Physiological problems of the geographical distribution of Partula in Polynesia, with demonstration of specimens

Abstract

The speaker described briefly the geographical features of the distribution of Partulæ in Polynesia, known through the researches of Mayer, Garrett, Cuming, and others, as well as from personal observations. The snails of this genus are so distributed that each archipelago and each island where they occur possesses unique types, while often single valleys will comprise the habitat of a species. Only two exceptions to the former statement are known. A detailed demonstration was made of the snails from 55 valleys of Tahiti, and from 19 valleys of Moorea, the two islands of the Windward division of the Society group. The present communication consisted chiefly of a description of the features presented by the demonstrated valley populations. The general conclusions of the survey are (1) that there is a general correlation between geographical proximity or isolation on the one hand and specific resemblance or divergence on the other hand; (2) that some species (e. g., P. hyalina) are wide-spread and relatively invariable, while other forms exhibit variations and mutations that seem to be the antecedents of fixed independent varieties of the future; (3) and that variation does not seem to be referable to environmental influences.