OYSTERS OF THE CHALK, 

 AND THE THEORY OF DEVELOPMENT 1 . 



THE interesting notice in your last number, of M. 

 Coquand's ' Oysters of the Chalk/ draws inferences 

 unfavourable to the theory of development or evolution 

 which scarcely seem warranted by the facts. It need 

 not be ' difficult to imagine the creature as existing 

 under such conditions, that one species, while engaged 

 in ' ' the struggle for existence/' should starve out and 

 extinguish another/ for however widely we may find 

 a fossil species dispersed, it is not probable that it 

 occupied the whole of its territory at one and the same 

 time, and in the limited area occupied immediately 

 before its extinction, new varieties may have prevailed 

 over and displaced the old by some slightly superior adap- 

 tation to the food-supply of the region. The extinction 

 of any particular species may in some instances have 

 been due to the extinction, or loss by other means, of its 

 own appropriate food. Again, it is not necessary to 

 suppose that the hinge, or the internal or external 

 structure of the shell of an oyster, has been altered by 



1 Reprinted from 'Nature,' No. 30. 



