III. 



ON THE THEOEY OF EVOLUTION. 



At a meeting of the Philadelphia Academy of Natural Sci- 

 ences, held February 23, 1876, Prof. Cope gave a history of the 

 progress of the doctrine of evolution of animal and vegetable 

 types. While Darwin has been its prominent advocate within 

 the last few years, it was first presented to the scientific world, in 

 a rational form, by Lamarck, of Paris, at the commencement of 

 the present century. Owing to the adverse influence of Cuvier, 

 the doctrine remained dormant for half a century, and Darwin 

 resuscitated it, making important additions at the same time. 

 Thus Lamarck found the variations of species to be the primary 

 evidence of evolution by descent. Darwin enunciated the law of 

 "natural selection" as a result of the struggle for existence, in 

 accordance with which "the fittest" only survive. This law, 

 now generally accepted, is Darwin's principal contribution to the 

 doctrine. It, however, has a secondary joosition in relation to 

 the origin of variation, which Lamarck saw, but did not account 

 for, and which Darwin has to assume in order to have materials 

 from which a " natural selection " can be made. 



The relations exhibited by fully grown animals and plants 

 with transitional or embryonic stages of other animals and plants, 

 had attracted the attention of anatomists at the time of Lamarck. 

 Some naturalists deduced from this now universally observed 

 phenomenon that the lower types of animals were merely re- 

 pressed conditions of the higher, or, in other words, were embry- 

 onic stages become permanent. But the resemblances do not 

 usually extend to the entire organism, and the parallels are so 

 incomplete that this view of the matter was clearly defective, 

 and did not constitute an explanation. Some embryologists, as 

 Lereboullet and Agassiz, asserted that no argument for a doctrine 

 of descent could be drawn from such facts. 



The speaker, not adopting either view, made a full investiga- 



