PARTULA OTAHEITANA. 149 
Pirai association. However, because the times of collection could not be made 
equal in length and because also the meteorological conditions differed, the figures 
are approximate, even if not final, descriptions of the abundance of amabilis as it 
exists in the sector of its range. The second or averaged figure for each character 
has a biological significance of another kind, because each valley colony constitutes 
a complex with its own hereditary qualities; the general average of the four valley 
types recognizes an equal value of these types, irrespective of the abundance or 
paucity of its representatives in any one case. Both modes of viewing the summar- 
ized facts will be important in our final summary. 
TasLeE 88.—Partula otaheitana otaheitana and P. 0. amabilis. Statistical comparison. 
Mean value. Standard deviation. 
Character. ban aie 
Fu o. amabilis P. otaheitana | P. o. amabilis B. 0. amabilis 
average of otaheitana. combined. average of 
valley types. valley types. 
P. otaheitana | P. o. amabilis 
otaheitana. combined. 
Shell length, mm 19.1003 + .0208} 18.0018+.0151 17.9042 0.8961 .0189} 0.9885 + .0107 
10.9888 + .0142} 10.5839+.0076 10.5555 4768+ .0100] .4952+.0054 
proportions, p. ct... .] 57.4373 .0719] 58.7547 = .0368 58.9174 2.4049 + .0508) 2.4085 + .0260 
Aperture length, mm 9.8321+.0142] 9.3931+.0078 9.3724 4769+ .0100} .5107+.0055 
7.7239 .0115| 7.3152+.0065 7.3006 -3845 + .0081| .4282+.0046 
proportions, p. ct. | 78.4744+.0818] 77.8426+.0435 77.8371 2.7369 + .0579| 2.8482 + .0306 
Length aperture+length 
shell, proportions, p. ct...] 51.4076+.0590] 52.0881 + .0293 52.2466 1.9737 + .0417| 1.9171+.0207 
Tooth, index 2.7138+.0267| 2.8292+.0122 2.8175 -9069=+.0189| .7936+.0086 
P. o. otaheitana (sinistral), » =509 (tooth 524). P. 0. amabilis (sinistral), m =1947 (tooth 1909). 
PARTULA OTAHEITANA RUBESCENS Reeve. 
GENERAL CONSIDERATIONS. 
Beyond the range of the primary variety just described, the territory beginning 
with the valley of Tuauru is inhabited by two distinct subdivisions of P. otaheitana. 
One of these comprises the large sinistral forms of considerable beauty that were 
described under the name of Partula rubescens by Reeve in 1850; to this same variety 
must be referred the shells distinguished and distributed by Pease as Partula tur- 
ricula. The other variety, Partula otaheitana affinis, accompanies rubescens in 
nearly, but not quite, all of its valleys throughout the eastern part of Tahiti nui and 
Taiarapu as far as Apirimaue, in the southeastern district of Papeari. 
Such being the general situation, the problem dealing with the factorial value 
of the environment may be attacked with more confidence than heretofore, inasmuch 
as two entirely distinct groups of variants exist wnder identical conditions in the same 
valleys; they do not interbreed, as the ample evidence attests, and neither of them 
can be regarded as ancestral to the other, but each is derivable from a basic complex 
similar to P. otaheitana otaheitana as it exists in Fautaua Valley at the present time. 
Therefore the relations of these two series—rubescens and affinis—are essentially 
different from those obtaining between the light and dark, the plain and colored, or 
the direct and reversed snails that constitute an amabilis colony such as the associ- 
