EVIDENCES OF EVOLUTION 19 



the same species, like James and Jervis, or 

 Hood and Gardner. The faunas of the 

 larger central islands are again more closely 

 related to each other than are the faunas of 

 the more isolated islands like Tower, Bindloe, 

 Abingdon, Hood and Charles. The tortoise 

 of Duncan is closest to the tortoise from Ab- 

 ingdon; at the same time the Tropidurus of 

 Duncan comes nearest to that of Abingdon. 

 The prevention of intercrossing after the 

 separation of the islands, the time of separa- 

 tion, and the difference in the conditions on 

 the different islands, are the factors which 

 produce the different races.' 3 



We may also refer the student to Wallace's 

 fascinating "Island Life' : for further illus- 

 trations of the evolutionary suggestiveness of 

 the exploration of islands. 



OTHER GEOGRAPHICAL EVIDENCES. As in 

 other parts of this little book we have dwelt 

 on one interesting illustration of a large 

 subject, we cannot do more than refer briefly 

 to some of the other geographical evidences. 



With the help of the palaeontologist it is 

 sometimes possible to come to a conclusion as 

 to the original headquarters of a particular 

 race of plants or animals, and then it is found 

 that the present-day distribution of the 

 members of the race is readily intelligible on 

 the evolutionary assumption of diffusion from 



