72 The Hydra of the Calcutta Tanks. [ March, 1905. 
6. The Hydra of the Calcutta Tanks—By Netson ANNANDALE, 
B.A., Deputy Superintendent of the Indian Musewn. 
Description.—Body and tentacles very elongate, the latter not 
clubbed; body cylindrical throughout ; six (sometimes five) tentacles 
in well-grown, five in young, individuals ; ovaries one or two, testes 
numerous. Testes and ovaries do not occur together on the same 
individual. Coloration—Tentacles and base milky white; distal 
portion of the body either pale or dark olive-green, deep chestnut, 
orange-brown, pale brown, cream-colour or dirty white; never 
bright green. 
When I exhibited specimens of the Calcutta Polyp to the 
Society I was inclined to regard it at most as a variety of Hydra 
viridis, using the specific name in a more extended sense than 
its author Linneus adopted, to include H. fusca. A careful 
study of the descriptions of the European forms and an examina- 
tion of a larger number of Indian specimens has since led me to doubt 
whether I was correct ; in coming to a decision I am indebted to a 
note received from my friend Dr. J. H. Ashworth, of the University 
of Edinburgh, who has not, however, seen the Indian form. On the 
whole this form appears to be related to Pallas’ H. vulgaris ; but 
the question of specific characters, in animals so simple and so 
variable in appearance from moment to moment, is a very difficult 
one. From typical specimens of H. vulgaris! it differs im several 
important details. 
When the animal is clinging to an inclined or vertical surface 
the expanded tentacles are arched, their proximal portion project- 
ing in a straight line from the disk, while the distal extremity 
either falls downwards or extends upwards. Every phase of 
colour may be found in the same tank, but the darker speci- 
men are more common over deeper water. Specimens kept in a 
bright light fade so as to become of an almost pure and uniform 
white, whatever their original coloration may have been. 
The Polyp is usually found on the under surface of the 
floating leaves of water-plants. It is by no means uncommon 
but may be a little hard to find. Sexual reproduction takes 
place at any rate from December to March, but probably 
1 T have just seen Downing’s recently published summary of what is 
known regarding the species of Hydra, in his paper on “‘ The Spermatogenesis of 
Hydra. (Zool. Jahrb., Anat.,1905.) He recognizes, on what appear to be suffi- 
cient grounds, the following four, with one variety of the first :—(1) H. viridis, 
Linn.; (2) H. grisea, Linn. (with H. vulgaris, Pall.,as a synonym); (8) H. 
fusca, Linn.; and (4) H. diwcia, Downing. If sexual characters are to be 
taken into account, as has been done in constituting H. diwcia—and the only 
objection is that a specimen which it is desirable to identify may not be breed- 
ing—then the Indian Hydra should be regarded as a distinct species, though 
it may only be protandrous or the converse. Under the circumstances it 
will be convenient to give it, at any rate provisionally, specific rank, calling it 
4H. orientalis. The description above is a sufficient diagnosis. June 6th, 1905. 
