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



evidently adapted in structure for life in different phases of the same environment. 

 The peculiarities of M. schillerianum are mainly physiological; to these are added, in 

 the case of Pelocoetes and Phytocoetes , special structural characters. 



In 1907 (op. cit.) I expressed the opinion, somewhat tentatively, that the type 

 now called Pelocoetes was a variety, local race, or possibly an unfixed phase of 

 Metridium schillerianum produced by isolation, and that the form here recognized as 

 a distinct genus under the name Phytocoetes was merely the young of Pelocoetes. 

 This view ignored, perhaps rightly, the fact that many individuals of the Phytocoetes 

 type are sexually mature. In any case it is rendered untenable in its entirety by the 

 discovery in the Chilka Lake of anemones of both the Pelocoetes and the Phytocoetes 

 types. Stress must be laid, nevertheless, on the resemblance between the latter 

 type and the young of the Sagartiidae. In Sagartia troglodytes 1 the young, at any 

 rate in some cases, is born as a small actinian differing from its parents mainly in the 

 smaller number of its tentacles and mesenteries, in the poorly developed condition 

 of its basal disk, in the tendency displayed by its column to assume at one time a 

 spherical or subspherical, at another an elongated shape, and in its much more mobile 

 habits. These are precisely the differences between Phytocoetes and Metridium. 

 Some years ago I obtained the young of M. schillerianum from individuals taken 

 from a post in the Mutlah estuary, and kept them in an aquarium full of water from 

 one of the brackish pools at Port Canning. The adults of this species are almost 

 invariably found in hollows on a rough surface (e.g. in the empty shells of Balanus or 

 among masses of worm-tubes), but the walls and bottom of my aquarium were quite 

 smooth. The young anemones closely resembled those of S. troglodytes and were 

 apparently devoid of a columnar collar ; they lived for some months and increased 

 considerably in size, without losing their juvenile form. Unfortunately, during 

 my absence from India, the aquarium was allowed to dry up and they perished 

 before a detailed examination could be made. All that can be said about them 

 therefore is that they continued for some months to resemble both Phytocoetes and 

 the young of Sargartia in outward appearance. 



The species of Phytocoetes found in the Chilka Lake is distinct from that origin- 

 ally obtained at Port Canning and since taken in the immediate neighbourhood of 

 Calcutta. I have given the latter the name of P. gangeticus and the former that of 

 P. chilkaeus. 



Although on taxonomic grounds I now propose to regard Phytocoetes as distinct 

 generically from Metridium, the facts of the case, regarded from a biological point 

 of view, seem to point to the probability of the former being no more than a perma- 

 nent or quasi-permanent larval (or rather post-larval) phase of the latter. In other 

 words, it seems likely that Phytocoetes gangeticus bears to Metridium schillerianum 

 much the same relationship as the axolotl does to Ambly stoma tigrinum. P. chil- 

 kaeus may either be related in the same way to an unknown species of Metridium 

 or be a direct descendant of either M. schillerianum or P. gangeticus in which evolu- 



Ashworth and Annandale, Proc. Roy. Soc, Edinburgh, XXXV, p. 4 (1904). 



