254 THE THEORIES OF EVOLUTION 



use or disuse of organs and some to the motions ani- 

 mals perform in response to external stimuli. This is 

 what Cope calls kinetogenesis. 



Kinetogenesis claims Cope's special attention and 

 this is in perfect accord with the Lamarckian view- 

 point. Cope deserves much credit for not confining 

 himself to a theoretical discussion but bringing forth 

 much evidence in support of his thesis. His evidence 

 was derived partly from the observation of the lower 

 animals such as muscular tissue which he regards as 

 having developed in higher Protozoa at the expense 

 of the protoplasmic filaments which are observable in 

 the lower Protozoa; plication of the columella in 

 gastropods, resulting from the insertion and activity 

 of the muscles, etc. But it is in the vertebrates, and 

 especially the vertebrate skeleton, that Cope, thanks 

 to his marvellous knowledge of paleontology, finds 

 most of his evidence. 



"In the first place, I will select an illustration of 

 the effects of use on the articulations of the limbs and 

 feet of the Mammalia. I take first the ankle and 

 wrist- joints. In the ruminating animals (ox, deer, 

 camel, etc.) and in the horse, among other living spe- 

 cies, the ankle-joint is a very strong one, and yet ad- 

 mits of an extensive bending of the foot on the leg. 

 It is a treble tongue-and-groove joint; that is, two 

 keels of the first bone of the foot, the astragalus, fit 

 into two grooves of the lower bone of the leg, the tibia, 



