172 VARIATION, DISTRIBUTION, AND EVOLUTION OF THE GENUS PARTULA. 
Next comes the question as to the stability of the colonies as indicated by the 
returns.. From the figures as given in table 114, it is apparent that the gravid 
adults constitute entirely satisfactory reproductive samples, so to speak, of their 
respective associations. Specifically, the proportionate numbers of yellow and red 
individuals are essentially the same among the parents with classifiable young as 
among the adults generally. The discordant instances of Tautira and Aiarua 
occur because circumstances prevented a study of a sufficient number of adults 
collected; but when we compare the offspring generation with the adults, it appears 
that wherever both color-types occur in a colony the percentage of red snails among the 
offspring is less than the relative numbers of this kind in the adult population and in the 
group of gravid adults, with two exceptions of slight degree in the upper list (Ahonu 
and Oopu) and two in the lower list (Tiarei and Aiurua). In the case of Helix, 
Lang found that the dominant red color was not always displayed by very young 
snails, but appeared only later; if the genetic facts are the same for P. 0. rubescens, 
the smaller percentage of the red type in embryonic populations would be explained. 
In the next place, we encounter a difficulty which prevents the combination of 
the reliable figures for the colonies of the six first-listed valleys into a single series, 
the fact, namely, that the proportionate numbers of yellow and red individuals are 
not the same in any two valleys, although, as qualified above, they are essen- 
tially stable within the valley. One of these two classes comprises recessive indi- 
viduals (RR) only, while the other is made up of duplex dominants and heterozygous 
snails (DD+DR). The proportions of these three genetic classes can not be the 
same in Haavini, where the red-shelled snails number only 3 per cent, as in Oopu, 
where such individuals amount to 64 per cent, and hence the figures can not justly 
be combined. 
Each valley association, therefore, must be taken by itself for internal analysis. 
The problem is to ascertain whether the facts warrant the assumption that one 
color-type or the other is dominant with reference to its alternate as a recessive, and 
whether the characters of the young borne by the gravid parents make it possible 
to assign the adults to the three classes, DD, DR, and RR. 
Oopru VALLEY. 
The colony of Oopu Valley will be taken up first, on account of its apparent 
stability, and also because larger numbers are at hand for the development of the 
method by which a Mendelian analysis may be made. At this point, however, 
it must be frankly stated that the result in this case, taken by itself, would indicate 
the recessive character of the red color-factor, which is contrary not only to Lang’s 
results but also to the final conclusion of the present study. 
A. Red color assumed to be dominant.—The gravid adults and their young pro- 
vide the data for the treatment of the Mendelian problem. The former are to be 
classified according to the color characters of their embryonic young, and each 
parent is to be counted once only, with the following numerical relations: 
(1) Red adults: red young only, 98; red and yellow young, 7; yellow young only, 16=121 
(2) Yellow adults: red young only, 19; red and yellow young, 16; yellow young only, 39=74 
