Freshwater Sponges, Hydroids & Polyzoa

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 1a. reticulata, Annandale 71, 241 2. proliferens, Annandale 72 3. alba, Carter 76 3a. cerebellata, Bowerbank 76 3b. 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 8a. mollis, Annandale 88 8b. cava, Annandale 88 9. fragilis, Leidy 95 9a. calcuttana, Annandale 96 9b. decipiens, Weber 97 10. gemina, Annandale 97 11. crassissima, Annandale 98 11a. crassior, Annandale 98 1C. Stratospongilla, Annandale 100 12. indica, Annandale 100 13. bombayensis, Carter 102, 241 13a. 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 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.

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.

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