RESUME. 311 
contend that, because two distinguishable types occur in neighboring localities, 
there must be environmental factors for the observed differences; but even this 
argument breaks down when individuals of a mutant group, like dextral sinzstrorsa, 
appear in a valley along with their unchanged relatives. In a word, the role of 
the environment is to set the limits to the habitable areas or to bring about the 
elimination of individuals whose qualities are otherwise determined—that is, by 
congenital factors. 
CHAPTER VIII. 
For the sake of completeness, a description is given of the species P. producta 
Pease, which is the complete antithesis of otaheitana both in its terrestrial habit and 
in its confinement to a limited area in the southeastern district of Mataiea. In 
general form, and to some degree also in its coloration, producta resembles the other 
species named, but in the details of both groups of characters it is distinct. 
Here there is no opportunity for a study of distribution. The distinctive 
features of producta and its intrinsic variation are of some interest, especially in 
connection with a wider treatment of the terrestrial species of the genus, which will 
take into account the forms with similar habits that exist in other islands like 
Raiatea. For the present this species stands out on account of its contrast with its 
associates on the island of Tahiti. 
