120 



THE GENESIS OF SPECIES. 



[ClIAP^ 



that tliL' remains were preserved of the Ichthyosauri and 

 riesiosauri, which appear to have represented the Cetacea 

 during the secondary geological period. 



SKELETON OF A PLESIOSAURUS. 



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 wliich are atrophied and reduced in numlier, as 

 compared with those of most other Vertebrates. Now, if 

 the winiT 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 



, ,-^^\^:^^^^«*?^WW^A^\A•^•^•^--,,. 



"^ksmmiiimm. 





SKELETON OF AN ICHTHYOSAURUS. 



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

 gence from the ordinary vertebrate tin-liml). In the 

 ichthyosaurus, in the plesiosaurus, in tlie 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 tlieir joints, which are, on the contrary, multi- 

 plied in Cetacea and the ichthyosaurus. And even in the 



