igoy.] Records of the Indian Museum. 73 



Granted that Metridium schillerianum var. exul is an isolated 

 race of the species to which I have referred it, it still remains to be 

 discussed whether this race has become differentiated in the ponds 

 at Port Canning, and how long the process of its evolution has 

 taken to reach the present stage. The historical evidence on these 

 points, although it cannot be called absolutely conclusive, is 

 much stronger than such evidence usually is. Stoliczka's account 

 of the typical form of the species was written in 1868 (at which 

 date the extent and number of the ponds were probably not the 

 same as they are today) and was more detailed than any dealing 

 with the Sagartiidse which had previously appeared, although it 

 contained a number of misconceptions rather than errors of obser- 

 vation. Its author was a trained and cautious observer and appa- 

 rently examined the ponds at more than one time of year. It is 

 improbable that he only did so on occasions when the water had 

 been rendered turbid by rain. Except under these conditions he 

 could not have failed to see the Actinians, had they occurred in 

 the ponds ; nowadays they are the most characteristic feature of 

 the fauna to which they belong, and strike even a casual observer. 

 Native fishermen at Port Canning volunteered the information, 

 when I asked them about the fish in the ponds, that there was in 

 the mud " an animal just like a flower." It is unfortunate that we 

 do not know in which of the ponds StoHczka found the Actinian, but 

 I suspect that it was the one nearest to the railway station. Its 

 usage for domestic purposes has now rendered the water of this 

 pond foul. Stoliczka said that the Actinian did not live in the 

 other ponds at Port Canning because they did not contain logs 

 of wood, and because their water was unsuitable. The last state- 

 ment is not explained. The logs of wood no longer exist, and their 

 place has not been taken by other solid substances to which the 

 animals might have attached themselves. It has been shown that 

 the race of the Actinian now found in the ponds does not attach 

 itself to fixed bodies, but has become adapted for a burrowing life. 

 So far as the neighbourhood of Port Canning is concerned, I feel 

 sure that this new race is only to be found in the ponds ; but our 

 ignorance of the Actiniarian fauna of the Indian seas makes it 

 impossible to deny that an identical form may occur elsewhere. 

 Even should this prove to be the case, however, it would not 

 necessarily be uncritical to argue that similar causes have produced 

 convergence among the offspring of different individuals. 



However, it is perhaps better not to introduce questions of pos- 

 sibility ; my object in this paper has been to give an unbiassed 

 account of the differences and resemblances between two Actinians 

 which I take to be no more than races of a single species. One of 

 these races has been isolated in certain small ponds, in which it 

 appears to have responded to its environment to such an extent 

 as to have altered very considerably both its structure and its mode 

 of life. 



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