54 THE ORIGIN OF MAN 



their own tribe. In the great majority, the limbs 

 were well developed but short and stumpy, and 

 the hind limbs were nearly always longer and 

 heavier, and bore five toes on which the second 

 and third were usually the longest. Another im- 

 portant fact is that in the armor or roof bones 

 and those of the true skull was pierced not only 

 by the lateral orbits in which the paired eyes were 

 situated and by the pair of anterior nasal open- 

 ings, but by also a single small orifice through the 

 bone over the brain, and in it was situated a third 

 eye known as the pineal eye. We have thus seen 

 in all of the vertebrates so far discussed that 

 their habitat is either wholly in the water or at 

 least that the very small eggs are there laid and 

 fertilized externally, and that the 3 r oung are also 

 borne and spend the days of their youth in this 

 element. Of the higher vertebrates they remove 

 themselves more and more from this habitat and 

 none are developed directly from the eggs. The 

 reptiles are oviparous, laying large eggs with a 



