192 Darwin, and after Darwin. 



able throughout their entire length, in the deer, and 

 still more in the camel, their union is more complete, 

 so that they go to constitute a single bone, whose 

 double or compound character is indicated externally 

 only by a slight bifurcation at the base. Nevertheless, 

 if we examine the state of matters in the unborn 

 young of these animals, we find that the two bones 

 in question are still separated throughout their length, 



Fig. 85. — Hipparion. (New World Pliocene.) 



and thus precisely resemble what used to be their 

 permanent condition in some of the now fossil species 

 of hoofed mammalia. 



Turning next from bones of the limb to other parts 

 of the mammalian skeleton, let us briefly consider the 

 evidence of evolution that is here likewise presented by 

 the vertebral column, the skull, and the teeth. 



As regards the vertebral column, if we examine this 



