170 VARIATION, DISTRIBUTION, AND EVOLUTION OF THE GENUS PARTULA. 
the main, we must come to the conclusion stated above, or else deduce as an alter- 
native that the dark apical coloration is tending to disappear as an hereditary quality 
of the Oopu colony. 
APIRIMAUE VALLEY. 
In this valley association a single reddish shell was found (plate 28, fig. 23), 
which is anomalous only in its small size as compared with the rubescens of Oopu. 
In the general color, darkened apex, faint pink lining within the lip, in the absence 
of the columelia tooth, and in its smooth surface, this shell agrees with rubescens in 
general. The majority of the members of this colony are sinzstrorsa and reversed, 
but their coloration and shape are such as to exclude the anomalous individual 
from their kind. Also in this valley there are a few affinis with the dextral coil; 
but they are brown, toothed in most cases, and bear only dextral young. Taking 
all the data into consideration, we may justly conclude that the single red-shelled 
sinistral snail is a dwarfed rubescens, in some respects like the animal of reduced 
size that was found in Papeiha Valley. 
The class-values of the measurements are as follows: 
Shelllensth ue ace ee sacrament ctatne ceCr Cr Orree 16.75 mm. 
Shrelliswid thts. sercac tee sisters orcas eae excuse ees ota yee terete: 10.30 mm. 
Shelltproportiontis, 4. pone er ee erin De CoO 60.5 per cent. 
Apertureilength =p ncyaseoee cecisi ne a lseetretne satis Oe eee 8.70 mm. 
Apertureswid thrrsacrcniin icteric eee eee Cnc 7.30 mm. 
/MNSTAT FORO) DOMES 0 0 000000000000000000000000000000000 83.5 per cent. 
Length aperture + length shell, proportions................. 51.5 per cent. 
Ae eenaraeroonesouaadadaaadaaduus a Gap OOShoU Su aduados None. 
No embryonic contents. 
A MENDELIAN INTERPRETATION OF THE HEREDITY OF COLOR. 
Throughout the foregoing circumstantial analysis of the several colonies of 
rubescens, the figures relating to the heredity of contrasted yellow and red ground- 
colors have been given without extended comment, or with only a passing suggestion 
as to their wider significance. It is now in order to re-examine the data in an 
endeavor to ascertain whether they indicate a Mendelian mode of inheritance of the 
two principal colors, with the explicit understanding that whatever its analysis and 
its results may be, the final formulation in Mendelian terms must depend upon 
actual experiments, and can not be made solely on such numerical returns as are 
given in the present descriptive account. When one deals with the phenomena of 
heredity in wild populations, many difficulties are encountered that are well-nigh 
insuperable; nevertheless, a method for the analysis of such associations of Partule 
has been devised. Its results suggest, even if they do not conclusively demonstrate, 
a dominant-recessive relation of the red to the yellow color, and a Mendelian order 
of their inheritance; hence the conclusions are like those of Lang, who dealt experi- 
mentally with identical characters displayed by snails of the genus Helix. 
The fundamental fact is that wherever the population is mixed the heredity 
of the ground-color is alternative: an adult or an embryonic shell must be assigned 
either to the “yellow” class or to the “red”’ class. Varying shades of the former 
color are displayed, even to the whiteness of more or less decorticated individuals, 
