PARTULA OTAHEITANA. 291 
While at first it might seem legitimate to ascribe the changes noted on passing 
inland to some environmental condition which became intensified in its effect in 
the higher parts of the valley, this would scarcely be logical in view of the contrary 
results discovered in the study of associations in other valleys, notably Taapuna, 
Papenoo, and the series inhabited by amabilis. Sometimes the inhabitants of the 
lower valley are small, as in Taapuna, but more often they are larger. It is possible, 
of course, to interpret the larger size of the extreme inland series—that of 1g09—as 
the result of a selective process, for the conditions in the uplands are adverse as 
compared with those of the middle valley, and weak individuals also would find 
greater difficulty in reaching maturity. The anomalous fact would remain, however, 
that the series of 1906, from the lowest ground, where again adverse conditions are 
to be met, is made up of shells that are smaller in absolute measures. Without 
appealing to selection, another explanation of the facts might be found in the diverse 
heritage of snails living in the lowermost and uppermost areas of the whole inhabited 
range; the intermediate series of 1907 would then become to some extent a mixture 
of the two extreme stocks, and would naturally display a statistical intermediacy. 
Certainly the 1909 association is different from the rest in some respects, specifically 
in that sinistral elements occur in it; and such diversely coiled individuals do not 
constitute an independent stock, but they are relatives in statistical qualities, while 
furthermore their genetic relationship to the dextral members is proven by the data 
of heredity as given below. However we may interpret them, the statistics show 
that the snails of different areas in the inhabited range possess diverse minor 
qualities. 
FECUNDITY. 
The statistics of fecundity (table 246) bring out certain interesting results. 
The series of the wet season, 1906, shows a low percentage of breeding individuals, 
but a fair rate of productivity on the part of such as are gravid. ‘The series of 1907, 
TasBLe 246.—Partula otaheitana lignaria, Tipaerui Valley. Fecundity. 
No. of | Percent] No. of | No. of Total Average Average 
Beties. gravid.| gravid. | eggs. | young. | contents. | for gravid. for all. 
.05 
61 
.69 
1906, banded, light : : .95 
medium.... : ; 50S 
.65 
1906, all dex : f .69 
1907, plain F : ih lal 
banded : : othe 
1907, all dex . j aly 
1909, plain, dex : : .94 
banded, dex : 56 ss 
1909, plain, sin , ; .53 
banded, sin P ; ol 
.89 
. 04. 
