128 THE AMERICAN MUSEUM JOURNAL 
prove that the divergent types of neighboring or distant valleys have 
arisen from common ancestors and that they have changed little by 
little, in one place and another, so as to become the distinct and character- 
istic types of their own neighborhoods. The evidence proves also that 
the snails have evolved primarily by “sporting,” or mutation in the 
de Vries sense, and that the internal or constitutional factors are the 
potent ones, for the geological, climatic and general biological conditions 
are more uniform in these islands than anywhere else in the world. ‘The 
Ben es agen ae A 

MANGAIA, ONE OF THE COOK ISLANDS 
An uplifted coral limestone island 
assignment of a secondary importance to environment is one of the princi- 
pal results of iny investigation. 
A second result of equal importance is even more interesting. It is 
that the evolution of new types is taking place at the present time, as the 
evidence amply demonstrates in several instances discovered in different 
islands. My investigations give long-desired proof that the differentia- 
tion of species is going on under surroundings that are entirely natural 
