112 



Memoirs of the Indian Museum. 



[Vol. V, 



hydranth. The bushy masses of the more robust phase may, on the other hand, 

 reach a length of 20 cm. In both phases the stems are single and even when the 

 colony is most luxuriant they never become agglutinated or even intertwined, its 

 luxuriance being due solely to the profuse production of stems from the rhizome and 

 their still more profuse branching in one plane. Even the largest masses are soft 

 and lax, for the stems and branches are not thickened, and it is only when the former 

 are very short that they are at all stiff. 



The chitinous investment of the hydrophyton, though not hard, is thick and 

 brown. It extends up the stalks of the hydranths, round the base of the latter and 

 for a short distance up the tentacles, on which, however, it is thin and almost colour- 

 less. Consequently the exact point it reaches can be detected with difficulty. When 

 the hydranths are contracted the thin investment of their bases is to some extent 

 invaginated into the thicker and stiffer covering of the stalk (pi. ix, fig. 3). 



The hydranths are spindle-shaped and fairly slender when fully extended, their 

 tentacles are capable of great elongation. As a rule the tentacles, which are borne 



in two alternating circles, are 8 or 10 in number. 



The base of the stems and lateral branches 

 is always annulated for a short distance, but the 

 annulation is often very obscure. So far as I can 

 see it is never spiral. This is also the case with 

 the stalks of the gonophores, which (the stalks) 

 are always shorter than the gonothecae. 



These thecae are borne at the base of the 

 considerably longer stalks of the hydranths. 

 When immature they are almost spherical and 

 when mature vary considerably in size and out- 

 line. Generally speaking, those of the female 

 gonophores tend to become c}dindrical as the 

 ovum ripens, whereas those of the male gono- 

 phores assume an ovoid form with the growth of the gonad and become almost 

 pointed distally. There is usually a small pimple-like projection at the extreme 

 tip, especially in mature male gonothecae (fig. 10). 



Traces of the circular canals persist at the base of the gonophores but are 

 not well developed. In both sexes the spadix is a simple cylindrical or somewhat 

 spindle-shaped body. In the female gonophore, which produces a single egg, the 

 spadix extends up one side of the egg and arches over it slightly. The distal ex- 

 tremity is slightly emarginated outwardly, so that the spadix has precisely the shape 

 of the human finger (pi ix, fig. 3a). In this sex it is of an orange or brownish colour. 

 The ovum and the young planula are usually white but, at any rate in the bushy 

 form of the species, sometimes have a bluish tinge. The spadix of the male gonophore 

 is symmetrical and somewhat less curved; it extends up the interior of the 

 gonophore nearly to the tip of the latter and is invisible externally in the living 

 animal. 



Fig. 10. — Bimeria fluminalis, sp. nov. 

 Male gonophore, from a stained speci- 

 men. 



