IC)I5-] Fauna of the Chilka Lake : Coelenterates. 79 



tendency to be arranged in groups, but these groups are never pedicellate. In a state 

 of extreme contraction the individual tentacles may become knob-like, but they are 

 always elongate and very slender when fully expanded. 



The walls of the column are either smooth or covered with minute solid tubercles 

 produced by swellings of the mesogloea. The cinclides, which are scattered on the 

 upper part of the column, are conspicuous in the living animal but difficult to detect 

 in preserved specimens. The central part of the column is often encased in a loose 

 sheath of mucus and extraneous particles. 



The number of mesenteries is never great. The normal number is 12 complete 

 and 12 incomplete; the latter are almost vestigial, lacking muscle-banners, filaments 

 and gonads. All the complete mesenteries are normally fertile and the species 

 appear to be dioecious. Owing to the presence of large mesenterial stomata 

 (which vary greatly in size, shape and position but are as a rule internal), transverse 

 sections through the stomodaeal region frequently show gaps in the membrane of the 

 complete mesenteries. It is possible, however, that the stomata are capable of 

 almost incomplete obliteration by contraction. 



So far as can be judged from published figures, 1 the species of Phytocoetes bear 

 a remarkable if superficial resemblance to the aberrant genus Scytofthorus, but they 

 have no morphological relationship to that genus and have probably been derived, 

 as I have already indicated, from Metridium in an environment in which solid ob- 

 jects of attachment are scarce and the bottom is almost uniformly soft and muddy. 



The type-species of Phytocoetes is P. gangeticus, sp. nov. 



The genus is only known from brackish water and water of variable salinity on 

 the east coast of India. 



Phytocoetes gangeticus, sp. nov. 



(Plate viia, figs. 3, 3a, 3Ô.) 



1907. Metridium schillerianum var. exul (in part), Annandale, Rec. Ind. Mus. 

 I, p. 48, pi. iv. 



The animal is colourless in spirit ; in life it may be described as being of a pale, 

 translucent greenish flesh-colour. When the tentacles are retracted the uppermost 

 visible part of the column is tinted with olivaceous green, but the retractile region 

 immediately below the oral disk is pale. The tentacles are greenish or yellowish, 

 with a pale purplish tinge due to the presence of algae in the cells of the endoderm ; 

 they bear no definite markings. When the column is fully expanded the bodv- 

 wall is remarkably transparent, especially in the anterior parts. 



The column is protean in form, sometimes contracted into a subspherical or 

 barrel-shaped mass, sometimes elongate and almost cylindrical and at least four times 

 as long as wide ; in either condition it is frequently divided transversely by clear-cut 

 circular constrictions. Sometimes the aboral region is fully extended and very nar- 

 row, while the anterior parts are contracted and broad; often the converse is the 



1 Hertwig. " Challenger" Rep. Zool., VI (I), Actiniaria, p. 104, pi. iii, fig. 6 (1882). 



