruding in so doing from its external surface a large proportion of
the food-material that it has stored up within itself in the form of
transparent granules. It may also be stated that some of the organisms
die and disintegrate on being received into the gizzard, instead of
encysting themselves.

So long as the gizzard retains its spherical form the green cells and
its other contents are prevented from entering the stomach by the
movements of the cilia that surround its lower aperture, but every now
and then, at irregular intervals, the muscles that form its outer wall
contract. The chitinous lining although resilient and not inflexible is
too stiff to prevent the lumen of the gizzard being obliterated, but the
action of the muscles changes its contents from a spherical to an ovoid
form and in so doing presses a considerable part of them down into the
stomach, through the ring of the cilia.

[Illustration: Fig. 38.--Optical section of gizzard of _Hislopia
lacustris_, with contained green cysts, × 240.]

The contraction of the gizzard is momentary, and on its re-expansion
some of the green cysts that have entered the stomach are often
regurgitated into it. Some, however, remain in the stomach, in which
they are turned round and round by the action of the cilia at both
apertures. They are apparently able to retain their form for some hours
in these circumstances but finally disintegrate and disappear, being
doubtless digested by the juices poured out upon them by the glandular
lining of the stomach. In polypides kept under observation in clean
tap-water all the cysts finally disappear, and the fæces assume a green
colour. In preserved specimens apparently unaltered cysts are sometimes
found in the rectum, but this is exceptional: I have observed nothing of
the kind in living polypides. Cysts often remain for several days
unaltered in the gizzard.

Imperfect as these observations are, they throw considerable light on
the functions of the gizzard in _Hislopia_. Primarily it appears to act
as a food-reservoir in which the green cysts and other minute organisms
can be kept until they are required for digestion. When in the gizzard
certain organisms surrender a large proportion of the food-material
stored up for their own uses, and this food-material doubtless aids in
nourishing the polyzoon. Although the cysts in the gizzard are
frequently accompanied by diatoms, the latter are not invariably
present. The cysts, moreover, are to be found in the zooecia of
polypides that have formed brown bodies, often being actually enclosed
in the substance of the brown body. The gizzards of the specimens of
_Arachnoidea_ I have examined contain cysts that resemble those found in
the same position in _Hislopia_.

_Hislopia_ is widely distributed in the southern part of the Oriental
Region, and, if I am right in regarding _Echinella_, Korotneff as a
synonym, extends its range northwards to Lake Baikal. It appears to be a
highly specialized form but is perhaps related, through _Arachnoidea_,
to _Victorella_.


27. Hislopia lacustris, _Carter_.

     _Hislopia lacustris_, Carter, Ann. Nat. Hist. (3) i, p. 170,
     pl. vii, figs. 1-3 (1858).

     _Norodonia cambodgiensis_, Jullien, Bull. Soc. zool. France,
     v, p. 77, figs. 1-3 (1880).

     _Norodonia sinensis_, _id._, _ibid._ p. 78, figs. 1-3.

     _Norodonia cambodgiensis_, _id._, _ibid._ x, p. 181, figs.
     244, 245 (1885).

     _Norodonia sinensis_, _id._, _ibid._ p. 182, figs. 246, 247.

     _Hislopia lacustris_, Annandale, J. As. Soc. Bengal (new
     series) iii, p. 85 (1907).

     _Hislopia lacustris_, Walton, Rec. Ind. Mus. i, p. 177
     (1907).

     _Hislopia lacustris_, Kirkpatrick, _ibid._ ii, p. 98 (1908).

     _Hislopia lacustris_, Walton, _ibid._ iii, p. 295 (1909).

_Zoarium._ The zoarium forms a flat, more or less solid layer and is
closely adherent to foreign objects. As a rule it covers a considerable
area, with radiating branches at the edges; but when growing on slender
twigs or the stems of water-plants it forms narrow, closely compressed
masses. One zooecium, however, never grows over another.

_Zooecia._ The zooecia are variable in shape. In zoaria which have space
for free expansion they are as a rule irregularly oval, the posterior
extremity being often narrower than the anterior; but small triangular
zooecia and others that are almost square may often be found. When
growing on a support of limited area the zooecia are smaller and as a
rule more elongate. The orifice is situated on a slight eminence nearer
the anterior than the posterior margin of the dorsal surface. It is
surrounded by a strong chitinous rim, which is usually square or
subquadrate but not infrequently circular or subcircular. Sometimes a
prominent spine is borne at each corner of the rim, but these spines are
often vestigial or absent; they are rarely as long as the transverse
diameter of the orifice. The zooecium is usually surrounded by a
chitinous margin, and outside this margin there is often a greater or
less extent of adherent membrane. In some zooecia the margin is obsolete
or obsolescent. The dorsal surface is of a glassy transparency but by no
means soft.

[Illustration: Fig. 39.--_Hislopia lacustris._

A=part of a zoarium of the subspecies _moniliformis_ (type specimen,
from Calcutta), × 15; A=green cysts in gizzard; E=eggs.

B=outline of part of a zoarium of the typical form of the species from
the United Provinces, showing variation in the form of the zooecia and
of the orifice, × 15.]

_Polypide._ The polypide has from 12 to 20 tentacles, 16 being a common
number.

TYPE probably not in existence. It is not in the British Museum and
Prof. Dendy, who has been kind enough to examine the specimens from
Carter's collection now in his possession, tells me that there are none
of _Hislopia_ among them.


27 _a._ Subsp. moniliformis, nov.

     _Hislopia lacustris_, Annandale, J. As. Soc. Bengal (new
     series) ii, p. 59, fig. 1 (1906).

In this race, which is common in Calcutta, the zooecia are almost
circular but truncate or concave anteriorly and posteriorly. They form
linear series with few lateral branches. I have found specimens
occasionally on the shell of _Vivipara bengalensis_, but they are much
more common on the leaves of _Vallisneria spiralis_.

TYPE in the Indian Museum.

The exact status of the forms described by Jullien as _Norodonia
cambodgiensis_ and _N. sinensis_ is doubtful, but I see no reason to
regard them as specifically distinct from _H. lacustris_, Carter, of
which they may be provisionally regarded as varieties. The variety
_cambodgiensis_ is very like my subspecies _moniliformis_ but has the
zooecia constricted posteriorly, while var. _sinensis_, although the
types were found on _Anodonta_ shells on which there was plenty of room
for growth, resemble the confined phase of _H. lacustris_ so far as the
form of their zooecia and of the orifice is concerned.

GEOGRAPHICAL DISTRIBUTION.--The typical form is common in northern India
and occurs also in Lower Burma; the subspecies _moniliformis_ appears to
be confined to Lower Bengal, while the varieties _cambodgiensis_ and
_sinensis_ both occur in China, the former having been found also in
Cambodia and Siam. Indian and Burmese localities are:--BENGAL, Calcutta
(subsp. _moniliformis_); Berhampur, Murshidabad district (_J. Robertson
Milne_): CENTRAL PROVINCES, Nagpur (_Carter_): UNITED PROVINCES,
Bulandshahr (_H. J. Walton_): BURMA, Pegu-Sittang Canal (_Kirkpatrick_).

BIOLOGY.--Regarding the typical form of the species Major Walton writes
(Rec. Ind. Mus. iii, p. 296):--"In volume i (page 177) of the Records of
the Indian Museum, I described the two forms of colonies of _Hislopia_
that I had found in the United Provinces (Bulandshahr). Of these, one
was a more or less linear arrangement of the zooecia on leaves and
twigs, and the other, and more common, form was an encrusting sheath on
the outer surface of the shells of _Paludina_. During the present
'rains' (July 1908) I have found many examples of what may be considered
a much exaggerated extension of the latter form. These colonies have
been on bricks, tiles, and other submerged objects. The largest colony
that I have seen so far was on a tile; one side of the tile was exposed
above the mud of the bottom of the tank, and its area measured about 120
square inches; the entire surface was almost completely covered by a
continuous growth of _Hislopia_. Another large colony was on a piece of
bark which measured 7 inches by 3 inches; both sides were practically
everywhere covered by _Hislopia_."

Major Walton also notes that in the United Provinces the growth of
_Hislopia_ is at its maximum during "rains," and that at that time of
year almost every adult _Paludina_ in a certain tank at Bulandshahr had
its shell covered with the zooecia. The Calcutta race flourishes all the
year round but never forms large or closely compacted zoaria, those on
shells of _Vivipara_ exactly resembling those on leaves of
_Vallisneria_.

In Calcutta both eggs and spermatozoa are produced at all times of the
year simultaneously in the same zooecia, but the eggs in one zooecium
often vary greatly in size. When mature they reach relatively
considerable dimensions and contain a large amount of food material; but
they are set free from the zooecium as eggs. They lie loose in the
zooecium at a comparatively small size and grow in this position.
Nothing is known as regards the development of _Hislopia_.

Both forms of the species appear to be confined to water that is free
from all traces of contamination with brine.


Order PHYLACTOLÆMATA.

The polypide in this order possesses a leaf-like ciliated organ (the
epistome) which arises within the lophophore between the mouth and the
anus and projects upwards and forwards over the mouth, which it can be
used to close. The zooecia are never distinct from one another, but in
dendritic forms such as _Plumatella_ the zoarium is divided at irregular
intervals by chitinous partitions. The lophophore in most genera is
horseshoe-shaped instead of circular, the part opposite the anus being
deeply indented. There are no parietal muscles. The orifice of the
zooecium is always circular, and there is no trace of any structure
corresponding to the collar of the ctenostomes. The tentacles are always
webbed at the base.

All the phylactolæmata produce the peculiar reproductive bodies known as
statoblasts.

The phylactolæmata, which are probably descended from ctenostomatous
ancestors, are confined to fresh or slightly brackish water. Most of the
genera have a wide geographical distribution, but (with the exception of
a few statoblasts of almost recent date) only one fossil form
(_Plumatellites_, Fric. from the chalk of Bohemia) has been referred to
the order, and that with some doubt.

It is convenient to recognize two main divisions of the phylactolæmata,
but these divisions hardly merit the distinction of being regarded as
suborders. They may be called Cristatellina and Plumatellina and
distinguished as follows:--

Division I, PLUMATELLINA, nov.--Ectocyst well developed; zoaria without
a special organ of progression; polypides contained in tubes.

Division II, CRISTATELLINA, nov.--Ectocyst absent except at the base of
the zoarium which is modified to form a creeping "sole"; polypides
embedded in a common synoecium of reticulate structure.

The Cristatellina consist of a single genus and probably of a single
species (_Cristatella mucedo_, Cuvier), which is widely distributed in
Europe and N. America, but has not been found in the Oriental Region.
Eight genera of Plumatellina are known, and five (possibly six) of these
genera occur in India.


Division PLUMATELLINA, nov.

The structure of the species included in this division is very uniform
as regards the internal organs (see fig. 40 opposite and fig. 47 _a_, p.
236). The alimentary canal is simpler than that of the Paludicellidæ. A
short oesophagus leads directly into the stomach, the cardiac portion of
which is produced as a vertical limb almost cylindrical in form and not
constricted at the base. This limb is as a rule of greater length than
the oesophagus. The pyloric part of the stomach is elongated and narrow,
and the intestine short, straight, and of ovoid form. There are no cilia
at the pyloric opening. A single funiculus joins the posterior end of
the stomach to the wall of the zooecium, bearing the statoblasts. Sexual
organs are often absent.

[Illustration: Fig. 40.--Structure of the Plumatellina (after Allman).

A=a zooecium of _Fredericella_ with the polypide extruded. B=the
lophophore of _Lophopus_ (tentacles removed) as seen obliquely from the
right side. C=larva of _Plumatella_ as seen in optical section.
_a_=tentacles; _b_=velum; _c_=epistome; _d_=mouth; _e_=oesophagus;
_f_=stomach; _g_=intestine; _h_=anus; _j_=retractor muscle;
_k_=parieto-vaginal muscles; _l_=funiculus.]

Two families may be recognized as constituting the division, _viz._,
(_a_) the Fredericellidæ, which have a circular or oval lophophore and
simple statoblast without a swim-ring, and (_b_) the Plumatellidæ, in
which the lophophore is shaped like a horseshoe and some or all of the
statoblasts are provided with a ring of air-spaces.


Family 1. FREDERICELLIDÆ.

     FREDERICELLIDÆ, Kraepelin, Deutsch. Süsswasserbryozoen, i,
     p. 168 (1887).

_Zoaria_ dendritic; _zooecia_ distinctly tubular, with the ectocyst well
developed; _statoblasts_ of one kind only, each surrounded by a
chitinous ring devoid of air-spaces; _polypides_ with the lophophore
circular or oval when expanded.

The Fredericellidæ consist of a single genus (_Fredericella_) which
includes several closely-allied forms and has a wide geographical
distribution.


Genus FREDERICELLA, _Gervais_ (1838).

     _Fredericella_, Allman, Mon. Fresh-Water Polyzoa, p. 11
     (1857).

     _Plumatella_, ("arrêt de développement") Jullien, Bull. Soc.
     zool. France, x, p. 121 (1885).

       _Fredericella_, Kraepelin, Deutsch. Süsswasserbryozoen,
     i, p. 99 (1887).

     _Fredericella_, Goddard, Proc. Linn. Soc. N. S. Wales,
     xxxiv, p. 489 (1909).

This genus has the characters of the family. Its status has been much
disputed, some authors regarding the shape of the lophophore as of great
morphological importance, while Jullien believed that _Fredericella_ was
merely an abnormal or monstrous form of _Plumatella_. The latter belief
was doubtless due to the fact that the zoaria of the two genera bear a
very close external resemblance to one another and are sometimes found
entangled together. The importance of the shape of the lophophore may,
however, easily be exaggerated, for, as both Jullien and Goddard have
pointed out, it assumes an emarginate form when retracted.

The best known species is the European and N. American _F. sultana_
(Blumenbach), of which several varieties or phases have been described
as distinct. This form is stated to occur also in S. Africa. _F.
australiensis_, Goddard[BC] from N. S. Wales is said to differ from this
species in having an oval instead of a circular lophophore and in other
small anatomical characters; but it is doubtful how far these characters
are valid, for the lophophore appears to be capable of changing its
shape to some slight extent and has been stated by Jullien to be
habitually oval in specimens from France. _F. cunningtoni_,
Rousselet[BD] from Lake Tanganyika has stout zooecia encrusted with
relatively large sand-grains.

     [Footnote BC: Proc. Linn. Soc. N. S. Wales, xxxiv, p. 489
     (1909).]

     [Footnote BD: Rousselet, Proc. Zool. Soc. London, 1907 (1),
     p. 254.]

The zoaria of _Fredericella_ are usually found attached to solid objects
in shallow water, but a form described as _F. duplessisi_, Ford has been
found at a depth of 40 fathoms embedded in mud at the bottom of the Lake
of Geneva. _F. cunningtoni_ was dredged from depths of about 10 and
about 25 fathoms.

The statoblasts of this genus do not float and often germinate in the
parent zooecium after its polypides have died. They are produced in
smaller numbers than is usually the case in other genera of the order.
The polypides sometimes undergo a process of regeneration, but without
the formation of brown bodies.

[Illustration: Fig. 41.--_Fredericella indica._

A=statoblast, × 120. B=outline of expanded lophophore and adjacent
parts, × 75; a=anus, r=rectum. C=outline of zoarium on leaf of
water-plant, × 3.

(A and B are from specimens from Igatpuri, C from specimen from
Shasthancottah).]


28. Fredericella indica, _Annandale_.

     _Fredericella indica_, Annandale, Rec. Ind. Mus. iii, p. 373,
     fig. (1909).

     _Fredericella indica_, _id._, _ibid._ v, p. 39 (1910).

_Zoarium._ The zoarium is of delicate appearance and branches sparingly.
It is often entirely recumbent but sometimes produces short, lax
branches that consist of two or three zooecia only.

_Zooecia._ The zooecia are very slender and almost cylindrical; they are
slightly emarginate and furrowed, the keel in which the furrow runs
being sometimes prominent. The external surface is minutely roughened
and apparently soft, for small grains of sand and other débris cling to
it, but never thickly. The ectocyst is practically colourless but not
transparent.

_Statoblasts._ The statoblasts are variable in size and form but most
commonly have a regular broad oval outline; sometimes they are
kidney-shaped. The dorsal surface is covered with minute star-shaped
prominences, which sometimes cover it almost uniformly and are sometimes
more numerous in the centre than towards the periphery. The ventral
surface is smooth.

_Polypide._ The lophophore bears about 20-25 tentacles, which are very
slender and of moderate length; the velum at their base is narrow; as a
rule the lophophore is accurately circular.

TYPE in the Indian Museum.

The most definite character in which this species differs from _F.
sultana_ and _F. australiensis_ is the ornamentation of one surface of
the statoblast, both surfaces of which are smooth in the two latter
species. From _F. cunningtoni_, the statoblasts of which are unknown, it
differs in having almost cylindrical instead of depressed zooecia and in
not having the zooecia densely covered with sand-grains.

GEOGRAPHICAL DISTRIBUTION.--Western India (the Malabar Zone): Igatpuri
Lake, W. Ghats (alt. ca. 2,000 feet), Bombay Presidency, and
Shasthancottah Lake near Quilon, Travancore.

BIOLOGY.--In both the lakes in which the species has yet been found it
was collected in November. The specimens obtained in Travancore were
found to be undergoing a process of regeneration due at least partly to
the fact that most of the polypides had perished and that statoblasts
were germinating in the old zooecia. Specimens from the Bombay
Presidency, which were obtained a little later in the month, were in a
more vigorous condition, although even they contained many young
polypides that were not yet fully formed. It seems, therefore, not
improbable that _F. indica_ dies down at the beginning of the hot
weather and is regenerated by the germination of its statoblasts at the
beginning of the cold weather.

At Shasthancottah zoaria were found entangled with zoaria of a delicate
form of _Plumatella fruticosa_ to which they bore a very close external
resemblance.


Family 2. PLUMATELLIDÆ.

     PLUMATELLIDÆ, Allman (_partim_), Mon. Fresh-Water Polyzoa,
     pp. 76, 81 (1857).

Phylactolæmata which have horseshoe-shaped lophophores and a
well-developed ectocyst not specialized to form an organ of progression.
Some or all of the statoblasts are provided with a "swim-ring"
consisting of symmetrically disposed, polygonal chitinous chambers
containing air.

It is convenient to divide the Plumatellidæ as thus defined into
subfamilies (the Plumatellinæ and the Lophopinæ), which may be defined
as follows:--


Subfamily A. PLUMATELLINÆ.

Zoarium dendritic or linear, firmly fixed to extraneous objects; zooecia
tubular, not fused together to form a gelatinous mass.


Subfamily B. LOPHOPINÆ.

Zoarium forming a gelatinous mass in which the tubular nature of the
zooecia almost disappears, capable to a limited extent of progression
along a smooth surface.

Both these subfamilies are represented in the Indian fauna, the
Plumatellinæ by two of the three genera known to exist, and the
Lophopinæ by two (or possibly three) of the four that have been
described. The following key includes all the known genera, but the
names of those that have not been recorded from India are enclosed in
square brackets.


_Key to the Genera of_ Plumatellidæ.

  I.  Statoblasts without marginal processes.
    A. Zooecia cylindrical, not embedded in a gelatinous
       investment (Plumatellinæ).
      _a_.  Zooecia arising directly from one another;
            no stolon; free statoblast oval          PLUMATELLA, p. 212.
      _a'_. Zooecia arising singly or in groups from
            an adherent stolon; free statoblasts oval. STOLELLA, p. 229.
    B. Zooecia cylindrical, embedded in a structureless
       gelatinous investment.
       Zooecia arising from a ramifying stolon;
       statoblasts circular                               [STEPHANELLA.]
    C. Polypides embedded in a hyaline synoecium
       that conceals the cylindrical form of the
       zooecia (Lophopinæ).
      _c_.  Polypides upright, their base far removed
            from that of the zoarium when they are
            expanded                                   LOPHOPUS, p. 231.
      _c'_. Polypides recumbent for the greater
            part of their length at the base of
            the zoarium                               [AUSTRALELLA[BE].]
  II. Statoblasts armed (normally) with hooked
      processes (Lophopinæ).
     A. Processes confined to the extremities of
        the statoblast; zoaria remaining separate
        throughout life                            LOPHOPODELLA, p. 231.
     B. Processes entirely surrounding the
        statoblast; many zoaria embedded in a
        common gelatinous investment so as to
        form large compound colonies               PECTINATELLA, p. 235.

     [Footnote BE: See Rec. Ind. Mus. v, p. 40, footnote (1910).]


Subfamily A. PLUMATELLINÆ.

Of the two Indian genera of this subfamily, one (_Plumatella_) is almost
universally distributed, while the other (_Stolella_) has only been
found in the valley of the Ganges. The third genus of the subfamily
(_Stephanella_) is only known from Japan.

It should be noted that zoaria of different species and genera of this
subfamily are often found in close proximity to one another and to
zoaria of _Fredericella_, and that the branches of the different species
are sometimes entangled together in such a way that they appear, unless
carefully separated, to belong to the same zoarium.


Genus 1. PLUMATELLA, _Lamarck_.

     _Plumatella_, Lamarck, Animaux sans Vert. (ed. 1re) ii, p.
     106 (1816).

     _Alcyonella_, _id_., _ibid_. p. 100.

     _Plumatella_, Allman, Mon. Fresh-Water Polyzoa, p. 92
     (1857).

     _Alcyonella_, _id_., _ibid_. p. 86.

     _Plumatella_, Hyatt, Comm. Essex Inst. iv, p. 207, pl. viii
     (1866).

     _Plumatella_, Jullien (_partim_), Bull. Soc. zool. France,
     x, p. 100 (1885).

     _Hyalinella_, _id_., _ibid_. p. 133.

     _Plumatella_, Kraepelin, Deutsch. Süsswass. Bryozoen, i, p.
     104 (1887).

     _Plumatella_, Braem, Unter. ü. Bryozoen des süssen Wassers,
     p. 2 (Bibliotheca Zoologica, ii, 1890).

_Zoarium_ dendritic, recumbent, erect, or partly recumbent and partly
erect.

_Zooecia_ tubular, not confined in a gelatinous synoecium; the ectocyst
usually horny.

_Statoblasts_ often of two kinds, free and stationary, the latter
without air-cells and as a rule adherent by one surface, the former
provided with a well-developed ring of air-cells but without marginal
processes, oval in form, never more than about 0.6 mm. in length.

_Polypide_ with less than 65 tentacles.

[Illustration: Fig. 42.--Outlines of free statoblasts of _Plumatella_
(enlarged).

A, of _P. fruticosa_ (Calcutta); B, of _P. emarginata_ (Calcutta); C, of
_P. javanica_ (Travancore); D, of _P. diffusa_ (Sikhim); E, of _P.
allmani_ (Bhim Tal); F, of _P. diffusa_ (Rajshahi, Bengal); G, G', of
_P. punctata_ (Calcutta); H, of _P. diffusa_ (Sikhim), statoblast
further enlarged: A=outline of capsule; B=limit of swim-ring on
ventral surface; C=limit of swim-ring on dorsal surface. [The dark
area represents the capsule of the statoblast.]]

Certain forms of this genus are liable to become compacted together in
such a way as to constitute solid masses consisting of elongate vertical
zooecia closely parallel to one another and sometimes agglutinated by
means of a gummy substance. These forms were given by Lamarck in 1816
the name _Alcyonella_, and there has been much dispute as to whether
they represent a distinct genus, distinct species, or merely varieties
or phases of more typical forms. It appears to be the case that all
species which produce vertical branches are liable to have these
branches closely packed together and the individual zooecia of which
they are composed more or less greatly elongated. It is in this way that
the form known to Allman as _Alcyonella benedeni_ is produced from the
typical _Plumatella emarginata_. Other forms go further and secrete a
gummy substance that glues the upright zooecia together and forces them
to elongate themselves without branching. In these conditions the
zooecia become polygonal in cross-section. It is probable that such
forms (_e. g._, _Plumatella fungosa_ (Pallas)) should rank as distinct
species, for the gummy secretion is present in great profusion even in
young zoaria in which the zooecia have not yet assumed a vertical
position. No such form, however, has as yet been found in India, and in
any case it is impossible to regard _Alcyonella_ as a distinct genus.


  _Key to the Indian Species of_ Plumatella.

   I.  Ectocyst more or less stiff, capable of
       transverse wrinkling only near the tips of
       the zooecia, never contractile or greatly
       swollen; zooecia rounded[BF] at the tip when
       the polypide is retracted. Free statoblasts
       elongate; the free portion of their swim-ring
       distinctly narrower at the sides than at
       the ends.
      A. Ectocyst by no means rigid, of a uniform
         pale colour; zooecia never emarginate or
         furrowed, straight, curved or sinuous,
         elongate, cylindrical                      _fruticosa_, p. 217.
      B. Ectocyst rigid; zooecia (or at any rate
         some of the zooecia) emarginate and furrowed.
       _b_.   Ectocyst darkly pigmented over the
              greater part of each zooecium, white
              at the tip; branching of the zoarium
              practically dichotomous, profuse, as
              a rule both horizontal and vertical;
              zooecia straight or slightly curved
              or sinuous                           _emarginata_, p. 220.
       _b'_.  Ectocyst colourless and hyaline;
              branching of the zoarium sparse,
              lateral, irregular, horizontal;
              zooecia nearly straight, strongly
              emarginate and furrowed                _javanica_, p. 221.
       _b''_. The majority of the zooecia distinctly
              L-shaped, one limb being as a rule
              adherent; ectocyst never densely
              pigmented.
          beta.  Zooecia cylindrical, their furrowed
                 keel never prominent                 _diffusa_, p. 223.
          beta'. Zooecia (or at any rate some of the
                 zooecia) constricted or tapering at
                 the base, their emargination and
                 furrow conspicuous                   _allmani_, p. 224.

   II. Ectocyst stiff; zooecia truncated when the
       polypide is retracted. Surface of zooecia
       minutely roughened, distinctly annulate on
       the distal part                             _tanganyikæ_, p. 225.
  III. Ectocyst swollen and contractile, capable
       of transverse wrinkling all over the
       zooecium; zooecia never emarginate            _punctata_, p. 227.

     [Footnote BF: In specimens preserved in spirit they are apt
     to collapse and therefore to become somewhat concave.]

There has always been much difficulty in separating the species of
_Plumatella_, and even now there is no general consensus of opinion as
to the number that should be recognized. The difficulty, however, is
much reduced if the following precautions are observed:--

     (1) If the zoarium appears to be tangled, if the branches
     intertwine or overlap, or if the zooecia are closely pressed
     together, the whole mass should be carefully dissected out.
     This is necessary not only because zoaria belonging to
     different species are sometimes found entangled together but
     also because it is often difficult to recognize the
     characteristic method of branching and shape of the zooecia
     unless it is done.

     (2) As large a part as possible of each zoarium should be
     examined, preferably with a binocular microscope, and
     allowance should be made for irregularities and
     abnormalities of all kinds. What must be observed is the
     rule rather than the exceptions.

     (3) When the statoblasts are being examined, care must be
     taken that they lie flat and that their surface is parallel
     to that of the nose-piece of the microscope. If they are
     viewed obliquely it is impossible to see their true outlines
     and proportions.

     (4) In order to see the relative proportions of the capsule
     and the swim-ring it is necessary that the statoblast should
     be rendered transparent. This is often difficult owing to
     the presence of air in the air-cells, but strong nitric acid
     applied judiciously will render it possible (p. 240).

In supervising the preparation of the plates that illustrate this genus
I have impressed upon the artist the importance of representing what he
saw rather than what he thought he ought to see, and the figures are
very close copies of actual specimens. I have deliberately chosen for
representation specimens of _Plumatella_ preserved by the simple methods
which are often the only ones that it is possible for a traveller to
adopt, for the great majority of naturalists will probably have no
opportunity of examining living specimens or specimens preserved by
special methods, and the main object, I take it, of this series is to
enable naturalists first to distinguish the species described and then
to learn something of their habitat and habits.

GEOGRAPHICAL DISTRIBUTION.--Of the seven species included in this key
five have been found in Europe (namely _P. fruticosa_, _P. emarginata_,
_P. diffusa_, _P. allmani_, and _P. punctata_), while of these five all
but _P. allmani_ are known to occur in N. America also. _P. javanica_ is
apparently peculiar to the Oriental Region, while _P. tanganyikæ_ has
only been taken in Central Africa and in the Bombay Presidency.

TYPES.--Very few of the type-specimens of the older species of
_Plumatella_ are in existence. Allman's are neither in Edinburgh nor in
London, and Mr. E. Leonard Gill, who has been kind enough to go through
the Hancock Collection at Newcastle-on-Tyne, tells me that he cannot
trace Hancock's. Those of the forms described by Kraepelin are in
Hamburg and that of _P. tanganyikæ_ in the British Museum, and there are
schizotypes or paratypes of this species and of _P. javanica_ in
Calcutta. The types of Leidy's species were at one time in the
collection of the Philadelphia Academy of Science.

BIOLOGY.--The zoaria of the species of _Plumatella_ are found firmly
attached to stones, bricks, logs of wood, sticks, floating seeds, the
stems and roots of water-plants, and occasionally to the shells of
molluscs such as _Vivipara_ and _Unio_. Some species shun the light, but
all are apparently confined to shallow water.

Various small oligochæte worms (e. g., _Chætogaster spongillæ_,[BG]
_Nais obtusa_, _Nais elinguis_, _Slavina appendiculata_ and _Pristina
longiseta_[BH]), take shelter amongst them; dipterous larvæ of the genus
_Chironomus_ often build their protective tubes at the base of the
zoaria, and the surface of the zooecia commonly bears a more or less
profuse growth of such protozoa as _Vorticella_ and _Epistylis_. I have
seen a worm of the genus _Chætogaster_ devouring the tentacles of a
polypide that had been accidentally injured, but as a rule the movements
of the lophophore are too quick to permit attacks of the kind, and I
know of no active enemy of the genus. The growth of sponges at the base
of the zoaria probably chokes some species, but one form (_F.
fruticosa_) is able to surmount this difficulty by elongating its
zooecia (p. 219). A small worm (_Aulophorus tonkinensis_) which is
common in ponds in Burma and the east of India as far west as Lucknow,
often builds the tube in which it lives mainly of the free statoblasts
of this genus. It apparently makes no selection in so doing but merely
gathers the commonest and lightest objects it can find, for small seeds
and minute fragments of wood as well as sponge gemmules and statoblasts
of other genera are also collected by it. I know of no better way of
obtaining a general idea as to what sponges and phylactolæmata are
present in a pond than to examine the tubes of _Aulophorus tonkinensis_.

     [Footnote BG: Annandale, J. As. Soc. Bengal (n. s.) ii, p.
     188, pl. i (1906).]

     [Footnote BH: See Michaelsen, Mem. Ind. Mus. i, pp. 131-135
     (1908).]

I am indebted to Mr. F. H. Gravely, Assistant Superintendent in the
Indian Museum, for an interesting note regarding the food of
_Plumatella_. His observations, which were made in Northamptonshire,
were unfortunately interrupted at a critical moment, but I have
reproduced them with his consent in order that other observers may
investigate the phenomena he saw. Mr. Gravely noted that a small green
flagellate which was abundant in water in which _Plumatella repens_ was
growing luxuriantly, was swallowed by the polypides, and that if the
polyparium was kept in a shallow dish of water, living flagellata of the
same species congregated in a little pile under the anus of each
polypide. His preparations show very clearly that the flagellates were
passing through the alimentary canal without apparent change, but the
method of preservation does not permit the retractile granules, which
were present in large numbers in the cell-substance of the flagellates,
to be displayed and it is possible that these granules had disappeared
from those flagellates which are present in the recta of his specimens.
It is clear, therefore, either that certain flagellates must pass
through the alimentary canal of _Plumatella_ unchanged, or that the
polyzoon must have the power of absorbing the stored food material the
flagellates contain without doing them any other injury.

The free statoblasts of _Plumatella_ are as a rule set free before the
cells they contain become differentiated, and float on the surface of
the water for some time before they germinate; but occasionally a small
polypide is formed inside the capsule while it is still in its parent
zooecium. I have, however, seen only one instance of this premature
development, in a single statoblast contained in a small zoarium of _P.
fruticosa_ found in Lower Burma in March. The fixed statoblasts usually
remain fixed to the support of the zoarium, even when their
parent-zooecium decays, and germinate _in situ_.

The larva (fig. 40 C, p. 207) that originates from the egg of
_Plumatella_ is a minute pear-shaped, bladder-like body covered
externally with fine vibratile threads (cilia) and having a pore at the
narrow end. At the period at which it is set free from the parent
zooecium it already contains a fully formed polypide or pair of
polypides with the tentacles directed towards the narrow end. After a
brief period of active life, during which it moves through the water by
means of its cilia, it settles down on its broad end, which becomes
adhesive; the polypide or pair of polypides is everted through the pore
at the narrow end, the whole of this end is turned inside out, and a
fresh polyparium is rapidly formed by budding.


29. Plumatella fruticosa, _Allman_. (Plate III, fig. 1; plate IV, fig.
4; plate V, fig. 1.)

     _Plumatella fruticosa_, Allman, Ann. Nat. Hist. xiii, p. 331
     (1844).

     _Plumatella repens_, van Beneden (? _nec_ Linné), Mém. Acad.
     Roy. Belg. 1847, p. 21, pl. i, figs. 1-4.

     _Plumatella fruticosa_, Johnston, Brit. Zooph. (ed. 2), p.
     404 (1847).

     _Plumatella coralloides_, Allman, Rep. Brit. Assoc. 1850, p.
     335.

     _Plumatella stricta_, _id._, Mon. Fresh-Water Polyzoa, p.
     99, fig. 14 (1857).

     _Plumatella fruticosa_, _id._, _ibid._ p. 102, pl. vi, figs.
     3-5.

     _Plumatella coralloides_, _id._, _ibid._ p. 103, pl. vii,
     figs. 1-4.

     _Plumatella repens_ and _P. stricta_, Carter, Ann. Nat.
     Hist. (3) iii, p. 341 (1859).

     _Plumatella lucifuga_, Jullien (_partim_), Bull. Soc. zool.
     France, x, p. 114 (1885).

     _Plumatella princeps_ var. _fruticosa_, Kraepelin, Deutsch.
     Süsswasserbryozoen, i, p. 120, pl. vii, fig. 148 (1887).

     _Plumatella fruticosa_, Braem, Unter. ii. Bryozoen des
     süssen Wassers, p. 9, pl. i, fig. 15 (Bibl. Zool. ii)
     (1890).

     _Plumatella repens_, Annandale, J. As. Soc. Bengal (new
     series) iii, 1907, p. 88.

     _Plumatella emarginata_, Loppens (_partim_), Ann. Biol.
     lacustre, iii, p. 161 (1908).

     _Plumatella fruticosa_, Annandale, Rec. Ind. Mus. v, p. 45
     (1910).

_Zoarium._ The zoarium in the typical form has a loose appearance due to
the fact that the branches are far apart and the ectocyst by no means
rigid. When young the zoarium is adherent, but in well-grown polyparia
vertical branches, often an inch or more in length, are freely produced.
As a rule they have not the strength to stand upright if removed from
the water. Branching is ordinarily lateral and as a rule occurs chiefly
on one side of a main branch or trunk. In certain circumstances upright
zooecia are pressed together and reach a great length without branching,
and in this form (_P. coralloides_, Allman) daughter-zooecia are often
produced at the tip of an elongated mother-zooecium in fan-like
formation. A depauperated form (_P. stricta_, Allman), occurs in which
the vertical branches are absent or very short. In all forms internal
partitions are numerous and stout.

_Zooecia._ The zooecia are cylindrical and bear a simple keel on their
dorsal surface. They are never emarginate or furrowed. In the typical
form their diameter is more than half a millimetre, and they are always
of considerable length. The ectocyst is thin and never very rigid or
deeply pigmented, the colour usually being an almost uniform pale
pinkish brown and fading little towards the tip of the zooecium.

_Statoblasts._ Both free and stationary statoblasts are formed, but the
latter are rare and do not always adhere. They resemble the free
statoblasts in general form but have a solid margin instead of a
swim-ring and are often minutely serrated round the edge. The free
statoblasts are at least considerably, sometimes very elongate; in all
zoaria it is possible to find specimens that are more than twice as long
as broad. The capsule is relatively large and resembles the swim-ring in
outline, so that the free portion of the latter is not much narrower at
the sides than at the ends. The sides are distinctly convex and the ends
rounded; the swim-ring encroaches little on the surface of the capsule.

_Polypide._ The tentacles number between 40 and 50 and are not festooned
at the base. The stomach is slender and elongate.

TYPE not in existence.

SYSTEMATIC REMARKS.--_P. fruticosa_ is closely allied to _P. repens_
(European and N. American) but always has much longer statoblasts. Three
phases of the species may be distinguished as follows:--

     A. (_Forma typica_). Zooecia stout in form, not greatly
     elongate; free branches produced in profusion.

     B. (_P. stricta_, Allman, _P. repens_, van Beneden). Zooecia
     slender; free branches absent or consisting of two or three
     zooecia only.

     C. (_P. coralloides_, Allman). Vertical zooecia pressed
     together and greatly elongated.

Indian specimens of the typical form agree well with German specimens
labelled by Prof. Kraepelin _P. princeps_ var. _fruticosa_, and
specimens of the _coralloides_ phase could hardly be distinguished from
similar specimens from Scotland.

GEOGRAPHICAL DISTRIBUTION.--_P. fruticosa_ is widely distributed in
Europe and probably in N. America. I have seen Indian specimens from the
Punjab (Lahore, _Stephenson_), from Bombay, from Travancore, from
Calcutta and other places in the Ganges delta, from Rajshahi (Rampur
Bhoolia) on the R. Ganges, from Kurseong in the E. Himalayas (alt. 4,500
feet), and from Kawkareik in Tenasserim. Statoblasts found on the
surface of a pond near Simla in the W. Himalayas (alt. _ca._ 8,000
feet), probably belong to this species.

BIOLOGY.--Allman states that in England _P. fruticosa_ is fond of still
and slowly-running water. The typical form and the _coralloides_ phase
grow abundantly in the Calcutta tanks, the former often attaining an
extraordinary luxuriance. I have found the var. _stricta_ only in water
in which there was reason to suspect a lack of minute life (and
therefore of food), viz. in Shasthancottah Lake in Travancore, in a
swamp in Lower Burma, and in a small jungle stream near the base of the
Western Ghats in Travancore. The species is the only one that I have
seen in running water in India, and the specimens obtained in the jungle
stream in Travancore are the only specimens I have taken in these
circumstances. _P. fruticosa_ always grows near the surface or near the
edge of water; it is found attached to the stems of bulrushes and other
aquatic plants, to floating seeds and logs and (rarely) to stones and
bricks. So far as my experience goes it is only found, at any rate in
Calcutta, in the cold weather and does not make its appearance earlier
than October.

The form Allman called _P. coralloides_ was found by him, "attached to
floating logs of wood, together with _P. repens_ and _Cordylophora
lacustris_, and generally immersed in masses of _Spongilla
fluviatilis_." I have always found it immersed in sponges (_S.
lacustris_, _S. alba_, _S. carteri_, and _S. crassissima_), except when
the sponge in which it had been immersed had decayed. Indeed, the
peculiar form it has assumed appears to be directly due to the pressure
of the growing sponge exerted on the zooecia, for it is often possible
to find a zoarium that has been partially overgrown by a sponge and has
retained its typical form so long as it was free but has assumed the
_coralloides_ form where immersed.[BI] In Shasthancottah Lake,
Travancore, I found specimens of the _stricta_ phase embedded in the
gelatinous mass formed by a social rotifer and to some extent
assimilated to the _coralloides_ form.

     [Footnote BI: Braem (_op. cit._, p. 3, pl. i, fig. 1), has
     described and figured under the name _P. fungosa_ var.
     _coralloides_, Allman, a dense form that somewhat resembles
     this phase of _P. fruticosa_ but has become compacted
     without external pressure. It is, however, probably a form
     of _P. repens_ rather than _P. fungosa_ and differs in its
     broad statoblasts from any form of _P. fruticosa_. I have
     examined specimens of the same form from England.]


30. Plumatella emarginata, _Allman_. (Plate III, fig. 2; plate IV, figs.
1, 1 _a._)

     _Plumatella emarginata_, Allman, Ann. Nat. Hist. xiii, p.
     330 (1844).

     _Plumatella emarginata_, Johnston, Brit. Zooph. (ed. 2), p.
     404 (1847).

     _Alcyonella benedeni_, Allman, Mon. Fresh-Water Polyzoa, p.
     89, pl. iv, figs. 5-11 (1857).

     _Plumatella emarginata_, _id._, _ibid._ p. 104, pl. vii,
     figs. 5-10.

     _Plumatella lucifuga_, Jullien, Bull. Soc. zool. France, x,
     figs. 89, 90, p. 114 (1885).

     _Plumatella princeps_ var. _emarginata_, Kraepelin
     (_partim_), Deutsch. Süsswasserbryoz. p. 120, pl. iv, fig.
     108, pl. v, fig. 123 (1887).

     _Plumatella emarginata_, Braem, Unter. ii. Bryoz. süssen
     Wassers, p. 9, pl. i, figs. 12, 14 (Bibl. Zool. ii) (1890).

     _Plumatella emarginata_, Annandale (_partim_), J. As. Soc.
     Bengal, (new series) iii, 1907, p. 89.

     _Plumatella princeps_, Loppens (_partim_), Ann. Biol.
     lacustre, iii, p. 162, fig. 7 (1908).

     _Plumatella emarginata_, Annandale, Rec. Ind. Mus. v, p. 47
     (1910).

_Zoarium._ The zoarium often covers a considerable area on flat surfaces
and is sometimes entirely recumbent. More usually, however, the younger
part is vertical. In either case the branching is practically
dichotomous, two young zooecia arising almost simultaneously at the tip
of a mother-zooecium and diverging from one another at a small angle.
When the zoarium becomes vertical, rigid branches of as much as an inch
in length are sometimes produced in this way and, arising parallel to
one another, are pressed together to form an almost solid mass
(=_Alcyonella benedeni_, Allman). In such cases the basal zooecium or at
any rate the basal part of each upright branch is considerably
elongated. In recumbent zooecia the main branches often radiate outwards
from a common centre.

_Zooecia._ The zooecia are of almost equal width throughout, slender,
and moderately elongate when recumbent. Their ectocyst is stiff; they
are emarginate at the tip and more or less distinctly furrowed on the
dorsal surface, the keel in which the furrow runs not being prominent.
The orifice is often on the dorsal surface even in upright branches.
Each zooecium is of a dark brown or almost black colour for the greater
part of its length but has a conspicuous white tip which is extended
down the dorsal surface in the form of a triangle, its limits being
rather more extensive than and parallel to those of the emargination.

_Statoblast._ The majority of the free statoblasts are elongate and
truncate or subtruncate at the extremities, the sides being as a rule
straight and parallel. In every polyparium specimens will be found that
are between twice and thrice as long as broad. The capsule is, however,
relatively much broader than the swim-ring, often being nearly circular,
and there is therefore at either end a considerable extent of free
air-cells, while the extent of these cells at the sides of the capsule
is small. The air-cells cover a considerable part of the dorsal surface
of the capsule. Fixed statoblasts are usually found in old colonies,
especially at the approach of the hot weather. They have an oval form
and are surrounded by a membranous margin on which traces of
reticulation can often be detected. As a rule statoblasts of both types
are produced in considerable but not in excessive numbers.

_Polypide._ There are about 40 tentacles, the velum at the base of which
extends upwards for a considerable distance without being festooned. The
stomach is elongate and slender and narrowly rounded at the base.

The method of branching, the coloration of the zooecia and the form of
the free statoblast are all characteristic. Luxuriant or closely
compressed zoaria of _P. diffusa_ often bear a superficial resemblance
to those of _P. emarginata_, but the resemblance disappears if they are
carefully dissected out. Indian specimens of _P. emarginata_ agree
closely with European ones.

GEOGRAPHICAL DISTRIBUTION.--_P. emarginata_ is a common species in
Europe, N. America, and southern Asia and probably also occurs in Africa
and Australia. I have examined specimens from Calcutta, Rangoon, and
Mandalay in Indian territory, and also from Jalor in the Patani States
(Malay Peninsula) and the Talé Noi, Lakon Sitamarat, Lower Siam.
Gemmules found by Apstein (Zool. Jahrb. (Syst.) xxv, 1907, p. 201) in
plankton from the Colombo lake may belong to this species or to any of
the others included by Kraepelin in his _P. princeps_.

BIOLOGY.--In Ireland Allan found _P. emarginata_ in streams and
rivulets, but it also occurs in European lakes. In India I have only
found it in ponds. It prefers to adhere to the surface of stones or
bricks, but when these are not available is found on the stems of
water-plants. In the latter position the form called _Alcyonella
benedeni_ by Allman is usually produced, owing to the fact that the
upright branches are crowded together through lack of space, very much
in the same way (although owing to a different cause) as those of _P.
fruticosa_ are crowded together in the _coralloides_ phase, to which the
_benedeni_ phase of _P. emarginata_ is in many respects analogous.

Although it is essentially a cold-weather species in Calcutta, _P.
emarginata_ is sometimes found in a living condition during the "rains."
Zoaria examined at this season, however, contains few living polypides,
the majority of the zooecia having rotted away and left fixed
statoblasts only to mark their former position.


31. Plumatella javanica, _Kraepelin_.

     _Plumatella javanica_, Kraepelin, Mitt. Nat. Mus. Hamb.
     xxiii, p. 143, figs. 1-3 (1903).

     _Plumatella emarginata_ var. _javanica_, Loppens, Ann. Biol.
     lacustre, iii, p. 162 (1908).

     _Plumatella javanica_, Annandale, Rec. Ind. Mus. v, p. 50
     (1910).

     _Plumatella allmani_ var. _dumortieri_, _id._ (_partim_)
     (_nec_ Allman), _ibid._ p. 49.

This species is related to _P. emarginata_, from which it may be
distinguished by the following characters:--

_Zoarium._ The zoarium is always entirely recumbent and branches
sparingly; its method of branching does not approach the dichotomous
type but is lateral and irregular. Linear series of zooecia without
lateral branches are often formed.

_Zooecia._ The zooecia are slender and often very long; they are
strongly emarginate and furrowed, and the keel that contains the furrow
is conspicuous. The ectocyst is hyaline and as a rule absolutely
colourless.

_Statoblasts._ The free statoblasts are variable in length, sometimes
distinctly elongate, sometimes elongate only to a moderate degree; they
are rounded at the extremities and have the sides slightly or distinctly
convex outwards. The capsule is relatively large, and the free portion
of the swim-ring is not much broader at the ends than at the sides. The
fixed statoblasts are elongate and surrounded by an irregularly shaped
chitinous membrane, which is often of considerable extent. The whole of
the dorsal surface is covered with what appear to be rudimentary
air-spaces some of which even contain air.

The transparent glassy ectocyst and strong furrowed keel of this species
are very characteristic, but the former character is apt to be obscured
by staining due to external causes, especially when the zoarium is
attached to dead wood. The shape of the free statoblasts is too variable
to be regarded as a good diagnostic character, but the fixed
statoblasts, when they are to be found, are very characteristic in
appearance. _P. javanica_ appears to be closely related to Allman's _P.
dumortieri_, with which stained zoaria are apt to be confused. The
character of the ectocyst is, however, different, and the free part of
the swim-ring is distinctly narrower at the sides of the free
statoblasts. Dr. Kraepelin has been kind enough to send me one of the
types.

TYPES in the Hamburg and Indian Museums.

GEOGRAPHICAL DISTRIBUTION.--Java, Penang, India. Indian localities
are:--BENGAL, Calcutta; Berhampore, Murshidabad; R. Jharai, Siripur,
Saran district, Tirhut: E. HIMALAYAS, Kurseong, Darjiling district (alt.
4,500 feet): MADRAS PRESIDENCY, canal near Srayikaad, Travancore. Mr. C.
W. Beebe has recently sent me a specimen taken by him in the Botanical
Gardens at Penang.

BIOLOGY.--Very little is known about the biology of this species.
Kraepelin took it in Java on the leaves of water-lilies. It is not
uncommon during the cold weather in the Calcutta Zoological Gardens on
floating seeds and sticks and on the stems of bulrushes; in Travancore I
took it in November on the submerged leaves of _Pandani_ growing at the
edge of a canal of slightly brackish water. Mr. Hodgart, the collector
of the Indian Museum, found it in the R. Jharai on the stems of
water-plants at a time of flood in the "rains." In Calcutta it is often
found entangled with _P. fruticosa_ and _P. emarginata_.


32. Plumatella diffusa, _Leidy_. (Plate IV, fig. 2.)

     _Plumatella diffusa_, Leidy, P. Ac. Philad. v, p. 261
     (1852).

     _Plumatella diffusa_, Allman, Mon. Fresh-Water Polyzoa, p.
     105 (1857).

     _Plumatella diffusa_, Hyatt, Comm. Essex Inst. iv, pl. viii,
     figs. 11, 12 (1866).

     _Plumatella diffusa_, _id._, _ibid._ v, p. 107, fig. 12
     (1868).

     _Plumatella repens_, Jullien, Bull. Soc. zool. France, x,
     fig. 37 (_lapsus_ for 73), p. 110 (1885).

     _Plumatella diffusa_, _id._, _ibid._ figs. 155, 157, pp.
     130, 131.

     _Plumatella allmani_ var. _diffusa_, Annandale, Rec. Ind.
     Mus. v, p. 49 (1910).

_Zoarium._ The zoarium often covers a considerable area on flat surfaces
and is sometimes found crowded together on the stems of plants. In the
latter case the arrangement of the main branches is distinctly radiate.
Upright branches occur rarely and never consist of more than three
zooecia. The characteristic method of branching is best represented by
the following diagram:--

[Illustration: Fig. 43.]

The partitions are stout and numerous.

_Zooecia._ The great majority of the zooecia in each zoarium are
distinctly L-shaped, the long limb being usually adherent. The vital
organs of the polypide are contained in the vertical limb, while the
horizontal one, in mature polyparia, is packed full of free statoblasts.
The zooecia are cylindrical and as a rule obscurely emarginate and
furrowed. The ectocyst is stiff; it is never deeply pigmented but is
usually of a transparent horn-colour at the base of each zooecium and
colourless at the tip, the contrast between the two portions never being
very strong. The basal portion is rough on the surface, the distal
portion smooth.

_Statoblasts._ Free statoblasts are produced in very great profusion and
fixed statoblasts are also to be found as a rule. The latter resemble
those of _P. emarginata_. The free statoblasts are never very large or
relatively broad, but they vary considerably as regards size and
outline. The capsule is large, the sides convex outwards and the
extremity more or less broadly rounded. The air-cells are unusually
large and extend over a great part of the dorsal surface of the
statoblast.

_Polypide._ The polypide is shorter and stouter than that of _P.
emarginata_ and as a rule has fewer tentacles.

The most characteristic feature of this species is the form of the
zooecia, which differ greatly from those of any other Indian species but
_P. allmani_. In the latter they are distinctly "keg-shaped" (_i. e._,
constricted at the base and swollen in the middle), and the zoarium
never spreads out over large surfaces in the way in which that of _P.
diffusa_ does.

TYPE--? in the Philadelphia Academy of Sciences.

GEOGRAPHICAL DISTRIBUTION.--This species was originally described from
North America (in which it is apparently common) and occurs also in
Europe. I have seen Indian specimens from the following
localities:--BENGAL, Calcutta and neighbourhood; Rajshahi (Rampur
Bhulia): E. HIMALAYAS, Gangtok, Native Sikhim (alt. 6,150 feet)
(_Kirkpatrick_, _Stewart_): PUNJAB, Lahore (_Stephenson_).

BIOLOGY.--_P. diffusa_ in Lower Bengal is a cold-weather species. It is
remarkable for the enormous number of gemmules it produces and is
usually found either on floating objects such as the stems of certain
water-plants, or on stones or bricks at the edge of ponds.


33. Plumatella allmani, _Hancock_. (Plate IV, figs. 3, 3 _a_.)

     _Plumatella allmani_, Hancock, Ann. Nat. Hist. (2) v, p.
     200, pl. v, fig. 3-4, pl. iii, fig. 2-3 (1850).

     _Plumatella allmani_, Allman, Mon. Fresh-Water Polyzoa, p.
     106, fig. 16 (1857).

     _Plumatella elegans_, _id._, _ibid._ p. 107, pl. viii, figs.
     6-10.

     _Plumatella lucifuga_ ("forme rampante") Jullien, Bull. Soc.
     zool. France, x, p. 114 (1885).

This species is closely allied to _P. diffusa_, from which it differs in
the following characters:--

     (1) The zoarium never covers a large area and as a rule
     grows sparingly and mainly in two directions.

     (2) The zooecia are more irregular in shape, not so
     distinctly elbowed, smaller; they have a much more
     prominently keeled ridge. The great majority of them are
     constricted at the base and taper towards the orifice. In
     young zoaria they are almost colourless but in older ones
     there is a band of not very dense pigment round the base of
     the vertical limb.

     (3) The free statoblasts are comparatively large and usually
     show a tendency to taper at the extremities, often being
     almost rhomboidal in form. The swim-ring does not extend so
     far over the dorsal surface as it does in those of _P.
     diffusa_; the "cells" of which it is composed are small.

TYPE not in existence.

I have seen every gradation between this form and Allman's _P. elegans_.

GEOGRAPHICAL DISTRIBUTION.--_P. allmani_ is apparently a rare species to
which there are few references in literature. It was originally
described from England and is stated by Jullien to occur in France. I
have found specimens only in the lake Bhim Tal (alt. 4,500 feet) in the
W. Himalayas.

BIOLOGY.--The original specimens were found by Hancock on stones. My own
were growing on the leaves of water-plants, usually on the under side.
When the zooecia were forced to stretch across from one leaflet to
another they assumed the sinuous form characteristic of Allman's _P.
elegans_.


34. Plumatella tanganyikæ, _Rousselet_.

     _Plumatella tanganyikæ_, Rousselet, Proc. Zool. Soc. London,
     1907 (i), p. 252, pl. xiv, figs. 1-4.

     _Plumatella bombayensis_, Annandale, Rec. Ind. Mus. ii, p.
     169, figs. 1, 2 (1908).

     _Plumatella bombayensis_, _id._, _ibid._ v, p. 51 (1910).

_Zoarium._ The whole colony is recumbent but branches freely and at
short intervals in a horizontal plane, so that the zooecia become
crowded together and the branches sometimes overlap one another. The
zoarium often covers a considerable area, but growth seems to be mainly
in two directions. When growing on the stems of water-plants the
branches are often parallel and closely pressed together but remain
recumbent in this position. A stout membrane sometimes extends between
branches and individual zooecia.

_Zooecia._ The walls of the zooecia are thick, stiff, and more or less
darkly but not opaquely pigmented; the external surface, although not
very smooth, is always clean. The two most noteworthy characters of the
zooecia are (i) their truncated appearance when the polypide is
retracted, and (ii) the conspicuous, although often irregular external
annulation of their walls. The tip of each zooecium, owing to the fact
that the invaginated part of the ectocyst is soft and sharply separated
from the stiffened wall of the tube, terminates abruptly and is not
rounded off gradually as is the case in most species of the genus;
sometimes it expands into a trumpet-like mouth. The annulation of the
external surface is due to numerous thickened areas of the ectocyst
which take the form of slender rings surrounding the zooecium; they are
most conspicuous on its distal half. On the dorsal surface of the base
of each zooecium there is a conspicuous furrowed keel, which, however,
does not usually extend to the distal end; the latter is oval in
cross-section. The zooecia are short and broad; their base is always
recumbent, and, when the zoarium is attached to a stone or shell, often
seems to be actually embedded in the support; the distal part turns
upwards and is free, so that the aperture is terminal; the zooecia of
the older parts of the zoarium exhibit the specific characters much more
clearly than those at the growing points.

_Polypide._ The lophophore bears 20 to 30 tentacles, which are long and
slender; the velum at their base extends up each tentacle in the form of
a sharply pointed projection, but these projections do not extend for
more than one-fifth of the length of the tentacles. Both the velum and
the tentacular sheath bear numerous minute tubercles on the external
surface. The base of the stomach is rounded, and the whole of the
alimentary canal has a stout appearance.

[Illustration: Fig. 44.--_Plumatella tanganyikæ_ from Igatpuri Lake.

A=outline of part of zoarium from a stone, × 16; B=outline of the tip of
a single zooecium, × 70; C=free statoblast, × 70.]

_Statoblasts._ Both fixed and free statoblasts are produced, but not in
very large numbers. The latter are broadly oval and are surrounded by a
stout chitinous ring, which often possesses irregular membranous
projections; the surface is smooth. The free statoblasts are small and
moderately elongate, the maximum breadth as a rule measuring about 2/3
of the length; the capsule is relatively large and the ring of air-cells
is not very much broader at the ends than at the sides; the dorsal
surface of the central capsule is profusely tuberculate. The outline of
the whole structure is often somewhat irregular.

In deference to Mr. Rousselet's opinion expressed in a letter I have
hitherto regarded the Bombay form of this species as distinct from the
African one, and there certainly is a great difference in the appearance
of specimens taken on the lower surface of stones in Igatpuri Lake and
of the types of _P. tanganyikæ_, one of which is now in the collection
of the Indian Museum. The dark colour of the former, however, and their
vigorous growth appear to be directly due to environment, for these
characters disappear to a large extent in specimens growing on the stems
of water-plants in the same lake. Indeed, such specimens are exactly
intermediate between the form "_bombayensis_" and the typical form of
the species. _P. tanganyikæ_ is closely allied to _P. philippinensis_,
Kraepelin, from the island of Luzon, but the latter has a smooth and
polished ectocyst devoid of annulations, and zooecia of a more elongate
and regular form.

TYPES of the species in the British and Indian Museums, those of _P.
bombayensis_ in the latter collection.

GEOGRAPHICAL DISTRIBUTION.--_P. tanganyikæ_ is only known as yet from L.
Tanganyika in Central Africa and from Igatpuri in the Bombay Presidency.

BIOLOGY.--In both localities the zoaria were found in shallow water. In
L. Tanganyika they were encrusting stones and shells, while at Igatpuri
they were fixed for the most part to the lower surface of stones but
were also found on the stems of water-plants. My specimens from the
Bombay Presidency were taken, on two separate occasions, at the end of
November. At that date the zoaria were already decaying and large
blanks, marked out by fixed statoblasts, were often observed on the
stones. Probably, therefore, the species flourishes during the "rains."


35. Plumatella punctata, _Hancock_. (Plate IV, fig. 5.)

    _Plumatella punctata_, Hancock, Ann. Nat. Hist. (2) v, p. 200, pl. iii,
    fig. 1, and pl. v, figs. 6, 7 (1850).

    _Plumatella vesicularis_, Leidy, P. Ac. Philad. vii, p. 192 (1854).

    _Plumatella vitrea_, Hyatt, Comm. Essex Inst. iv, pl. ix, figs. 1, 2
    (1866).

    _Plumatella punctata_, Allman, Mon. Fresh-Water Polyzoa, p. 100,
    fig. 15 (1857).

    _Plumatella vesicularis_, _id._, _ibid._ p. 101.

     _Plumatella vitrea_, Hyatt, Proc. Essex Inst. v, p. 225,
     figs. 18, 19 (1868).

     _Plumatella vesicularis_, _id._, _ibid._ p. 225.

     _Hyalinella vesicularis_, Jullien, Bull. Soc. zool. France,
     x, p. 133, figs. 165-172 (1885).

     _Hyalinella vitrea_, _id._, _ibid._ p. 134, figs. 173-179.

     _Plumatella punctata_, Kraepelin, Deutsch.
     Süsswasserbryozoen, i, p. 126, pl. iv, figs. 115, 116; pl.
     v, figs. 124, 125; pl. vii, figs. 153, 154 (1887).

     _Plumatella vesicularis_, Braem, Unters. ü. Bryozoen süssen
     Wassers, p. 8, pl. i, fig. 8 (Bibl. Zool. ii) (1890).

     _Hyalinella punctata_, Loppens, Ann. Biol. lacustre, iii, p.
     163 (1908).

     _Plumatella punctata_, Annandale, Rec. Ind. Mus. v, p. 52
     (1910).

_Zoarium._ The zoarium is entirely recumbent and often appears to form
an almost uniform flat layer instead of a dendritic body. Sometimes,
however, it is distinctly linear, with lateral branches produced
irregularly at considerable distances apart.

_Zooecia._ The zooecia differ from those of all other species in having
a greatly swollen, soft ectocyst which can be transversely wrinkled all
over the zooecium by the action of the muscles of the polypide and is
distinctly contractile. It is mainly owing to the swollen and almost
gelatinous nature of the ectocyst that the dendritic character of the
zoarium is frequently concealed, for the method of branching is
essentially the same as that of _P. diffusa_, although the zooecia are
not so distinctly elbowed. The ectocyst is colourless or faintly tinted
with brown; as a rule it is not quite hyaline and the external surface
is minutely roughened or tuberculate. The zooecia are not emarginate or
furrowed.

_Statoblasts._ Stationary statoblasts are not found.  The free
statoblasts are variable and often asymmetrical in outline, but the free
portion of the swim-ring is always of nearly equal diameter all round
the periphery and the capsule relatively large. Some of the statoblasts
are always broad in comparison with their length.

_Polypide._ The polypide is comparatively short and stout. European
specimens are said to have from 30 to 40 tentacles, but Indian specimens
have only from 20 to 30.

Shrunken specimens of the less congested forms of this species closely
resemble specimens of _P. repens_, but the statoblasts are more variable
in shape and the ectocyst, even in such specimens, is thicker. Living or
well-preserved specimens cannot be mistaken for those of any other
species. Jullien regarded _P. punctata_ as the type of a distinct genus
(_Hyalinella_) but included in _Plumatella_ at least one form (P.
"_arethusa_") which probably belongs to this species. Kraepelin
distinguishes as "varieties" two phases, a summer phase ("var.
_prostrata_") and an autumn phase ("var. _densa_"). The former often
forms linear series of considerable length with only an occasional
side-branch, while in the autumn phase branching is so profuse and the
branches are so closely pressed together that the zoarium comes to
resemble a uniform gelatinous patch rather than a dendritic growth. A
phase resembling the European autumn form is the commonest in Calcutta
and I have also found one intermediate between this and Kraepelin's
"var. _prostrata_," neither having any seasonal significance in India.

GEOGRAPHICAL DISTRIBUTION.--_P. punctata_ is widely distributed in
Europe and N. America, but in the Oriental Region it has only been found
in Calcutta and the neighbourhood.

BIOLOGY.--In this part of India _P. punctata_ flourishes both during the
"rains" and in winter. I have found specimens in June and July and also
in December and January. The majority of them were attached to bricks,
but some were on the roots of duckweed, the stems of water-plants, and
the tips of creepers falling into water. The species is often found
together with _Stolella indica_ and also with other species of its own
genus. It is most common, in the neighbourhood of Calcutta, in that part
of the town which is near the Salt Lakes, and occurs in ponds the water
of which is slightly brackish.


Genus 2. STOLELLA, _Annandale_.

    _Stolella_, Annandale, Rec. Ind. Mus. iii, p. 279 (1909).

    _Stolella_, _id._, _ibid._ v, p. 53 (1910).

TYPE, _Stolella indica_, Annandale.

_Zoarium_. The zoarium consists of groups of zooecia (or occasionally of
single zooecia) joined together by an adherent rhizome. There is no
gelatinous investment.

_Zooecia._ The adult zooecia resemble those of _Plumatella_ except in
being sometimes more or less upright.

_Polypide_ and _Statoblasts._ The polypide and statoblasts resemble
those of _Plumatella_. Fixed as well as free statoblasts occur.

This genus is closely allied to _Plumatella_, from which it is probably
derived. The root-like tube from which the zooecia arise is formed by
the great elongation of the basal part of a zooecium, and the zoaria
closely resemble those of _P. punctata_, for it is not until several
zooecia have been produced that the characteristic mode of growth
becomes apparent.

_Stolella_ has only been found in India and is monotypic[BJ].

     [Footnote BJ: But see p. 246 (addenda).]


36. Stolella indica, _Annandale_. (Plate V, figs. 3, 4.)

    _Stolella indica_, Annandale, Rec. Ind. Mus. iii, p. 279, fig. (1909).

    _Stolella indica_, _id._, _ibid._ v, p. 53 (1910).

_Zoarium._ The zoarium is adherent and linear, having neither lateral
nor vertical branches.

_Zooecia._ The zooecia are short and slender, erect or nearly so,
distinctly emarginate and furrowed. Their ectocyst is soft, colourless
and transparent but minutely roughened on the surface.

_Polypide._ The tentacles number from 30 to 35 and are rather short and
stout, sometimes being slightly expanded at the tips. The stomach is
comparatively short and abruptly truncated posteriorly.

_Statoblasts._ Both free and fixed statoblasts are found, and both are
variable in form, the latter varying in outline from the circular to the
broadly oval. The free statoblasts resemble those of _Plumatella
punctata_, but are sometimes rather more elongate.

TYPE in the Indian Museum.

[Illustration: Fig. 45.--Zoarium of _Stolella indica_ on stem of
water-plant (from Calcutta), × 6.]

GEOGRAPHICAL DISTRIBUTION.--So far as we know, this species is confined
to the Indo-Gangetic Plain. Major Walton found it at Bulandshahr in the
United Provinces, and it is not uncommon in the neighbourhood of
Calcutta.

BIOLOGY.--The zoaria of _S. indica_ are usually fixed to the roots of
duckweed or to the stems of other plants. They are often found together
with those of _P. punctata_. A slight infusion of brackish water into
the ponds in which it lives does not seem to be inimical to this
species, but I have found it in ponds in which nothing of the kind was
possible. It flourishes during the "rains" and, to judge from specimens
kept in an aquarium, is very short-lived. Major Walton found it growing
over a zoarium of _Hislopia lacustris_.


Subfamily B. LOPHOPINÆ.

The zoaria of this subfamily are never dendritic but form gelatinous
masses which, except in _Australella_, are cushion-shaped or sack-like.
With the possible exception of _Australella_, they possess to a limited
extent the power of moving along vertical or horizontal surfaces, but it
is by no means clear how they do so (see p. 172). The statoblasts are
remarkable for their large size, and it is noteworthy that
_Australella_, which is intermediate in structure between the
Plumatellinæ and the Lophopinæ, possesses statoblasts of intermediate
size. The swim-ring is always well developed, and fixed statoblasts are
unknown.

Only two genera (_Lophopodella_ and _Pectinatella_) have been definitely
proved to occur in India, but a third (_Lophopus_[BK]) is stated to have
been found in Madras. Should it be met with it will easily be recognized
by the upright position of its polypides when their tentacles are
expanded and by the fact that the statoblasts never bear marginal
processes.

     [Footnote BK: Only two species are known, _L. crystallinus_
     (Pallas) from Europe and N. America, with oval statoblasts
     that are produced and pointed at the two ends, and _L.
     jheringi_, Meissner from Brazil, with irregularly polygonal
     or nearly circular statoblasts.]


Genus 3. LOPHOPODELLA, _Rousselet_.

     _Lophopodella_, Rousselet, Journ. Quek. Micr. Club (2) ix,
     p. 45 (1904).

     _Lophopodella_, Annandale, Rec. Ind. Mus. v, p. 54 (1910).

TYPE, _Pectinatella carteri_, Hyatt.

_Zoarium._ The zoarium consists of a circular or oval mass of no great
size. Polyparia do not form compound colonies.

_Polypides._ The polypides lie semi-recumbent in the mass and never
stand upright in a vertical position.

_Statoblasts._ The statoblasts are of considerable size and normally
bear at both ends a series of chitinous processes armed with double rows
of small curved spinules.

As a rule the genus is easily recognized by means of the statoblasts,
but sometimes the processes at the ends of these structures are absent
or abortive and it is then difficult to distinguish them from those of
_Lophopus_. There is, however, no species of that genus known that has
statoblasts shaped like those of the Indian species of _Lophopodella_.

Three species of _Lophopodella_, all of which occur in Africa, have been
described; _L. capensis_ from S. Africa, which has the ends of the
statoblast greatly produced, _L. thomasi_ from Rhodesia, in which they
are distinctly concave, and _L. carteri_ from E. Africa, India and
Japan, in which they are convex or truncate.

The germination of the gemmule and the early stages in the development
of the polyparium of _L. capensis_ have been described by Miss Sollas
(Ann. Nat. Hist. (8) ii, p. 264, 1908).


37. Lophopodella carteri (_Hyatt_). (Plate III, figs. 4, 4_a_.)

     _Lophopus_ sp., Carter, Ann. Nat. Hist. (3) iii, p. 335, pl.
     viii, figs. 8-15 (1859).

     ? _Lophopus_ sp., Mitchell, Q. J. Micr. Sci. London (3) ii,
     p. 61 (1862).

     _Pectinatella carteri_, Hyatt, Comm. Essex Inst. iv, p. 203
     (footnote) (1866).

     _Pectinatella carteri_, Meissner, Die Moosthiere
     Ost-Afrikas, p. 4 (in Mobius's Deutsch-Ost-Afrika, iv,
     1898).

     _Lophopodella carteri_, Rousselet, Journ. Quek. Micr. Club,
     (2) ix, p. 47, pl. iii, figs. 6, 7 (1904).

     _Lophopus carteri_, Annandale, Rec. Ind. Mus. ii, p. 171,
     fig. 3 (1908).

     _Lophopodella carteri_, _id._, _ibid._ v, p. 55 (1910).

_Zoarium._ The zoarium as a rule has one horizontal axis longer than the
other so that it assumes an oval form when the polypides are expanded;
when they are retracted its outline is distinctly lobular. Viewed from
the side it is mound-shaped. The polypides radiate, as a rule in several
circles, from a common centre. The ectocyst is much swollen, hyaline and
colourless.

_Polypide._ The polypide has normally about 60 tentacles, the velum at
the base of which is narrow and by no means strongly festooned. The
stomach is yellow or greenish in colour. The extended part of the
polypide measures when fully expanded rather less than 3 mm., and each
limb of the lophophore about the same.

_Statoblast._ The statoblast is variable in shape and size but measures
on an average about 0.85 × 0.56 mm. The ends are truncate or
subtruncate; the capsule is small as compared with the swim-ring and as
a rule circular or nearly so. The processes at the two ends are variable
in number; so also are their spinules, which are arranged in two
parallel rows, one row on each side of the process, and are neither very
numerous nor set close together; as a rule they curve round through the
greater part of a circle and are absent from the basal part of the
process.

[Illustration: Fig. 46.--Lophopodella carteri (from Igatpuri Lake).

A=outline of a zoarium with the polypides expanded, as seen from below
through glass to which it was attached, × 4; B=outline of a zoarium with
the polypides highly contracted, as seen from above, × 4; C=statoblast,
× 75.]


37 _a._ Var. himalayana.

     _Lophopus lendenfeldi_, Annandale (_nec_ Ridley), J. As.
     Soc. Bengal, (n. s.) iii, 1907, p. 92, pl. ii, figs. 1-4
     (1907).

     _Lophopus lendenfeldi_ var. _himalayanus_, _id._, Rec. Ind.
     Mus. i, p. 147, figs. 1, 2 (1907).

     _Lophopus himalayanus_, _id._, _ibid._ ii, p. 172, fig. 4
     (1908).

This variety differs from the typical form in having fewer tentacles and
in the fact that the marginal processes of the statoblast are abortive
or absent.

_Pectinatella davenporti_, Oka[BL] from Japan is evidently a local race
of _L. carteri_, from the typical form of which it differs in having the
marginal processes of the statoblast more numerous and better developed.
The abortive structure of these processes in var. _himalayana_ points to
an arrest of development, for they are the last part of the statoblast
to be formed.

     [Footnote BL: Zool. Anz. xxxi, p. 716 (1907), and Annot.
     Zool. Japon. vi, p. 117 (1907).]

TYPES. The statoblasts mounted in Canada balsam by Carter and now in the
British Museum must be regarded as the types of the species named but
not seen by Hyatt. The types of the var. _himalayana_ are in the Indian
Museum and those of the subspecies _davenporti_ presumably in the
possession of Dr. Oka in Tokyo.

GEOGRAPHICAL DISTRIBUTION.--The typical form occurs in Bombay, the W.
Himalayas and possibly Madras, and its statoblasts have been found in E.
Africa; the var. _himalayana_ has only been taken in the W. Himalayas
and the subspecies _davenporti_ in Japan. Indian localities are:--BOMBAY
PRESIDENCY, Igatpuri Lake, W. Ghats (alt. _ca._ 2,000 feet); the Island
of Bombay (_Carter_): W. HIMALAYAS, Bhim Tal, Kumaon (alt. 4,500 feet).

BIOLOGY.--_L. carteri_ is found on the lower surface of stones and on
the stems and leaves of water-plants, usually in lakes or large ponds.
Although the zoaria do not form compound colonies by secreting a common
membrane or investment, they are markedly gregarious. The most closely
congregated and the largest zoaria I have seen were assembled amongst a
gelatinous green alga of the genus _Tolypothrix_[BM] (Myxophyceæ) that
grows on the vertical stems of a plant at the edge of Igatpuri Lake; it
is noteworthy that in this case the alga seemed to take the place of the
common investment of _Pectinatella burmanica_, in which green cells are
present in large numbers (p. 237). The zoaria of _L. carteri_ are able
to change their position, and I found that if a number of them were
placed in a bottle of water they slowly came together at one spot, thus
apparently forming temporary compound colonies. Before a movement of the
whole zoarium commences its base becomes detached from its support at
the anterior end (fig. 32, p. 172), but the whole action is extremely
slow and I have not been able to discover any facts that cast light on
its exact method of production. At Igatpuri statoblasts are being
produced in considerable numbers at the end of November, but many young
zoaria can be found in which none have as yet been formed.

     [Footnote BM: Prof. W. West will shortly describe this alga,
     which represents a new species, in the Journ. Asiat. Soc.
     Bengal, under the name _Tolypothrix
     lophopodellophila_.--_April 1911_.]

The larva of a fly of the genus _Chironomus_ is often found inhabiting a
tube below zoaria of _L. carteri_. It is thus protected from its enemies
but can protrude its head from beneath the zoarium and seize the small
animals on which it preys.


Genus 4. PECTINATELLA, _Leidy_.

     _Cristatella_, Leidy, P. Ac. Philad. v, p. 265 (1852).

     _Pectinatella_, _id._, _ibid._, p. 320.

     _Pectinatella_, Allman, Mon. Fresh-Water Polyzoa, p. 81
     (1857).

     _Pectinatella_, Hyatt, Proc. Essex Inst. v, p. 227, fig. 20
     (1867).

     _Pectinatella_, Kraepelin, Deutsch. Süsswasserbryozoen, i,
     p. 133 (1887).

     _Pectinatella_, Oka, Journ. Coll. Sci. Tokyo, iv, p. 89
     (1891).

TYPE, _Pectinatella magnifica_, Leidy.

This genus is closely allied to _Lophopodella_, from which it is often
difficult to distinguish young specimens. Adult zoaria are, however,
always embedded together in groups in a gelatinous investment which they
are thought to secrete in common[BN], and the statoblasts are entirely
surrounded by processes that bear curved spinules at their tips only.
The polypides have the same semi-recumbent position as those of
_Lophopodella_ but are larger than those of any species of
_Lophopodella_ or _Lophopus_ yet known. The statoblasts are larger than
those of any other Plumatellidæ.

     [Footnote BN: It is now perhaps open to doubt whether the
     investment is actually secreted by the polyzoon, for Prof.
     W. West has discovered in it the cells of an alga belonging
     to a genus which habitually secretes a gelatinous investment
     of its own (see p. 238, _post._).--_April 1911._]

The type-species was originally found in N. America but has since been
taken in several localities in continental Europe. Except this and the
Indian form only one species is known, namely _P. gelatinosa_ from
Japan. _P. magnifica_ has circular statoblasts with long marginal
processes, while in _P. gelatinosa_ the statoblasts are subquadrate and
in _P. burmanica_ almost circular, both Asiatic forms having very short
marginal processes.

The compound colonies formed by _Pectinatella_ are often of great size.
Those of _P. gelatinosa_ are sometimes over 2 metres in length, while
those of _P. burmanica_ in the Sur Lake appeared to be only limited as
regards their growth by the shallowness of the water in which the reeds
to which they were attached were growing. Some were observed that were
over 2 feet long.


38. Pectinatella burmanica, _Annandale_. (Plate III, fig. 5.)

     _Pectinatella burmanica_, Annandale, Rec. Ind. Mus. ii,
     p. 174, fig. 5 (1908).

     _Pectinatella burmanica_, _id._, _ibid._ v, p. 56 (1910).

     _Pectinatella burmanica_, _id._, Spol. Zeyl. vii, p. 63,
     pl. i, fig. 3 (1910).

_Zoarium._ The zoaria are circular or nearly so except when about to
undergo division, in which case they are constricted in the middle. As a
rule they measure nearly an inch (2 cm.) in diameter. The polypides have
a definite arrangement in each zoarium, being divided into four groups,
each of which has a fan-like form. In the first place they are separated
into two main divisions in a line running through the centre of the
zoarium, and secondly each main division is separated into two
subordinate ones in a line running across the other at right angles. The
number of zoaria joined together in a single compound colony is very
variable; sometimes there are only about half a dozen and sometimes
several hundreds. The common investment in living colonies is often as
much as two inches thick and has a translucent dark greenish colour due
to the presence in it of green cells.

[Illustration: Fig. 47.--_Pectinatella burmanica._

A=polypide with the lophophore expanded, × 15; _a_=oesophagus;
_b_=cardiac limb of stomach; _c_=stomach; _d_=rectum; _e_=anus;
_f_=funiculus. [The muscles are omitted and the external tubercles are
only shown on part of the polypide. The specimen is from the Sur Lake,
Orissa.] B=statoblast from Ceylon, × 35.]

_Polypide._ The polypide can be extruded for a distance of at least 5
mm. Its whole external surface is covered with minute tubercles. There
are about 90 tentacles, which are long and slender, the velum at their
base being narrow and almost straight. The stomach is of considerable
stoutness.

_Statoblast._ The statoblasts are of large size, measuring from 1 to
1.75 mm. in diameter. In form they are almost circular, but one side is
always slightly flattened. The marginal processes are very short and
bear a single pair of hooks at the tip. The capsule is circular and
small as compared with the free part of the swim-ring.

TYPE in the Indian Museum.

_P. burmanica_ is evidently a near relation of _P. gelatinosa_, Oka,
from Japan, differing from that species in the shape of the statoblasts
and in having much longer tentacles. The arrangement of the polypides in
the zoarium and the general structure of the statoblasts are very
similar in the two species.

GEOGRAPHICAL DISTRIBUTION.--_P. burmanica_ was originally described from
a swamp at Kawkareik in the Amherst district of Tenasserim but has also
been found in the Sur Lake near Puri in Orissa. Dr. A. Willey obtained
specimens from a pool by the roadside between Maradankadewela and
Galapitagala, at the foot of Ritigala, N. Central Province, Ceylon.

BIOLOGY.--The first specimen obtained was a statoblast fixed to a tube
of the oligochæte worm _Aulophorus tonkinensis_ taken at Kawkareik in
March. At the same time young zoaria, which did not yet possess a common
investment, were found on a leaf growing on a twig which drooped into
the water. Large compound colonies were taken in Orissa in October. They
completely encased the stems of reeds, thus forming hollow cylinders,
but slipped from their supports when the reeds were pulled out of the
water. In life they resembled gelatinous algæ rather than animals and
exhibited a striking similarity to masses of zoaria of _Lophopodella
carteri_ surrounded by such algæ. Some of the colonies were evidently
dying and contained few polypides in a living condition, but many
statoblasts; others were in a flourishing condition and were producing
larvæ and statoblasts simultaneously.

A piece of a colony full of larvæ was placed before midday in an
aquarium, which was kept in a shady verandah. Large numbers of larvæ
were set free almost immediately. They measured about 2 mm. in length
and were distinctly pear-shaped; each contained a pair of polypides,
which occupied a comparatively small part of the interior, the whole of
the broader half being hollow. The larvæ swam slowly, broad-end-first,
by means of the cilia with which their surface was covered, occasionally
gyrating on their long axis and always adopting an erratic course.
Towards evening they showed signs of settling down, frequently touching
the glass of the aquarium with their broad ends and sometimes remaining
still in this position for some minutes. Many attempts were, however,
made before fixation was completed, and this did not occur until after
nightfall. By next morning every larva was fixed to the glass and had
everted its two polypides. Unfortunately I was not able to trace the
development further, but young compound colonies were found in which the
secretion of the common investment had just commenced. The zoaria in
these colonies measured about 1 cm. in diameter and already contained
many polypides each.

Oka has described the development from the statoblast of the allied
Japanese species. He found that each statoblast produced in the first
instance a single polypide, and that the statoblasts, which were
produced in autumn, lay dormant through the winter and germinated in
spring. As the Sur Lake begins to undergo desiccation as soon as the
"rains" cease, the statoblasts in it probably do not germinate until the
break of the next "rains" about the middle of June. I have had dried
statoblasts in my possession for over two years. Their cellular contents
appear to be in good condition, although the cells show no signs of
development; but they have not germinated in my aquarium, in which some
of them have now been kept for more than six months.

The green cells of the common investment are peculiar bodies that
deserve further study than it has yet been possible to devote to them.
Each cell is of ovoid form, varying somewhat in size but as a rule
measuring about 0.03 × 0.008 mm. There can be no doubt that these bodies
represent a stage in the life-history of an alga[BO]. Diatoms, bacilli
and other minute plants are often present in the membrane as well as the
characteristic green cells, but do not form a constant feature of it.

     [Footnote BO: Professor W. West identifies this algæ as
     _Dactylococcopsis pectinatellophila_, new species. It will
     be described, before the publication of this book, in the
     Journ. As. Soc. Bengal (1911). Prof. West has found,
     associated more or less fortuitously with _P. burmanica_,
     another alga, namely _Microcystis orissica_, also a new
     species.--_April 1911._]




APPENDIX TO THE VOLUME.


HINTS ON THE PREPARATION OF SPECIMENS.

_To preserve Spongillidæ._--Spongillidæ must be preserved dry or in very
strong alcohol. Formalin should not be used.

_To clean siliceous sponge spicules._--Place small fragments of the
dried sponge (if alcohol is present, the reaction is apt to be violent)
in a test tube, cover them with strong nitric acid and boil over the
flame of a Bunsen burner or small spirit lamp until the solid particles
disappear. Add a large quantity of water to the acid and filter through
pure cellulose filter-paper, agitating the liquid repeatedly. Pass clean
water in considerable quantities through the filter-paper and dry the
latter carefully; place it in a spirally coiled wire and ignite with a
match, holding the wire in such a way that the spicules released by the
burning of the paper fall into a suitable receptacle. They may then be
picked up with a camel's-hair brush and mounted in Canada balsam.

_To examine the skeleton of a Spongillid._--Cut thin hand-sections with
a sharp scalpel, dehydrate if necessary, and mount in Canada balsam.

_To prepare gemmules for examination._--Place the gemmules dry in a
watch-glass with a few drops of strong nitric acid. When gas is given
off freely add water in considerable quantities. Remove the gemmules
with a camel's-hair brush to clean water, then to 50%, 70%, 90% and
absolute alcohol in succession, leaving them for an hour in each
strength of spirit. Clear with oil of cloves and mount in Canada balsam.

_To ascertain the presence of bubble-cells in the parenchyma of a
Spongillid._--Tease up a small piece of the sponge with a pair of
needles, mount under a thin cover-slip in strong spirit, and examine
under a high power of the microscope.

_To preserve Hydra in an expanded condition._--Place the polyp in a
watch-glass of clean water and wait until its tentacles are expanded.
Heat a few drops of commercial formaldehyde and squirt the liquid while
still hot at the _Hydra_, which will be killed instantaneously. Remove
it to a solution of formaldehyde and spirit of the following formula:--

     Commercial formaldehyde      1 part.
     Absolute alcohol             3 parts.
     Distilled water              7 parts.

Then pass the _Hydra_ through 50% and 70% alcohol and keep in 90%.

_To examine the capsules of the nettle-cells._--Place a living _Hydra_
in a small drop of water on a slide and press a thin cover-slip down
upon it.

_To preserve freshwater polyzoa in an expanded condition._--Place the
polyzoa in a glass tube full of clean water and allow them to expand
their tentacles. Drop on them gradually when they are fully expanded a
2% aqueous solution of cocaine, two or three drops at a time, until
movement ceases in the tentacles. Then pour commercial formaldehyde into
the tube in considerable quantities. Allow the whole to stand for half
an hour. If it is proposed to stain the specimens for anatomical
investigation, they should then be removed through 50% and 70% to 90%
alcohol. If, on the other hand, it is desired to keep them in a
life-like condition they may be kept permanently in a solution of one
part of commercial formaldehyde in four parts of water. Care must be
taken that the process of paralyzing the polypides is not unduly
prolonged, and it is always as well to preserve duplicate specimens in
spirit or formalin with the lophophore retracted.

_To prepare statoblasts for examination._--Place the statoblasts for a
few minutes in strong nitric acid. Then remove the acid with water, pass
through alcohol, clear with oil of cloves, and mount in a small quantity
of Canada balsam under a cover-slip, taking care that the statoblasts
lie parallel to the latter.




ADDENDA.


The following addenda are due mainly to an expedition to the lakes of
Kumaon in the W. Himalayas undertaken by Mr. S. W. Kemp in May, 1911.


PART I.


Genus SPONGILLA.


Subgenus EUSPONGILLA (p. 69).

1 a. Spongilla lacustris, subsp. reticulata (p. 71).

Specimens were taken in the lake Malwa Tal (alt. 3600 feet) in Kumaon,
while others have recently been obtained from the Kalichedu
irrigation-tank in the Pagnor _talug_ of the Nellore district, Madras
(_G. H. Tipper_).

4. Spongilla cinerea (p. 79).

Specimens were taken in Naukuchia Tal (alt. 4200 feet) in Kumaon. They
have a pale yellow colour when dry. This sponge has not hitherto been
found outside the Bombay Presidency.


Subgenus EUNAPIUS (p. 86).

8. Spongilla carteri (p. 87).

Specimens were taken in Bhim Tal (alt. 4450 feet) and Sat Tal (alt. 4500
feet). Some of them approach the variety _cava_ in structure.


Subgenus STRATOSPONGILLA (p. 100).

12. Spongilla bombayensis (p. 102).

Add a new variety:--

13 a. Var. pneumatica, nov.

  (i.)   The sponge forms a flat layer of a pale brownish colour
         as a rule with short and very delicate vertical branches.
         In one specimen it takes the form of an elegant cup
         attached, only at the base, to a slender twig.

  (ii.)  The gemmules are covered, outside the spicules, by a
         thick pneumatic coat of irregular formation and with
         comparatively large air-spaces.

  (iii.) The gemmule-spicules are regularly sausage-shaped.

TYPES in the Indian Museum.

HABITAT. Naukuchia Tal (alt. 4200 feet), Kumaon, W. Himalayas (_S. W.
Kemp_).


Genus EPHYDATIA (p. 108).

After _Ephydatia meyeni_, p. 108, add:--


Ephydatia fluviatilis, _auct._

     ? _Ephydatia fluviatilis_, Lamouroux, Encyclop. Méthod. ii,
     p. 327 (1824).

     _Spongilla fluviatilis_, Bowerbank (_partim_), Proc. Zool.
     Soc. London, 1863, p. 445, pl. xxxviii, fig. 1.

     _Ephydatia fluviatilis_, J. E. Gray (_partim_), Proc. Zool.
     Soc. London, 1867, p. 550.

     _Meyenia fluviatilis_, Carter (_partim_), Ann. Nat. Hist.
     (5) vii, p. 92, pl. vi, fig. 11 _a_, _b_ (1881).

     _Ephydatia fluviatilis_, Vejdovsky, Abh. k. Böhm.
     Gesellschaft Wiss. xii, p. 24, pl. i, figs. 1, 2, 7, 10, 14,
     19 (1883).

     _Ephydatia fluviatilis_, _id._, P. Ac. Philad. 1887, p. 178.

     _Meyenia fluviatilis_ var. _gracilis_, Potts, _ibid._, p.
     224.

     _Meyenia robusta_, _id._, _ibid._, p. 225, pl. ix, fig. 5.

     _Ephydatia fluviatilis_, Weltner, Arch. Naturg. Berlin, 1895
     (i) p. 122.

     _Ephydatia robusta_, Annandale, Journ. As. Soc. Bengal,
     1907, p. 24, fig. 7.

     _Ephydatia fluviatilis_, Weltner, in Brauer's
     Süsswasserfauna Deutschlands xix, Süsswasserschwämme, p.
     185, figs. 316, 317 (1909).

     _Ephydatia fluviatilis_, Annandale, P. U. S. Mus. xxxviii,
     p. 649 (1910).

[Many more references to this common species might be cited, but those
given above will be sufficient.]

This species only differs from _E. meyeni_ in the following
characters:--

  (i.)   there are no bubble-cells in the parenchyma;

  (ii.)  there is less spongin in the skeleton, which is less compact;

  (iii.) the gemmule-spicules are longer, the shafts being as a rule
         longer than the diameter of the rotulæ;

  (iv.)  the gemmules are armed with a single row of regularly
         arranged spicules embedded in pneumatic tissue with
         minute air-spaces.

The sponge is a variable one and several "varieties" have been described
from different parts of the world. My Indian specimens come nearest to
the form described by Potts as _Meyenia robusta_, but have rather more
slender skeleton-spicules and more elongate gemmule-spicules. The latter
also appear to be less frequently "monstrous."

TYPE ?

GEOGRAPHICAL DISTRIBUTION.--_E. fluviatilis_ is widely distributed in
Europe and occurs in N. America,[BP] S. Africa (var. _capensis_,
Kirkpatrick), Australia, and Japan. Specimens were obtained by Mr. Kemp
from several lakes in Kumaon, namely Naukuchia Tal (alt. 4200 feet),
Bhim Tal (4450 feet), Sat Tal (4500 feet), and Naini Tal (6300 feet).
The gemmules from Bhim Tal referred by me to _E. robusta_ (Potts) also
belong to this species.

     [Footnote BP: Most of the forms assigned by Potts to this
     species belong to the closely allied _E. mülleri_
     (Lieberkühn).]

_Biology._ The external form of the sponge is due in great part to its
environment. Specimens on small stones from the bottom of the Kumaon
Lakes consist of thin disk-like films, often not more than a few
centimetres in diameter and a few millimetres thick: others, growing on
thin twigs, are elevated and compressed, resembling a cockscomb in
appearance, while others again form nodules and masses of irregular form
among the branches of delicate water-weeds. Some of these last are
penetrated by zoaria of _Fredericella indica_.

Weltner has published some very interesting observations on the seasonal
variation of minute structure in European representatives of the species
(Arch. Naturg. Berlin, lxxiii (i), p. 273 1907) and has discussed the
formation of the abnormal spicules that sometimes occur (_ibid._ lxvii
(Special Number), p. 191, pls. vi, vii, figs. 27-59, 1901).


Genus CORVOSPONGILLA (p. 122).

After _Corvospongilla burmanica_, p. 123, add a new species:--


Corvospongilla caunteri, nov.

_Sponge_ forming thin films of considerable area not more than 3 or 4
mm. thick, of a bright green colour, moderately hard but friable. The
surface smooth; oscula inconspicuous, surrounded by shallow and
ill-defined radiating furrows; a very stout basal membrane present.

[Illustration: Fig. 48.--_Corvospongilla caunteri_ (type, from Lucknow).

A=Gemmule; B=gemmule-spicules; C=flesh-spicules; D=Skeleton-spicules.]

_Skeleton_ reticulate but almost devoid of spongin, the reticulations
close but formed mainly by single spicules; skeleton-fibres barely
distinguishable. A close layer of spicules lying parallel to the basal
membrane.

_Spicules._ Skeleton-spicules variable in size and shape, almost
straight, as a rule smooth, moderately stout, blunt or abruptly pointed;
sometimes roughened or spiny at the tips, often sharply pointed.
Flesh-spicules minute, few in number, with smooth, slender shafts which
are variable in length, never very strongly curved; the terminal spines
relatively short, not strongly recurved. Gemmule-spicules
amphistrongylous or amphioxous, irregularly spiny, slender, of variable
length.

_Gemmules_ free in the substance of the sponge, spherical or somewhat
depressed, very variable in size but never large, having a thick
external pneumatic coat in which the air-spaces are extremely small and,
inside this coat, a single rather sparse layer of spicules lying
parallel to the gemmule. A single depressed aperture present.

TYPE in the Indian Museum.

HABITAT. Hazratganj, Lucknow; on piers of bridge in running water (_J.
Caunter_, 29-30. iv. 11).

The structure of the gemmules of this species differs considerably from
that in any other known species of the genus, in which these structures
are usually adherent and devoid of a true pneumatic coat. In some of the
gemmules before me this coat measures in thickness about 1/9 of the
total diameter of the gemmule. _C. caunteri_ is the first species of
_Corvospongilla_ to be found in the Indo-Gangetic plain.


PART II.


Genus HYDRA (p. 147).


25. Hydra oligactis (p. 158).

Mr. Kemp found this species common in Bhim Tal in May. His specimens,
which were of a reddish-brown colour in life, appear to have been of
more vigorous constitution than those taken by Major Stephenson in
Lahore. Some of them had four buds but none were sexually mature.


PART III.


Genus FREDERICELLA (p. 208).


28. Fredericella indica (p. 210).

This species is common in some of the Kumaon lakes, in which it grows,
at any rate at the beginning of summer, much more luxuriantly than it
does in the lakes of the Malabar Zone in autumn, forming dense bushy
masses on the under surface of stones, on sticks, &c. The vertical
branches often consist of many zooecia. Mr. Kemp took specimens in Malwa
Tal, Sath Tal, and Naini Tal (alt. 3600-6300 feet).


Genus PLUMATELLA (p. 212).


30. Plumatella emarginata (p. 220).

Mr. Kemp took bushy masses of this species in Malwa Tal and Bhim Tal.


32. Plumatella diffusa (p. 223).

This species is common in Malwa Tal and Bhim Tal in May.


33. Plumatella allmani (p. 224).

Mr. Kemp only found this species in Malwa Tal, in which (at any rate in
May) it appears to be less abundant than it is in Bhim Tal in autumn.
Mr. Kemp's specimens belong to the form called _P. elegans_ by Allman.


34. Plumatella tanganyikæ (p. 225).

Specimens taken by Mr. Kemp, somewhat sparingly, in Bhim Tal and Sath
Tal in May exhibit a somewhat greater tendency towards uprightness of
the zooecia than those I found in autumn in Igatpuri lake. The ectocyst
is, in the former specimens, of a deep but bright reddish-brown. The
zoaria are attached to twigs and small stones.


Genus STOLELLA (p. 229).

After Stolella indica, p. 229, add a new species:--


Stolella himalayana, nov.

This species may be distinguished from _S. indica_ by (i) its entirely
recumbent zooecia, and (ii) the lateral branches of its zoarium.

[Illustration: Fig. 49.--_Stolella himalayana_ (types, from the Kumaon
lakes).

A. The greater part of a young zoarium. B. Part of a much older
zoarium.]

_Zoarium_ entirely recumbent, consisting of zooecia joined together,
often in groups of three, by slender, transparent, tubular processes.
These processes are often of great relative length; they are formed by a
modification of the posterior or proximal part of the zooecia, from
which they are not separated by a partition, and they increase in length
up to a certain point more rapidly than the zooecia proper. A zooecium
often gives rise first to an anterior daughter-zooecium, the proximal
part of which becomes elongate and attenuated in due course, and then to
a pair of lateral daughter-zooecia situated one on either side. As a
result of this method of budding a zoarium with a close superficial
resemblance to that of _Paludicella_ is at first produced, but as the
colony increases in age and complexity this resemblance largely
disappears, for the zooecia and their basal tubules grow over one
another and often become strangely contorted (fig. 49).

_Zooecia_ elongate and slender, flattened on the ventral, strongly
convex on the dorsal surface; rather deep in proportion to their
breadth; the ectocyst colourless, not very transparent except on the
stolon-like tubular part; dorsal keel and furrow as a rule absent;
orifice unusually inconspicuous, situated on a tubercle on the dorsal
surface.

_Polypide_ stout and short; the tip of the fundus of the stomach capable
of very complete constriction; the retractor muscles unusually short and
stout.

_Statoblasts._ Only free statoblasts have been observed. They resemble
those of _S. indica_, but are perhaps a little longer and more elongate.

TYPES in the Indian Museum.

The discovery of this species makes it necessary to modify the diagnosis
of the genus, the essential character of which, as distinguishing it
from _Plumatella_, is the differentiation of the proximal part of some
or all of the zooecia to form stolon-like tubules. From _Stephanella_,
Oka, it is distinguished by the absence of a gelatinous covering, and by
the fact that all the zooecia are attached, at least at the base, to
some extraneous object.

HABITAT. Malwa Tal, Kumaon (alt. 3600 feet), W. Himalayas (_Kemp_, May
1911).

BIOLOGY. Mr. Kemp took three specimens, all attached to the lower
surface of stones. They contained few statoblasts and were evidently in
a condition of vigorous growth. Between the lateral branches new
polyparia were developing in several instances from free statoblasts,
each of which appeared to contain two polypides.




ALPHABETICAL INDEX.


All names printed in italics are synonyms.

When more than one reference is given, the page on which the description
occurs is indicated by thickened numerals.

  alba (Euspongilla) (Spongilla), 8, 9.
  alba (Spongilla), 4, 22, 63, ~76~.
  alba _var._ bengalensis (Spongilla), 4, 22, 63, ~77~.
  alba _var_. cerebellata (Spongilla), 22, 63, ~76~.
  _alba_ var. _marina_ (_Spongilla_), ~77~.
  _Alcyonella_, 212.
  Alcyonellea, 185.
  allmani (Plumatella), 7, 8, 9, 23, 188, ~224~, 246.
  _allmani_ var. _diffusa_ (_Plumatella_), 223.
  _allmani_ var. _dumortieri_ (_Plumatella_), 222.
  _attenuata_ (_Hydra_), 148, 158.
  _aurantiaca_ (_Hydra_), 148.
  aurea (Pectispongilla), 9, 22, 63, ~106~.
  aurea _var._ subspinosa (Pectispongilla), 63, ~107~.

  _benedeni_ (_Alcyonella_), 220.
  bengalensis (Bowerbankia), 189.
  bengalensis (Membranipora), 23.
  bengalensis (Spongilla), 77.
  bengalensis (Victorella), 4, 8, 9, 23, 187, ~195~.
  blembingia (Ephydatia), 54.
  bogorensis (Ephydatia), 54.
  _bombayensis_ (_Plumatella_), 225.
  bombayensis (Spongilla), 22, 63, 100, ~102~, 241.
  bombayensis (Stratospongilla) (Spongilla), 8, 9.
  Bowerbankia, 187, ~189~.
  _brunnea_ (_Hydra_), 148.
  burmanica (Corvospongilla), 8, 22, 64, ~122~.
  burmanica (Pectinatella), 8, 10, 23, 188, ~235~.

  calcuttana (Spongilla), 96.
  _cambodgiensis_ (_Norodonia_), 202.
  _Carterella_, 108.
  carteri (Eunapius) (Spongilla), 7, 8, 9, 10.
  _carteri_ (_Eunapius_), 87.
  carteri (Lophopodella), 7, 8, 23, 188, ~232~, 233.
  _carteri_ (_Lophopus_), 232.
  _carteri_ (_Pectinatella_), 231,
  carteri (Spongilla), 4, 22, 63, 86, ~87~, 241.
  carteri _var._ cava (Spongilla), 22, 63.
  carteri _var._ himalayana (Lophopodella), 23, 188.
  carteri _var._ lobosa (Spongilla), 22, 63.
  carteri _var._ mollis (Spongilla), 22, 63.
  caudata (Bowerbankia), 189.
  caudata _subsp._ bengalensis (Bowerbankia), 23, 189.
  caunteri (Corvospongilla), 243.
  cava (Spongilla), 88.
  cerebellata (Spongilla), 76.
  ceylonensis (Irene), 22, 140.
  Cheilostomata, 184.
  Chlorella, 50.
  cinerea (Euspongilla) (Spongilla), 9.
  cinerea (Spongilla), 22, 63, 72, 79, 241.
  clementis (Stratospongilla) (Spongilla), 53.
  coggini (Stratospongilla) (Spongilla), 53.
  colonialis (Loxosomatoides), 23.
  _contecta_ (_Spongilla_), 95.
  _coralloides_ (_Plumatella_), 217.
  Corvospongilla, 64, ~122~, 243.
  crassior (Spongilla), 98.
  crassissima (Eunapius) (Spongilla), 9.
  crassissima (Spongilla), 4, 22, 63, ~98~.
  crassissima _var._ crassior (Spongilla), 23, 63.
  _crateriformis_ (_Meyenia_), 83.
  _crateriformis_ (_Ephydatia_), 83, 84.
  crateriformis (Euspongilla) (Spongilla), 8, 9.
  _crateriformis_ (_Meyenia_), 83.
  crateriformis (Spongilla), 22, 63, ~83~.
  _Cristatella_, 235.
  Cristatellina, 206.
  Ctenostomata, 184, 185, 187, ~189~.
  Cyclostomata, 184.

  decipiens (Spongilla), 54, 96, ~97~.
  diffusa (Plumatella), 7, 8, 9, 23, 188, ~223~, 245.
  _di[oe]cia_ (_Hydra_), 158.
  Dosilia, 64, ~110~.

  _Echinella_, 199.
  _elegans_ (_Plumatella_), 224.
  Eleutheroblastea, 146, 147.
  emarginata (Plumatella), 4, 8, 9, 10, 23, 188, 218, ~220~, 245.
  _emarginata_ var. _javanica_ (_Plumatella_), 221.
  Entoprocta, 183.
  Ephydatia, 64, ~108~, 242.
  _erinaceus_ (_Spongilla_), 114.
  Eunapius, 63, ~86~, 241.
  Euspongilla, 63, 67, ~69~, 241.

  filamentata (Syncoryne), 22, 140.
  fluviatilis (Ephydatia), 109, ~242~.
  _fluviatilis_ (_Meyenia_), 242.
  fluviatilis (Spongilla), 108, 242.
  _fluviatilis_ var. _gracilis_ (_Meyenia_), 242.
  fortis (Ephydatia), 52, 53.
  fragilis (Spongilla), ~95~, 96.
  fragilis _subsp._ calcuttana (Eunapius) (Spongilla), 9.
  fragilis _subsp._ calcuttana (Spongilla), 22, 63.
  fragilis _subsp._ decipiens (Spongilla), 22, 63.
  Fredericella, 188, ~208~, 245.
  FREDERICELLIDÆ, 188, ~208~.
  _friabilis_ (_Spongilla_), 87.
  fruticosa (Plumatella), 4, 7, 8, 9, 23, 188, ~217~, 218.
  _fusca_ (_Hydra_), 158, 159.

  Gecarcinucus, 10.
  gemina (Eunapius) (Spongilla), ~8~.
  gemina (Spongilla), 22, 63, ~97~.
  _glomerata_ (_Spongilla_), 95.
  _grisea_ (_Hydra_), 148, 149.
  Gymnolæmata, 184, 187.

  Halichondrina, 65.
  hemephydatia (Euspongilla) (Spongilla), 8.
  hemephydatia (Spongilla), 22, 63, ~82~.
  _hexactinella_ (_Hydra_), 148.
  himalayana (Lophopodella), 233.
  himalayana (Stolella), 246.
  _himalayanus_ (_Lophopus_), 233.
  Hislopia, 187, ~199~.
  Hislopidées, 199.
  HISLOPIIDÆ, 187, ~199~.
  Homodiætidæ, 191.
  _Hyalinella_, 212.
  Hydra, 146, ~147~, 245.
  Hydraidæ, 147.
  HYDRIDÆ, 146, 147.
  hydriforme (Polypodium), 142.
  Hydrozoa, 146.

  _indica_ (_Ephydatia_), 83.
  indica (Fredericella), 9, 23, 188, ~209~, 245.
  indica (Spongilla), 22, 63, ~100~.
  indica (Stolella), 4, 9, 23, 188, ~229~.
  indica (Stratospongilla), (Spongilla), 9.

  javanica (Plumatella), 4, 8, 9, 23, 188, ~221~, 222.

  kawaii (Limnocodium), 141.

  lacroixii (Membranipora), 23.
  lacustris (Cordylophora), 141.
  _lacustris_ (_Euspongilla_), 69.
  lacustris (Hislopia), 4, 8, 9, 23, 187, 199, ~202~, 204.
  lacustris (Spongilla), 63, 67, ~69~.
  lacustris _subsp._ moniliformis (Hislopia), 9, 23, 187.
  lacustris _subsp._ reticulata (Spongilla), 4, 8, 9, 22, 63, ~71~, 241.
  _lacustris_ var. _bengalensis_ (_Spongilla_), 77.
  lapidosa (Corvospongilla), 9, 22, 64, ~124~.
  _lapidosa_ (_Spongilla_), 124.
  latouchiana (Trochospongilla), 4, 8, 9, 22, 64, ~115~.
  _leidyi_ (_Trochospongilla_), 115.
  _lendenfeldi_ (_Lophopus_), 233.
  _lendenfeldi_ var. _himalayanus_ (_Lophopus_), 233.
  lobosa (Spongilla), 89.
  LOPHOPINÆ, 188, 211, ~231~.
  Lophopodella, 8, 188, ~231~.
  _Lophopus_, 8, 232.
  _lordii_ (_Spongilla_), 95.
  loricata (Spongilla), ~122~.
  _loricata_ var. _burmanica_, (_Spongilla_), 122.
  _lucifuga_ (_Plumatella_), 217, 220, 224.

  magnifica (Pectinatella), 235.
  meyeni (Ephydatia), 7, 9, 17, 22, 64, ~108~.
  _meyeni_ (_Spongilla_), 108.
  _Meyenia_, 108, 113.
  microsclerifera (Euspongilla) (Spongilla), 53.
  mollis (Spongilla), 88.
  moniliformis (Hislopia), 204.
  _mon[oe]cia_ (_Hydra_), 158.
  _morgiana_ (_Spongilla_), 95.
  _mülleri_ (_Ephydatia_), 109, 243.
  _mülleri_ subsp. _meyeni_ (_Ephydatia_), 109.

  _Norodonia_, 199.

  oligactis (Hydra), 7, 22, 146, ~158~, 159, 245.
  _orientalis_ (_Hydra_), 148, 149.
  _ottavænsis_ (_Spongilla_), 95.

  _pallens_ (_Hydra_), 148.
  Paludicella, 187, ~192~.
  PALUDICELLIDÆ, 187, ~191~.
  Paludicellidées, 191.
  Paludicellides, 191.
  Paludicellina, 186, 187, ~190~.
  paulula (Spongilla), 120.
  _pavida_ (_Victorella_), 194, 195.
  Pectinatella, 188, ~235~.
  pectinatellophila (Dactyloccopsis), 238.
  Pectispongilla, 63, ~106~.
  pennsylvanica (Trochospongilla), 9, 22, 64, ~118~.
  _pennsylvanica_ (_Tubella_), 118.
  _pentactinella_ (_Hydra_), 149.
  philippinensis (Euspongilla) (Spongilla), 53.
  phillottiana (Trochospongilla), 4, 8, 9, 22, 64, ~117~.
  Phylactolæmata, 185, 188, ~206~.
  Plumatella, 188, 208, ~212~, 245.
  PLUMATELLIDÆ, 188, ~211~.
  Plumatellina, 188, ~206~.
  PLUMATELLINÆ, 188, 211, ~212~.
  plumosa (Dosilia), 8, 9, 22, 64, ~111~.
  _plumosa_ (_Ephydatia_), 111.
  _plumosa_ (_Meyenia_), 111.
  _plumosa_ (_Spongilla_), 111.
  pneumatica (Stratospongilla) (Spongilla), 241.
  _polypus_ (_Hydra_), 148, 159.
  Polyzoa, 183.
  _princeps_ (_Plumatella_), 220.
  _princeps_ var. _emarginata_ (_Plumatella_), 220.
  _princeps_ var. _fruticosa_ (_Plumatella_), 217.
  proliferens (Euspongilla) (Spongilla), 8, 9, 10.
  proliferens (Spongilla), 4, 8, 22, 63, ~72~.
  Proterospongia, 27.
  _punctata_ (_Hyalinella_), 228.
  punctata (Plumatella), 9, 188, ~227~.

  _repens_ (_Plumatella_), 217, 223.
  reticulata (Spongilla), 71.
  _rhætica_ (_Hydra_), 158.
  _robusta_ (_Ephydatia_), 109, 242.
  _robusta_ (_Meyenia_), 242.
  _roeselii_ (_Hydra_), 158.
  ryderi (Microhydra), 141.

  schilleriana (Sagartia), 2, 22, 140.
  schilleriana _subsp_. exul (Sagartia), 22.
  _sibirica_ (_Spongilla_), 95.
  _sinensis_ (_Norodonia_), 202.
  sinensis (Stratospongilla) (Spongilla), 53.
  _socialis_ (_Hydra_), 158.
  sowerbii (Limnocodium), 141.
  Spongilla, 63, ~67~, 86, 241.
  Spongilladæ, 65.
  SPONGILLIDÆ, 65.
  Stolella, 188, ~229~, 246.
  Stolonifera, 185.
  Stratospongilla, 63, ~100~, 241.
  _stricta_ (_Plumatella_), 217.
  subspinosa (Pectispongilla), 107.
  sumatrana (Stratospongilla) (Spongilla), 53.

  tanganyikæ (Limnocnida), 142.
  tanganyikæ (Plumatella), 9, 23, 188, ~225~, 246.
  Trachospongilla, 64, ~113~.
  _Trachyspongilla_, 108.
  travancorica (Euspongilla) (Spongilla), 9.
  travancorica (Spongilla), 22, 63, ~81~.
  _trembleyi_ (_Hydra_), 148.
  Tubella, 64, 113, ~120~.

  ultima (Spongilla), 22, 63, ~105~.
  ultima (Stratospongilla) (Spongilla), 9.

  VESICULARIDÆ, 189.
  Vesicularina, 186, 187, ~189~.
  _vesicularis_ (_Hyalinella_), 228.
  _vesicularis_ (_Plumatella_), 227, 228.
  vesparioides (Tubella), 8, 22, 64, ~120~.
  vesparium (Tubella), 54.
  vestita (Bimeria), 22, 139.
  Victorella, 189, ~194~.
  Victorellidæ, 191.
  Victorellides, 191.
  viridis (Hydra), 147.
  _vitrea_ (_Hyalinella_), 228.
  _vitrea_ (_Plumatella_), 227, 228.
  vulgaris (Hydra), 4, 8, 9, 10, 22, 130, 146, ~148~, 149, 158.

  whiteleggei (Cordylophora), 141.

  yunnanensis (Euspongilla) (Spongilla), 53.




  PLATE I.

  SPECIMENS OF _Spongilla_ PRESERVED IN SPIRIT.


  Figs. 1-3. _S. (Euspongilla) alba_ var. _bengalensis_ (nat.
     size) from ponds of brackish water at Port Canning in the
     delta of the Ganges. Fig. 1 represents the type-specimen of
     the variety, and was taken in the winter of 1905-6. Figs. 2
     and 3 represent specimens taken in the same ponds in the
     winters of 1907 and 1908 respectively.

  Fig. 4. _Spongilla_ sp. (? abnormal form of _S. (Eunapius
     carteri_)) from an aquarium in Calcutta (× 10).

  [Illustration: Freshwater Sponges.                     Plate I.
  A. C. Chowdhary, del.                               SPONGILLA.]




  PLATE II.

  PHOTOGRAPHS OF DRIED SPECIMENS OF _Spongilla_, _Tubella_, AND
  _Corvospongilla_.


  Fig. 1. Part of a large specimen of _S. (Eunapius) carteri_
     from Calcutta, to show the conspicuous rounded oscula
     (reduced).

  Fig. 2. Gemmules of _S. (Stratospongilla) bombayensis_ on a
     stone from the edge of Igatpuri Lake, Bombay Presidency
     (nat. size).

  Fig. 3. Part of one of the type-specimens of _S.
     (Stratospongilla) ultima_ from Cape Comorin, Travancore, to
     show the star-shaped oscula (slightly enlarged).

  Fig. 4. Part of the type specimen of _T. vesparioides_
     (external membrane destroyed), to show the reticulate
     skeleton and the numerous gemmules (nat. size).

  Fig. 5. Part of a schizotype of _C. burmanica_ to show the
     elevated oscula (nat. size).

  [Illustration: Freshwater Sponges.                    Plate II.
  Photo by A. Chowdhary.     Spongilla, Tubella, Corvospongilla.]




  PLATE III.

  PHOTOGRAPHS OF SPECIMENS OF _Plumatella_, _Lophopodella_, AND
  _Pectinatella_.

  Fig. 1. Specimen in spirit of _P. fruticosa_ (typical
     form) on the leaf of a bulrush from a pond in the Calcutta
     Zoological Gardens (nat. size).

  Fig. 2. A small zoarium of the _benedeni_ phase of _P.
     emarginata_ from Rangoon (nat. size). Part of the mass has
     been removed at one end to show the structure. The specimen
     was preserved in spirit.

  Fig. 3. Part of a large zoarium of _P. diffusa_ on a log
     of wood from Gangtok, Sikhim (nat. size). An enlarged figure
     of another part of the same specimen is given in fig. 2, Pl.
     IV. The specimen was preserved in spirit.

  Figs. 4, 4 _a_. Specimens of _L. carteri_ from Igatpuri
     Lake, Bombay, preserved in formalin. Fig. 4 represents a
     mass of polyparia surrounded by a green gelatinous alga on
     the stem of a water-plant; fig. 4_a_ an isolated polyparium
     with the polypides fully expanded from the under surface of
     a stone in the same lake. Both figures are of natural size.

  Fig. 5. Part of a compound colony of _P. burmanica_ on
     the stem of a reed from the Sur Lake, Orissa (nat. size,
     preserved in formalin).

  [Illustration: Phylactolaematous Polyzoa.            Plate III.
  Photo by A. Chowdhary. Plumatella, Lophopodella, Pectinatella.]




  PLATE IV.

  SPECIMENS OF _Plumatella_.

  Fig. 1. Vertical branch of a polyparium of _P. emarginata_
     from Calcutta, to show method of branching (× 8). The
     specimen was preserved in formalin, stained with hæmalum,
     and after dehydration and clearing, mounted in canada
     balsam.

  Fig. 1 _a._ Part of a young, horizontal zoarium of _P.
     emarginata_ from Rangoon (× 4, preserved in spirit).

  Fig. 2. Part of a zoarium of _P. diffusa_ from Gangtok,
     Sikhim (× 4). See Pl. III, fig. 3.

  Figs. 3, 3 _a._ Specimens in spirit of _P. allmani_ from
     Bhim Tal (lake), W. Himalayas. Fig. 3 represents a mature
     polyparium; fig. 3 _a_ a young polyparium to which the
     valves of the statoblast (×) whence it had arisen are still
     attached.

  Fig. 4. Part of a zoarium of the _coralloides_ phase of _P.
     fruticosa_ (from Calcutta) preserved in spirit, as seen on
     the surface of the sponge in which it is embedded (× 3).

  Fig. 5. Part of the margin of a living polyparium of _P.
     punctata_ from Calcutta (× 8) with the polypides fully
     expanded.

  [Illustration: Phylactolaematous Polyzoa.             Plate IV.
  A. C. Chowdhary, del.                              PLUMATELLA.]




  PLATE V.

  SPECIMENS OF _Plumatella_, _Stolella_, AND _Pectinatella_.

  Fig. 1. Part of a zoarium of the _coralloides_ phase of _P.
     fruticosa_ (× 10) from Calcutta. The specimen, which was
     preserved in spirit, had been removed from a sponge of
     _Spongilla carteri_.

  Fig. 2. Terminal branch of a polyparium of _P. punctata_
     from Calcutta (× 30). The specimen was preserved in
     formalin, stained with hæmatoxylin, and finally mounted in
     canada balsam.

  Fig. 3. Part of an adult polyparium of _S. indica_ from
     the United Provinces (× 30). The specimen was preserved in
     formalin, stained with hæmalum, and finally mounted in
     canada balsam. The lower zooecium contains a mature free
     statoblast, the upper one a fixed one.

  Fig. 4. The growing point of a young polyparium of the
     same species from Calcutta (× 30), to show the method of
     formation of the stolon that connects the different groups
     of zooecia. The specimen had been treated in the same way as
     that represented in fig. 3.

  Figs. 5, 5 _a_. Zoaria from a compound colony of _P.
     burmanica_ from the Sur Lake, Orissa (× 2). The specimens,
     which were preserved in formalin, are represented as seen
     from the adherent surface of the colony.

  [Illustration: Phylactolaematous Polyzoa.              Plate V.
  A. C. Chowdhary, del.      Plumatella, Stolella, Pectinatella.]




       *     *     *     *     *




Transcriber's note:

  In the Systematic Index, sub-family items were renumbered from 15.
    through 38., to correspond to the numbers used in the text of the
    book.
  Greek letters used as symbols are spelled out, e.g. alpha, beta, etc.
  Letters missing or mis-typeset were inserted, e.g. 'practica ly' to
    'practically'
  Footnotes were moved after the paragraph to which they pertain.
  Raised dots were replaced with decimal points in numeric notations.
  Bold page numbers in the index are surrounded by tildes, e.g. ~76~.
  Punctuation was standardized.
  Added a description of a sketch contained within one line of text.

  Other changes:
    'recognzied' to 'recognized' ... be recognized....
    'benegalensis' to 'bengalensis' ... lacustris var. bengalensis,...
    'pecular' to 'peculiar' ... the peculiar amphipod ...
    'milar' to 'similar' ... similar in the two ...
    'large' to 'larger' ... a little larger than the upper ...
    'pennsylvania' to 'pennsylvanica' ...Tubella pennsylvanica...
    'variely' to 'variety' ... specimens of the variety ...
    'measurments' to 'measurements' ... the average measurements ...
    'It' to 'Its' ... Its buds, however, possessed ...
    'dispsition' to 'disposition' ... 'Y-shaped disposition of ...
    'Wood's Holl' to 'Wood's Hole' ... Biol. Bull. Wood's Hole,...
    '1852' to '1851' at the end of the citation of Leidy's paper, to
       match date at the beginning of the citation paragraph.
    'syoecium' to 'synoecium' ...in a gelatinous synoecium...
    'Lacustre' to lower case ...Ann. Biol. lacustre,...
    'Dactyloccopsis' to 'Dactylococcopsis' ... Dactylococcopsis
       pectinatellophila ...
    'amphioxus' to 'amphioxous' ... amphistrongylous or amphioxous ...
    'Trìda' and 'Trida' to 'Trída' for consistency ... Praze, Trída ...