216 VARIATION, DISTRIBUTION, AND EVOLUTION OF THE GENUS PARTULA. 
FaoneE VALLEY. 
In this last case the plain adults amount to 88 per cent of the population. The 
classified gravid parents are as follows: 
Plain adults: plain young, 175; both kinds, 0; banded young, 8=183 
Banded adults: plain young, 18; both kinds, 2; banded young, 15 =35 
Here the average number of young is little over 1 to each fecund adult, and 
hence a larger correction has to be made in dealing with the figures of the second 
line. The proportions of DD, DR, and RR are 4, 28, and 3, respectively, when the 
first assumption is made, when the difference between the empirical and expected 
figures for the first line amounts to 6 out of 183, or 3.3 per cent. On the second 
hypothesis, namely, that the absence of bands is recessive, the proportion of DD, 
DR, and RR are the clearly unnatural ones of 1:21:161, and the departure of 
actual from expected figures is 2 1n 35, or 5.4 percent. Here again the first assump- 
tion gives more credible and consistent results. 
In brief, the facts indicate (1) that the absence of bands is dominant to their 
presence, and (2) that a Mendelian order of inheritance is followed by these alter- 
native characters. 
SUMMARY AND CONCLUSION. 
Bringing together the principal results of the foregoing detailed studies in order 
to emphasize the general features of significance, almost the same statements must 
be made as in the case of rubescens, for the fundamental principles of distribution 
and variation are essentially similar in nature and meaning. The material is more 
complicated, however, through the sporadic occurrence of sinistral mutants among 
the predominant dextral snails, whereas rubescens is invariably sinistral, while the 
variations in coloration are more numerous and more sharply distinguished than in 
the case of the contrasted variety. We need not now deal with the extrinsic rela- 
tions of affinis, for these are best considered in a review of the whole species at a 
later point; at present, the intrinsic features are the objects of attention. 
I. As a primary variety, affinis is distinguished by its dextral coil, small size, and 
brownish coloration, but 1t 1s not invariable in these respects. Sometimes it is reversed, 
and in some localities the shells are much above the average in size, while here and 
there the red coloration is displayed by occasional individuals or by a large propor- 
tion of the colony, as in Farapa. It occupies essentially the same territory as in the 
earlier decades, when Garrett made his studies. 
Il. The colonies of affinis vary in their make-up as regards the relative numbers in 
the whole Partula population and in the otaheitana population, as well as in the pro- 
portionate numbers of dextral and sinistral components and of the constituent color- 
classes. Such variations may not be referred to diverse environmental conditions; 
P. hyalina and P. clara exist in the same areas as they do elsewhere; rubescens 
accompanies affinis in nearly all of its valleys, while sinzstrorsa is its associate in 
some parts of Taiarapu. Yet these other types do not display the complex of 
characters that distinguish afinis. 
