No. 567] EFFECT OF DISTRIBUTION ON SPECIATION 143 



TABLE VIII 

 Speciation op Birds in Various Pai 

 from Eartert (1912), Dresser (190', 

 Stejneger (1885) 



Ogawa (1908) and 



Stejneger (1885). The increase in index of modification 

 from Ireland to the British Isles, and then to the entire 

 Palaearctie region, is almost exactly what should be ex- 

 pected. The greater number of both genera and species 

 in Japan as compared with Kamtschatka reflects the 

 greater variety of ecologic niches in a warm country as 

 compared with a cold one of comparable size. A com- 

 parison of the resident species of Japan with the resident 

 species of the British Isles would be of very great inter- 

 est, but such a list of Japanese birds is not available. The 

 very striking similarity between the speciation of birds in 

 Kamtschatka, and that in the British Isles, both in num- 

 ber of genera and of species, is very remarkable. The 

 interesting manner in which the balance of nature is pre- 

 served is shown by the large representation of raptorial 

 birds to parallel the abundance of shore birds and Anseres. 



That reptiles and amphibians are influenced in their 

 speciation by their distribution is indicated by Table IX, 

 which shows a comparison of the genera and species of 

 amphibians, lizards, and snakes, in three of the geo- 

 graphic areas defined by Cope (1898). 



