PARTULA OTAHEITANA. 129 
to determine with exactness the precise color-class to which an embryonic snail 
should be assigned, on account of the relative thinness of the newly-formed shell; 
hence too much stress should not be laid upon discrepancies between the propor- 
tionate numbers of young and adults in the several classes. 
The salient points established by the detailed observations are as follows: 
(1) The dextral individuals that bear young number 43.7 per cent of the three 
annual series taken together, while dextral young snails constitute 50.7 per cent of 
the whole number. We are justified in concluding, then, that the dextral character 
is now in the ascendant, after a long period of sinistral dominance. 
(2) The banded and plain classes are not physiologically separate. The single 
gravid snail with a banded shell bore one plain young of Class II; of the offspring 
taken from the plain adults not a single specimen showed distinct bands, although 
such might have occurred with the peculiar coloration so faint as to escape detection. 
The one plain snail from the banded parent is best interpreted, I believe, as a 
reversion to the simple type, perhaps in the Mendelian sense of a dominant-recessive, 
where the mutant character would be the recessive of the couple. Obviously more 
data are required before this interpretation should be adopted, even provisionally. 
(3) The color-classes are not physiologically distinct. With the exception of 
Class I snails, the characteristic color breeds true in less than 50 per cent of the cases. 
The situation is too complex to permit an analysis in Mendelian terms, even though 
the material is abundant. To settle the question as to a Mendelian course of 
heredity, experiments are absolutely essential. 
SUMMARY AND CONCLUSION. 
The snails of the Fautaua colony form an extremely complex stock, whose 
members differ in characters of many kinds, viz, color and coloration, direction of 
spirality, dimensions, and proportions. It will appear that this complex stock 
stands in a parental relation to the diverse colonies of other valleys and regions; in 
any one of the latter the shells exhibit one combination or another of the so-called 
unit characters displayed by the Fautaua group as a whole. For example, they 
may be exclusively sinistral, yellow or red, but never brown, universally devoid of a 
tooth, and large, as in P. otaheitana rubescens; or they may be always dextral, brown, 
strigated, with a well-developed tooth, like some of the isolated groups of P. ota- 
heitana affinis. In no valley, however, are any distinctive characters added to the 
complex of the Fautaua colony. 
The alternative view that P. o. otaheitana is a synthesis of diverse stocks which 
originated elsewhere and whose emigrants have met in Fautaua Valley presents 
itself as a possibility, but it is not supported by the facts which will appear as we 
proceed. A significant detail is that migration from one valley to another is all but 
impossible in the northwestern region where Fautaua lies. Again, characteristics 
such as the large size, clear red and yellow ground-colors, and invariable sinistrality 
displayed by rubescens of Oopu Valley in their purity could scarcely have been 
contributed by such a far-distant community to the colonial qualities of the Fautaua 
group. All points considered, it seems more logical to regard P. otaheitana ota- 
