Similarity of Adaptations in Different S pecies 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.*** 
156Cope: 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. 159—163, 164—165, 175—176, 
182—183, 20I—203, 273. 
