Evolution 



and a tail are possessed in common by the embryos of all higher 

 animals, only afterwards to disappear in those types in which 

 the adult animal is without these structures. The heart of the 

 mammal or bird is at first simple, then two chambered like that 

 of a fish, then three chambered like an amphibian's, and finally 

 four chambered. Some of the main phases in the development 

 of the rabbit and of man are shown in Figs. 14 and 15 respec- 

 tively. 



The young flat-fish is like an ordinary member of the fish 

 tribe, with an eye on either side of its head, and its body built on 

 the ordinary symmetrical lines. It is only later, when it begins 

 habitually to lie upon one side on the sea bottom, that the eye 

 from the under side wanders round to the opposite aspect beside 

 its fellow, and the upper side becomes pigmented, while the 

 lower remains white. 



In similar fashion a primitive form of kidney is, as it were, 

 sketched in, in the development of the higher animals, only to 

 be erased at a later stage and replaced by a better form. The 

 human child has a complete body covering of hair, which dis- 

 appears soon after birth. In these and many more instances, 

 one cannot avoid the impression that the organism has not been 

 specially designed for what it finally comes to be. It cannot 

 forget, and must needs repeat, or so it seems, some considerable 

 part of the history of its race. 



Manifestly, then, all this evidence, gleaned from many 

 different sources, points to a common origin of living things, 

 and to the gradual evolution of the higher from the lower types. 

 It may also be said that there is no scientific evidence against 

 such a view. 



22 



