94 THE TRIUMPH OF THE MAMMALS 



how it was evolved. The reptiles' scales did not 

 evolve into hair, as those of the ancestor of the bird 

 were transfomred into feathers. Probably the hair 

 grew up out of the skin underneath the scales, and 

 eventually made the scales superfluous. When one 

 of the lower (not the lowest) mammals is developing 

 in the womb, and the hair begins to appear, it grows 

 in tufts or patches, as if each had originally grown 

 under a scale. 



You notice that in this case I look for guidance 

 to one of the lower, but not lowest, mammals, and 

 this may surprise you. The fact is that the lowest 

 mammal in nature to-day — you will be introduced to 

 it in a moment — has no womb in which it bears its 

 young. It lays eggs, as snakes or turtles do. And 

 this throws a very interesting light on the evolution 

 of the third and greatest feature of our mammal 

 family, the nourishing of the young. 



As we saw, the mothers which would carry on their 

 species through the stress of the Ice Age must, if they 

 lived in the temperate regions, care for their young. 

 The bird continued to lay eggs, but, unlike the reptile, 

 provided warmth for them with its own body. An 

 alternative way would be to hatch the eggs inside the 

 mother's body, and this line the mammals have fol- 

 lowed. Every animal that is bom comes of an Qgg\ 

 though, to use a colloquialism, "there are eggs and 

 eggs." At first, however, the ancestor of the mammals 

 continued to lay eggs, like its reptile foremothers — I 



