CHAPTER VII. 
PARTULA OTAHEITANA Bruguiére. 
GENERAL CONSIDERATIONS. 
By far the greater part of the Partula population of Tahiti consists of rep- 
resentatives of P. otaheitana Bruguiére, which exists in one or in several of its 
manifold forms in all of the valleys of Tahiti explored in the course of the present 
investigation where any snails whatsoever were secured. Undoubtedly the species 
occurs in some of the smaller ravines, where, however, the shallow vertical depth 
of the valley, the lack of deep shade, relative dryness, and the scarcity of decaying 
succulent plants render its situation precarious and its numbers few. There is good 
reason to believe, nevertheless, that all of the variations of this species are repre- 
sented in the collections of the present research; these comprise more than 20,000 
adults and 6,000 adolescents, together with several thousand embryonic snails 
dissected out from their parents, which were sufficiently advanced in development to 
show many of their specific and varietal characters. 
The wealth of material renders it possible to make an exhaustive analysis of 
the colonies living in different areas. The circumstances are such as to make this 
species more valuable than any other for the purposes of the present research; 
indeed, its analysis forms the surest basis for the views herein and hereafter expressed 
as to the relative values of hereditary and environmental factors in the evolution 
of the several species constituting the whole genus. It is true that through the 
study of P. hyalina, P. clara, and P. nodosa definite conclusions are established, 
all the more readily because those forms are relatively simple as regards their intrin- 
sic diversifications and their geographical range; but all of the relations that they 
display are repeated in P. otaheitana, amplified to the fullest possible degree, while 
others are added. In brief, the favorable conditions are (1) the existence of the 
species in practically all habitable areas of the island; (2) the large numbers obtain- 
able in nearly every valley; and (3) its extraordinary differentiation into varieties 
of primary, secondary, and tertiary degree, as a result of which it has become the 
most complex of the known species of Partula. 
The incidental comparison with the situation of former decades as depicted by 
earlier writers is made somewhat difficult and at times impossible by the existing 
confusion in the taxonomy of the species as a whole. From fifteen to twenty 
specific names have been given to the various “forms”’ of P. otaheitana by systema- 
tists who (with the exception of Garrett and Mayer and those who have relied 
upon their explicit statements) have been wholly ignorant or neglectful of the exact 
localities in Tahiti from which their “types” were obtained. Data of this kind 
are absolutely indispensable, and Garrett’s monograph places the student of dis- 
tribution under great obligations because the forms he distinguishes and describes 
are invariably located with substantial accuracy. While it is true that some slight 
errors may be detected, these no doubt arose because of the lack of complete maps 
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