INTRODUCTION. 
NATURE AND BEARING OF PRESENT INVESTIGATION. 
The present volume is the second to be completed in a series of detailed 
analytical studies on the genus Partula. The first volume! dealt with the species 
of Tahiti, the largest and best-known member of the Society Islands, situated in 
southeastern Polynesia. The studies on the representatives of the genus that 
inhabit Tahiti may well be designated fundamental, both because the Society 
Islands constitute the present headquarters of the whole genus, and also because 
the investigations in question served to develop the methods by which the subjects 
of variation, distribution, and evolution in the case of other island associations 
may be analyzed, to the extent that time and opportunity may determine. 
While it had been expected that the second volume to be prepared would deal 
with the species of Moorea—an island adjacent to Tahiti in the Society Group— 
that expectation has not been realized, first on account of the Great War and its 
prior claim on the services of the writer, and second because the field-work in that 
and other islands of the headquarters group remained to be completed. Mean- 
while, in 1920, an occasion presented itself for a study of Guam and its neighbors in 
the Mariana Group, located in the western Pacific Ocean. The opportunity was 
seized because, with the foundation laid in the studies of the genus at its head- 
quarters, it was thought that an investigation of an outlying territory would serve 
to bring into clearer relief such basic principles of ecology, distribution, and relation- 
ship as were common to widely-separated areas which might be somewhat unlike 
in secondary details. The event has justified the decision, in ways that will be 
described in subsequent sections of the present volume. 
A long-deferred leave from academic duties at Barnard College afforded the 
opportunity to which reference has been made and the months of July and August 
of 1920 were allotted to the investigations in the Mariana Islands. Being at the 
time Curator of Invertebrate Zoology at the American Museum of Natural History, 
plans were developed in the interests of that institution for extensive collecting 
in areas of Micronesia, southeastern Asia, Malaysia, and Australia; and in the 
consummation of these plans additional information regarding tropical ecology 
was gained. ‘The present research was made possible by the generous support of 
the Bernice Pauahi Bishop Museum of Honolulu, for it seemed to Director Herbert 
E. Gregory and to the Trustees that the ecological investigations proposed by the 
author would be useful in connection with their comprehensive explorations of 
the whole Pacific area as well as in relation to the intensive studies upon terrestrial 
gastropods long carried on by C. Montague Cooke; the author’s grateful acknowl- 
edgments to the administrative and scientific staff of the Bishop Museum are 
herewith and all too briefly recorded. 
1H, E. Crampton, Studies on the variation, distribution, and evolution of the genus Partula. The species inhabiting Tahiti. Carnegie Inst. 
Wash. Pub. No. 228, 1917. : 
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