a - > = 
248 VARIATION, DISTRIBUTION, AND EVOLUTION OF THE GENUS PARTULA. 
a native will secure young plantains from one valley for establishment in a region 
nearer his home, although the wild plants are usually abundant everywhere. In 
such a case, any Partule that were sealed up upon the young leaves might remain 
attached and so be transported to a valley where its kind did not exist. Assuming 
them to be already gravid, or assuming that several animals were thus carried to a 
new place, the type might thus be established in another region. 
Tas Le 193.—Partula otaheitana sinistrorsa. Progressive geographical comparisons. Differences in mean value. 
Shell. Aperture. Length aper- 
Valley. Ea ea heor Tooth, index. 
Length. Width. Proportions. Length. Width. Proportions. tions. 
Vaiaaia...... mm. mm. Duct: mm. mm. Ducts p. ct. 
[ +0.0013 = .0646]|—0.1462 = .0343 | —0.6084=+.1608 | —0.3126+.0366 |—0.1600+.0293 | +0.7087=.2032 | —1.5176=.1310| [0] 
payor es +1.2729+ .0645 | +.3666+.0325 | —1.6280+.1499 | + .5305+.0347 | +.2272+.0276 | —1.5969+.1755| — .5570+.1171} [0] 
ae ee + .4132+.0645 |[+.0142 + .0323]] —1.0209+.1485 | + .1387+.0359 [—.0012+.0279], —1.0462+.1672| — .3466+.1154] [0] 
ere eae —2.4185+.0609 | —.7565+.0314 | +2.6915+.1433 | —1.1852+.0340 | —.7105+.0257 | +1.7484+.1646 |[+ .0014+.1138]] [0] 
ee + .3574+.0609 | +.2080+.0331 |[+ .0676+.1715]) + .5225+.0318 | +.3705+.0263 [— .0170+.1954]) +1.8622+.1235 | +0.0774+.0188 
aaa a ath — .6467+.0589 | —.2260+.0301 | + .6709+.1672| — .3025+.0307 | —.1193+.0254 | +1.1168+.1877 |[+ .0963+.1206]| — .0478+.0199 
eee —1.0988+.0590 | —.3722+.0310 | +1.2806+.1634| — .6966+.0336 | —.3795+.0253 | +1.5741+.1942| — .6478+.1318] + .0756+.0203 
i ae Sis + .2693=.0560 | —.0777+.0305 | —1.1757+.1602 | + .1123+.0325 |[+.0154+.0245]) — .8905+.1961 [— .2187+.1307]] — .1052+.0193 
ee ce — .1789+.0442 | —.1112+.0232 |[— .0568+.1213][+ .0140+.0247]| —.0375+.0184| — .5974+.1455| + .5896+.0997!| [0] 
Vairaharaha. . 
+2.0076.0465 | +.8844+.0251 | —1.1891+.1143 | 4+ .8266+.0265 | +.6212+.0199 [+ .0995+.1365]) —1.0168+.0954 | + .0903+.0109 
ane —1.4601=.0423 | —.6694+.0221/] + .6754+.1008 | — .6222+.0230 | —.4500+.0179 | + .2358+.1146| + .6306+.0834} + .2254+.0220 
ay ees [— .0740+.0388][+.0254+.0199]| + .3719+.1042 |[4+ .0330+.0227]|[ —.0030+.0174])| — .4077+.1298| + .3345+.1072 |[+ .0414+.0303 
ak “|| —1.3048.0377 | —.4384.0200 +1.6196+.1014} — .6119+.0227 | —.4549+.0176 [+ .1967+.1324]] + .3090+.0879 | +1.3226+ .0330 
eohw | Rear 
Yet the facts as observed are explicable on either of the assumptions stated: 
(1) The Taiarapu shells are exclusively sinistral. Migrants from Tahiti nui 
would be sinistral on the law of chances, because this is the prevalent mode of coil; 
but snails brought passively on vegetation would also be preponderatingly reversed. 
(2) The Taiarapu snails are exceedingly large, on the average. Only well- 
grown and vigorous individuals could successfully traverse the drier region of the 
isthmus so as to reach Taiarapu; but again only large snails would be likely to 
survive the interval between the cutting of a plantain secured in Tahiti nui and its 
replanting in a Taiarapu valley. 
(3) The three color-classes of Mataiea valleys are not represented in all of the 
peninsula area; whether brought by their efforts or by human agency, the first 
sinistrorsa inhabitants in Taiarapu would naturally be few, and would scarcely 
be representative of all the color-classes. Were they pure cestata, their offspring 
would multiply in time to become like the Vavii colony; were they mixed in gametic 
constitution, their descendants would segregate out into two or more class-types, 
