120 



THE GENESIS OF SPECIES. 



[CHAP, 



that the remains were preserved of the Ichthyosauri and 

 Plesiosauri, which appear to have represented the Cetacea 

 during the secondary geological period. 



SKELETON OP A PLESIOSAUKUS. 



As another example let us consider the origin of wings, as 

 they exist in birds. Here we find in fact an arm, the bones of 

 the hand of which are atrophied and reduced in number, as 

 compared with those of most other Vertebrates. Now, if 

 the wing took its origin from a terrestrial or subaerial 

 organ, this abortion of the bones could hardly have been 

 serviceable hardly have preserved individuals in the 

 struggle for life. If it arose from an aquatic organ, like 



SKELETON OP AN ICHTHYOSAURUS. 



the wirjg of the penguin, we have then a singular diver- 

 gence from the ordinary vertebrate fin-limb. In the 

 ichthyosaurus, in the plesiosaurus, in the whales, in the 

 porpoises, in the seals, and in others, we have shortening 

 of the bones, but no reduction in the number either of the 

 fingers or of their joints, which are, on the contrary, multi- 

 plied in Cetacea and the ichthyosaurus. And even in the 



