124 THE AMERICAN MUSEUM JOURNAL 
sunilar phenomena displayed by other groups of organisms. Dr. A. G. 
Mayer made an initial biological study of the Tahiti land-snails belonging 
to the genus Partula and found remarkable differences between the 
valley colonies of this island. Advised by him to carry investigation 
further, I undertook the journeys mentioned, and the present brief 
account of the last one will give some of the general results of studies 
in the field and laboratory. 
The first landing place as in previous voyages was the island of 
Tahiti, the largest and best known member of the Society Islands. 
Papeete is its main town, situated on the northwest coast, and like Suva 
in the Fiji group and Honolulu in the Hawaiian group, it is the govern- 
mental and commercial centre of the surrounding region of the South 
Seas. Its great prominence has been gained from Captain Cook’s 
famous voyages in the eighteenth century and from the establishment 
here of the earliest missionary settlements in southeastern Polynesia. 
The town now has over 3,000 inhabitants, about three fourths of whom 
are natives. Cook’s estimate of the population of the entire island made 
in 1765S was 240,000 whereas now there are less than 10,000 natives. 
‘ven if we allow for considerable exaggeration in his estimate there has 
obviously been a frightful mortality, resulting from their contact with 
white races and from the almost total destruction of their primitive 
scheme of life. 
On approaching ‘Tahiti, the island reveals itself as a magnificent 
double cone of ancient volcanic rock; the larger cone is twenty-five miles 
in diameter and rises to a height of nearly SOOO feet; it is joined by a low 
narrow isthmus to the smaller cone which is fifteen miles across. ‘The 
view of the island near Papeete (page 123) shows also the characteristic 
mountain ridges whose central heights are covered by clouds from soon 
after sunrise to sunset. ‘These ridges radiate with remarkable regularity 
from the interior to the sea, and the valleys between them are sometimes 
a half-mile in width, with dense tropical vegetation along the more level 
ground on either side of the streams. Sometimes the valleys are deep, 
narrow gorges with high, steep walls, bare of everything except low shrubs 
and grass. It is in the moist jungles of the valley bottoms that the 
Partulas live, and the higher and drier slopes form boundaries that 
restrain the snails from crossing to another valley, except during the 
wettest months of the rainy season. 
More than two hundred valleys of smaller and larger size have been 
