KINE TOGENESIS. 



297 



A distinct consequence of combined impact and 

 strain is seen in the evolution of the carpus and tarsus 

 of the Diplarthra. In primitive Mammalia, as in 

 most Unguiculata, the 

 bones of the carpus 

 and tarsus succeed 

 each other in such a 

 way that the principal 

 lines of separation be- 

 tween the elements 

 coincide in the two 

 rows, thus producing 

 a linear relation be- 

 tween the former. In 

 the Diplarthra, on the 

 other hand, the ele- 

 ments of the two rows 

 alternate with each 

 other so as to produce 

 a strong interlocking. 

 I have shown that in 

 the primitive Ungu- 

 lata, the Taxeopoda, 

 the linear arrange- 

 ment is observed, 

 while in three orders 

 of ungulates, the Pro- 

 boscidea, Toxodontia, 

 and Amblypoda, there 

 are various degrees of 

 alternation intermediate between the linear type of the 

 Taxeopoda and the completely interlocked condition 

 of the Diplarthra. It has been already pointed out in 

 the chapter on phylogeny that the taxeopodous type 



Fig. 76. Cervus canadensis in motion : 

 from Muybridge's Animal Motion ; showing 

 the " knock-elbow" position of the fore leg, 

 in both plantation and recover. 



