INTRODUCTION. 
THE PROBLEMS, THE RESEARCH, AND THE GENERAL RESULTS. 
The present memoir is the first of a series which is designed to give the results 
of recent studies upon the problems of variation, geographical distribution, and 
evolution in the case of certain Polynesian lung-snails belonging to the genus Partula 
of Ferrussac. The genus is restricted to the islands of the Pacific Ocean, and its 
headquarters are in the Society Islands in the southeastern part of Polynesia, 
although several species occur in Melanesia and Micronesia, as well as in other 
groups of islands at greater or lesser distances from the headquarters of the genus. 
In the course of the investigations upon which the present account is based, the 
species and varieties of this genus were studied not only with regard to their indi- 
vidual characters but also in connection with their general biological conditions, 
their geographical and topographical locations, and their apparent control in cer- 
tain respects by meteorological and other external influences. In general terms, 
therefore, the subject of study may be stated as the natural history of the genus 
Partula, including the present ecological and past evolutionary relations of the 
various species. 
Four journeys of exploration have been made. During the hot and rainy 
season of 1906, six weeks of the months of February and March were devoted to a 
first study in the island of Tahiti, which is the largest and most accessible member 
of the Society Group. In 1907 more than seven weeks of the months of June and 
July were spent in further explorations in Tahiti and in its near neighbor, Moorea, 
during a season which is slightly cooler and drier. In the corresponding season of 
1908 a third period of field-work extended over the greater part of June, all of July, 
and the larger part of August, and during this time an almost complete survey was 
made of the islands of the so-called Leeward division, namely, Raiatea, Tahaa, 
Huahine, and Borabora, of which the first-named is by far the most important of 
all the places inhabited by Partula as regards the number of its species. Finally, 
in 1909, a fourth journey, comprising seven months, began again with field-work 
in Tahiti, Moorea, and Raiatea, in order to complete the study of certain important 
areas of these islands, and it was subsequently extended so as to include the Cook, 
Tonga, Samoan, New Zealand, Fiji, and Hawaiian Islands. Some material was 
obtained and many important observations were made in the Cook or Hervey 
Group, while in Samoa a month devoted to exploration yielded fairly satisfactory 
results in Upolu, although further studies are necessary to complete the investiga- 
tions in this group. In the Hawaiian Islands, through the courtesy and kindness 
of Director Brigham and Dr. C. M. Cooke, of the Bishop Museum, the famous 
collection of Partule made by Andrew Garrett was thoroughly studied; a few 
excursions were made for the study in the field of the classic Achatinellide, whose 
ecological and evolutionary relationships are of the utmost importance in connection 
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