FOURTH JOURNEY TO THE SOUTH SEAS - 127 
the principles of geographical distribution. Each island possesses its 
own species, while its different valleys have forms that are usually 
markedly different. For instance, in the valley of Tipaerui of Tahiti 
the examples belonging to the species Partula otaheitana are almost all 
twisted to the right, and all of them are rather small, brown and streaked. 
Their relatives in the magnificent valley of Fautaua, a half mile distant, 
are larger, yellower and redder, but the fact of greater interest is that 
the shells of a large proportion of them twist to the left. In Hamuta 

FISHING SCENE IN RAIATEA, SOCIETY ISLANDS 
Distributing the fish caught for a district feast 
Valley, just beyond Fautaua, the right-handed and left-handed members 
of the species are about equal in numbers, while in Pirai Valley beyond 
they are all left-handed. ‘This last valley is the home of a small form, 
Partula filosa, that grows nowhere else in this island, in the group of 
islands or in the world. 
When the collections are sorted out according to species and varieties 
rive ample evidence to 
and according to their geographical source, they gi 
