CHAPTER IX. 
RESUME. 
INTRODUCTION. 
The investigations described in part in the present volume are concerned with 
the natural history of land-snails belonging to the genus Partula of Férussac. In 
the course of four journeys of exploration in Polynesia, the author has collected an 
abundance of material which makes it possible to study specific variation, distribu- 
tion, and evolution by using the precise quantitative methods of biometry, always 
with a view to the assignment of definite relative values to the congenital and 
external factors of differentiation. The results as they are given for the forms of 
Tahiti and as they will be presented in subsequent volumes constitute an analysis 
of the existing situations and conditions of the several species, interpreted to some 
extent in terms of the earlier descriptions given by Garrett and Mayer, while in 
addition they provide a sure basis of comparison for similar comprehensive investi- 
gations that may be prosecuted after the lapse of decades. 
CHAPTER I. 
The organisms under consideration live on certain of the oceanic islands of the 
south and west Pacific Ocean with headquarters in the Society Islands, of which 
Tahiti is the largest and best-known member. [Each group and each inhabited 
island bears characteristic species not found elsewhere, with only rare and peculiar 
exceptions; hence the geographical conditions are ideal for the study of the correla- 
tion between the degrees of resemblance exhibited by the species and the degrees of 
proximity or isolation of their territories. Almost without exception the snails 
occur on the larger “high”’ islands of ancient volcanic construction, where they 
live in the moist areas of the valleys, in more or less isolated colonies. An analysis 
of the geological, climatological, and barometric conditions rules out such elements 
as factors of differentiation, although they set the limits to the areas within which 
the organisms may maintain themselves. Although the food of the animals consists 
of decayed vegetable matter, there is no discernible relation between a given 
species and a definite botanical associate. 
; CHAPTER II. 
The present volume deals with the species of Tahiti only. In the course of the 
writer’s field work, more than 25,000 adult specimens were obtained, together with 
over 7,000 adolescent individuals; as the snails are viviparous in habit, many 
thousands of the offspring which exhibit their taxonomic peculiarities have been 
dissected out of the brood pouches of their parents. 
Eight species in all are recorded from Tahiti, namely P. hyalina Broderip, 
P. clara Pease, P. jfilosa Pfeiffer, P. nodosa Pfeiffer, P. otaheitana Bruguiére, P. 
producta Pease, P. attenuata Pease, and P. stolida Garrett. ‘The last two have not 
been investigated like the others; P. attenuata is a rare inhabitant of the highest 
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