78 Memoirs of the Indian Museum. [Vol. V, 



Metridium schillerianum has recently been found in great abundance on posts 

 and bridge-piers in canals and creeks of brackish water on the outskirts of Calcutta. 

 In such positions it is often surrounded by sponge- like masses formed of the tubes of 

 a small Sabellariid worm that builds in mud. On one occasion the water under a 

 bridge on the piers of which the anemone occurred had a specific gravity of only 

 i' 006, but individuals from this bridge lived for less than three days in pure fresh 

 water, whereas others placed in water of a much higher salinity flourished. 



The species has as yet been found only in brackish water in the Gangetic delta :— 

 at Port Canning on the Mutlah river, in canals and creeks connected with the same 

 system near Calcutta, and in the Hughli at Diamond Harbour. It does not occur in 

 the Chilka Lake, in which suitable conditions are very rarely to be found. Mr. T. 

 Southwell, however, recently took a specimen on a muddy bottom near the edge 

 of the river at Diamond Harbour. 1 



Genus Phytocoetes, nov. 



The genus may be defined concisely as follows: — 



Thin-walled Metridiinae without a collar, with the column capable of 

 considerable elongation but protean in form, with the basal disk small and 

 unmuscular, never strongly adhesive, with the aboral region capable of 

 assuming a physa-like shape and appearance, with retractile tentacles 

 arranged round the margin of an undivided and non-lobulate oral disk ; 

 the tentacles thread-like when fully expanded but highly contractile. 



In both the species assigned to this genus the body-wall is very thin in a state of 

 expansion, but can be considerably thickened at any point by the contraction of the 

 circular muscle. This muscle lies on the mesogloea at the base of the endoderm, 

 upon which it does not encroach ; it forms a continuous sheath over the whole of the 

 column, but, though uninterrupted anatomically, can be differentiated physiologically 

 into numerous transverse strands almost visible to the naked eye and capable of 

 independent contraction and expansion. When the animal is floating in the water or 

 supported amidst filamentous algae or other similar plants the anterior region of the 

 column is as a rule somewhat narrower than the aboral part, which may be swollen 

 and bladder-like; but when it is at rest in mud, on roots or in sponges, the latter 

 region is strongly contracted and cylindrical while the anterior part is more or less 

 barrel-shaped (pi. vii, fig. 2). In all stages of expansion the basal disk is distinct. 

 If the animal be subjected to abnormal or unhealthy conditions the column may 

 assume almost any form, for the thin muscular walls permit constant and almost 

 instantaneous changes of shape. In one species there is a distinct mesogloeal 

 sphincter, in the other it is absent. The contractions and expansions of the circular 

 muscles cause very great changes in the microscopic appearance of the column-wall. 



The tentacles are never very numerous ; in one species the normal number is 

 from 48 to 60, in the other 24. In the living animal they sometimes exhibit a 



1 Cf. Gosse on Sagartia troglodytes in Actin. Brit., p. 95 (i860). 



