142 VARIATION, DISTRIBUTION, AND EVOLUTION OF THE GENUS PARTULA. 
Classes I and II, while the dark classes receive recruits from light-colored divisions. 
Interbreeding among the members of the several classes seems to occur; at least 
the recognizable divisions are not absolutely isolated in an hereditary sense. 
TaBLeE 76.—Partula otaheitana amabilis, Pirai Valley. Statistics of fecundity. 
No. of | No. of | Total 
eggs. 
Average Average 
for all. 
Per cent 
Series. : 
gravid. 
young. |contents.| for gravid. 
43 
. 56 
ot 
Sinistral, plain, all 
Sinistral, banded, 1906.... 
IO sob 
1903Ree 
1909.... 
Fut Data. SUMMARY. 
Young. 
eras Ae ee Banded.| Total. Plain. Banded. Total. 
Adults: Adults: 
Plain, Class) Ic. 350 5 355 Plaines 426 1 427 
1B bo 6 61 3 1 65 (97.48 p. ct.] 
0 lon 4 3 7 Banded. . 7 11 
War fi we [2.51 p.ct.] 
IBandedtereeeer 7 4 11 ———— 
shotalerane 433 5 438 
motalepeer aie. 422 11 5 438 [98.85 p.ct.] ] [1.14 p. ct.] 5 
CONCLUSION. 
In its collective aspect, P. 0. amabilis of Pirai Valley departs from the Fautaua 
association to a greater degree than does the colony of Hamuta. Its distinctive 
features are (1) the absence of dextral components; (2) the preponderance of light- 
colored shells; and (3) smaller dimensions in all sections of the colony. The last- 
named quality is one that will appear more clearly in the summary treatment of 
the whole variety. 
POHAITARA VALLEY. 
The northern geographical sector, between Pirai and Tuauru Valleys, contains 
several narrow gullies or ravines of considerable radial extent, but of relatively 
shallow depth. The stream-bed rises rapidly as it is followed inland, so that its 
gradient is very nearly of the same angle as the profile slope of the ridges on either 
side. Valleys of this kind, which are relatively open and dry, belong to the quater- 
