84 EVIDENCES OF EVOLUTION. 



geographical distribution, or the history of the diffusion of 

 animals from centres where the presumed ancestral forms 

 are or were most at home, favour the doctrine of 

 descent. 



The individual life history of an animal — often strangely 

 circuitous or indirect — is interpretable as a modified re- 

 capitulation of the probable history of the race. The 

 embryo mammal is at one stage somewhat like an embry- 

 onic fish, at another like an embryonic reptile ; even in 

 details, the recapitulation, if such we may term it, is some- 

 times faithful. 



Such, in merest outline, is the nature of the evidence 

 which leads us to conclude that the various forms of life 

 have descended or have been evolved from simpler ancestors, 

 and these from still simpler, and so on, back to the mist of 

 life's beginnings. 



In accepting this conclusion naturalists are practically 

 unanimous ; but in regard to the manner in which the 

 modification of species or the general ascent of life has been 

 brought about, there is much difference of opinion. The 

 fact of evolution is admitted ; debate goes on with regard 

 to the factors (see Chap. XXX.). 



