PARTULA OTAHEITANA. 247 
valley. Indeed, affinis exists in five valleys in company with sinistrorsa, and it 
would be impossible to attribute the origin of two distinct primary varieties to one 
and the same group of extraneous influences. The color-classes apex and phea do 
not occur everywhere; dextral mutants appear in numbers in three successive val- 
leys, and then they disappear, to recur in Faarahi and again in Taharua. In these 
cases, also, it is not reasonable to attribute the positive presence of a type to a cause 
other than a congenital one. 
Il. The average dimensions and proportions of the shells vary from valley to valley, 
without any consistent relation to environmental influences or to geographical sequence. 
Disregarding the dextral elements in certain specified cases, the figures for the 
sinistral colonies are given serially in table 192, while the differences with their 
probable errors are enumerated in table 193. The graphic presentation (table 194) 
gives the ranges of the several characters, in the whole series of valleys, as well as 
the averages and the fluctuations of the latter in geographical order. The Taiarapu 
colonies are made up of very large shells on the average; but rainfall and humidity, 
TaBLeE 192.—Partula otaheitana sinistrorsa. 
Colonial statistics of sinistral shells. 
Mean value. 
Shell. Aperture. Length aper- 
Valley. No. ae Geena Tooth, index. 
Length. Width. Proportions. Length. Width. Proportions. tions. 
a eee eos 
mm. mm. p. ct. mm. mm. p. ct. p. ct. 
Walaaiays ec 137) 20.1237 .0430) 11.2212 .0260) 55.6679+.1183) 10.4328 .0257) 7.8255+.0212) 74.9818+=.1519) 51.8212 .0962| 1 +.0 
Aiavaro...... 168) 20.1250=.0483) 11.0750+.0224) 55.0595+.1090) 10.1202+.0261| 7.6655+.0202| 75.6905 +.1351| 50.3036 .0889) 1 = .0 
Wenntic o6occece 219) 21.3979+ .0428) 11.4416+.0236) 53.4315+.1030) 10.6507+.0229| 7.8927 = .0188) 74.0936 .1120| 49.7466 .0762) 1 = .0 
Wiaipoerrrey- 3: 190) 21.8111 .0483) 11.4558+.0242| 52.4106+.1070| 10.7894+.0276| 7.8915+.0207| 73.0474 .1242) 49.4000 .0867)| 1 +.0 
Apirimaue. ...| 284| 19.3926 .0371| 10.6993 .0200) 55.1021+.0953) 9.6042 .0198) 7.1810+.0152) 74.7958 .1080) 49.4014 .0737) 1. +.0 
MRItAVATI ncn ler 165| 19.7500+.0483} 10.9073 +.0264) 55.1697 + .1426) 10.1267+.0249| 7.5715+.0215| 74.7788 .1629) 51.2636+.0991| 1.0774 .0188 
Tenaire...... 364! 19.1033 =.0338] 10.6813+.0162| 55.8406+.0874| 9.8242+.0180) 7.4522+.0136) 75.8956+.0932) 51.3599 .0688) 1.0296+.0065 
IWMiaararnlyeyee 132) 18.0045 = .0473) 10.3091+.0264) 57.1212+.1381) 9.1276+.0284) 7.0727+.0214| 77.4697+.1704) 50.7121+.1124) 1.1052+.0193 
Vaihiria...... 303) 18.2738 .0300} 10.2314+.0154| 55.9455 .0813) 9.2399+.0157| 7.0881 .0120) 76.5792+.0970| 50.4934 .0668) 1. = .0 
Vairaharaha. .| 247) 18.0949 .0325] 10.1202+.0174| 55.8887+.0900| 9.2539+.0191) 7.0506 .0139| 75.9818 .1085| 51.0830=+.0741| 1. + .0 
Faarahi...... 461] 20.1025+.0333) 11.0046+.0181] 54.6996+.0704) 10.0805 .0184) 7.6718 .0143| 76.0813 .0828| 50.0662+ .0601) 1.0903 + .0109 
Moaroa...... 432) 18.6424+.0261) 10.3352+.0127| 55.3750+.0721| 9.4583+.0138) 7.2218+.0107| 76.3171+.0793) 50.6968 .0579)| 1.3157+.0191 
Taharua......| 320) 18.5684=.0287) 10.3606+.0153) 55.7469+.0752) 9.4913+.0180) 7.2188+.0138) 75.9094+.1028) 51.0313 .0660) 1.3571+.0235 
which favor growth, are no greater there than in the districts of Mataiea and 
Papeari, where the shells are smaller. In the southern sector the size fluctuates as 
one passes westward, without any relation to the size of the valley, differences in 
vegetation, etc. Likewise the proportionate measures vary inconsistently. Pass- 
ing from Apirimaue to Titaviri, the shells become longer, the apertures increase in 
length, and the latter become far longer within reference tothe former; but in the pass- 
age from Vairaharaha to Faarahi, where shell-length and aperture-length increase as 
before, the proportionate figure diminishes. Local variations in the degree of the 
tooth development are even less attributable to anything but congenital influences. 
Ill. [t 1s tmpossible to determine whether the colonies of Taiarapu have been 
founded by migrants from Tahiti nut, or by snails introduced on vegetation carried by 
human beings. ‘The prior point is that sznistrorsa was formerly absent from the 
peninsula, for which the evidence has been given. It is true that on rare occasions 
