PARTULA OTAHEITANA. 297 
ancestral stock ranged over the whole land-mass, and that its local products 
differentiated into the distinct species after the process of subsidence had isolated the 
mountains now forming the separate islands. he alternative view is that human 
carriers have introduced ofaheitana into Moorea and Raiatea, there to assume new 
characteristics, or that some one of this group of species is immediately ancestral 
to the others. But this seems less tenable than the one adopted, especially in view 
of the collateral evidence that Partula attenuata exists in Tahiti and Raiatea, in the 
upper part of the valleys, and upon the higher branches of the trees; the human 
factor is certainly eliminated in such a case, and there is no more reason to postulate 
its interposition in the case of otaheitana and its relatives. It is true that other 
products of the ancestral stock might have persisted for a time in Tahiti in company 
with otaheitana, or in Moorea, but if they did they have long since disappeared; 
even so, the essential principle involved remains the same without qualification. 
III. The original pro-otahettana stock of Tahiti, after the isolation of the island 
became resolved into the eight primary varieties herein distinguished, viz, otaheitana 
sensu var., amabilis, rubescens, affinis, the sinistrorsa-sinistralis-crassa series, and 
lignaria. While questions arise as to the location of the areas where each took its 
present form, these may be passed over for the time in favor of the problem con- 
cerned with the reality of the interrelationships among the several divisions of the 
species. These have come to differ to greater or lesser degrees, it is true, and are so 
situated geographically that they can not generally interbreed, yet collectively they 
are well separated from the other forms of Tahiti and are morphologically related 
to one another; the facts given in detail in the circumstantial analysis provide the 
requisite evidences. 
Among the more interesting and significant points to be recalled in this connec- 
tion are the sporadic manifestations in one variety of characters that are distinguish- 
ing marks of another division. For example, the sinistral coil that is exclusive in 
rubescens and dominant in the sinistrorsa-sinistralis-crassa series occurs by muta- 
tion in affinis and lignaria, which are usually dextral; conversely, the dextral 
character of the latter varieties is displayed by a few or by many individuals in 
colonies belonging to the triple reversed series of the south and west; the red and 
clearer yellow colors of rubescens appear infrequently in affinis, but they constitute 
the distinctive colonial qualities of crassa occidentalis of Aoua and Papehue Valleys, 
whose typical relatives are brown; the bicolored pattern is produced in one colony 
of rubescens and in two widely separated associations of affinis; giant adolescents far 
above the average appear in affinis and in sinistrorsa, which attain the great size of 
best-developed rubescens shells; dwarfs are found in certain rubescens and other 
colonies among snails that are usually large. 
The relationships in question being recognized, the next point is that the present 
otaheitana otaheitana association of Fautaua Valley best represents the original 
ancestral stock of the species, for only in that colony do we find all of the character- 
istics that are displayed in one or another combination by the distinguishable 
varieties. While the condition of otaheitana otaheitana might conceivably be 
brought about by a synthesis of characters contributed by two or more well- 
