Similarity of Adaptations in Different Species 205 



for it would lead us back to the question which Spencer 

 has raised with his example of the more acute sense of 

 taste in the papillae of the tongue, and of which we have 

 spoken above. But apart from that, is it possible for 

 this argument, however unassailable it may be from a 

 purely logical point of view, really to weaken the strong 

 presumption in favor of transmissibility which is derived 

 from the fact that inborn structural relations always 

 follow though slowly and tardily those acquired in 

 life through functional adaptation, as the shadow follows 

 the body? 



Another fact among those which speak most con- 

 vincingly in favor of the inheritance of acquired char- 

 acters is the similarity of certain structures in different 

 species which are subjected to the action of the same 

 mechanical conditions. Without needing to bring up 

 the most typical and most familiar case, viz., the trans- 

 formation of the extremities of the whale into fins, it 

 would be enough to recall as examples the like char- 

 acter of the leg joints in the two-hoofed animals 

 (Diplartha, Cope) and the rodents, which is attributed 

 to their rapid locomotion; the like structure of the 

 extremity of the radius in the edentates and the quadru- 

 mana which possess the power of supinating the hand; 

 the like reduction in number of the digits in many 

 orders of digitigrade mammals which run about on the 

 dry hard ground; the like modifications in the form and 

 development of crests on the skull following like employ- 

 ment of the canine teeth as fighting teeth in all orders 

 in which these teeth are strongly developed. 156 



158 Cope : The mechanical Causes of the Development of the hard 

 Parts of the Mammalia. Journal of Morphology, vol. VIII, No. 2. 

 Boston, U. S. A., Ginn, Sept. 1899. P. 159163, 164165, 175176, 

 182183, 201203, 273. 



