146 VARIATION, DISTRIBUTION, AND EVOLUTION OF THE GENUS PARTULA. 
TaBLe 82.—Partula otaheitana amabilis, Ururoa Valley. Statistics of tooth development. 
Standard 
deviation. 
Series. : None.} Trace.| Tooth. | Large. | Very large. Mean value. 
Sinistral plain 2.6530 .0276 0.7535 .0195 
Sinistral, banded 50 site 2.0000 .3179 . 8165+ .2248 
Sinistral, all 2.6473 .0275 . 7565+ .0194 
Dextral, plain x Be id 58 3.0000 
The single dextral shell agrees sufficiently with the plain sinistral group to 
justify the belief that it is a product of a parent belonging to the latter; there are 
no grounds for regarding it as a migrant from another valley, for such sports do not 
seem to occur in Pohaitara, while a dry zone intervenes between Ururoa and Tuauru 
where the true dextral affinis exists. 
Like the Pohaitara colony, this series displays a remarkably low degree of 
fertility, at least at the time of observation (table 83). 
TaBLe 83.—Partula otaheitana amabilis, Ururoa Valley. Fecundity. 
No. of | Per cent | No. of | No. of Total Average | Average 
SSE ‘| gravid.| gravid. eggs. | young. | contents. | for gravid. | for all. 
Sinistral, plain 
Sinistral, banded 
Dextral, plain 
Of 19 embryonic young borne by plain sinistral parents, all were sinistral, 
various shades of brown, and unbanded. ‘The aberrant individuals, unfortunately, 
were barren of advanced embryonic contents. 
GENERAL SUMMARY. 
Having completed the detailed analysis of the primary variety amabzilts as it 
exists in each of the four valleys of its range, we are in a position to treat it in a 
broader way so as to bring out more clearly its relation as a whole to the basic group, 
P. otaheitana otaheitana of Fautaua, and to compare the distinctive features of each 
of its four component colonies. 
I. The colony of each valley is distinguished by certain general peculiarities of 1ts 
composition as a whole (table 84). In Hamuta the large proportion of dextral 
individuals is a prominent differential characteristic. The Pirai colony is unique 
because of the large proportion of light-colored shells in its exclusively sinistral 
population. Pohaitara is inhabited by reversed snails only, but more than half of 
them are yellowish-red or “medium” in ground-color. In Ururoa the distinctive 
features are the preponderance of reddish-brown shells and the sporadic occurrence 
of banded sinistral snails as well as of plain dextral individuals. The uniform 
environmental conditions obtaining in the sector where these valleys lie can not be 
accountable for such diverse colonial characteristics as are manifested in the direc- 
tion of the coil and in ground-color. 
