MADREPORARIAN CORALS 89 



in general form, in the size of the cahces, and in other char- 

 acters which are available for the determination of species, 

 that the task of the conscientious systematist seems to be 

 a hopeless one. No attempt can be made in these pages to 

 help him. 



But there is one consideration of this problem which is 

 worth bearing in mind, and may be of more general interest. 

 If we consider a large collection of specimens of a Madrepora 

 from a given reef, we may regard the differences we observe 

 between them to be due either to characters inherited by 

 them from their parents or to the moulding and fashioning 

 effects of external forces that have played upon them from 

 the time when the ciliated larvae from which they have 

 sprung first settled down upon a rock. 



If it were possible for us to experiment by breeding 

 Madrepores, as we breed mice or canaries, we could determine 

 whether these differences are inherited or not. But at 

 present the difficulties in the way of making pure cultures 

 of these corals seem to be insuperable. 



In the absence of such direct experimental evidence, 

 which can alone decide the matter, it is open to us to hold 

 the opinion that the variations are due to local environ- 

 mental conditions, and on this assumption we may hold 

 that in such a genus there has been no subdivision into a 

 large number of distinct specific groups, but only one large 

 and very variable species is represented. 



This view has not been proved to be correct or incorrect, 

 but if it is correct, then we have a species which shows 

 extraordinary powers of adapting itself in various ways to 

 the complex of local conditions, and it may be that this 

 adaptability or plasticity, as it is sometimes called, is an 

 important character in gaining for the species its predomi- 

 nance on the reefs. 



The word madrepore ^ was first used by Imperato in 1599, 

 and there can be little doubt that the coral which he called 

 Madrepore was the Mediterranean coral now called Dendro- 



1 The word madrepore has been frequently translated " Mother stone " 

 {Porus )natronalis), but should be translated " JMother of stone." Cf. Ital. 

 Madreperla = Mother of pearl. 



