PARTULA OTAHEITANA. 123 
combinations of characters or fluctuations of these in order to define the complex of 
heritable qualities possessed by the colony as a whole. 
We may now pass to the consideration of the inter-relationships of the different 
component classes of the Fautaua colony, in sufficient detail to ascertain: (1) 
whether the two classes of sinistral and dextral shells are materially different; 
(2a) whether the banded individuals constitute an independent stock or are sporadic 
products of the plain group; and (2) whether the four principal color-classes are 
statistically different. 
COMPARISON OF SINISTRAL AND DEXTRAL SHELLS. 
NuMERICAL RELATIONS. 
The numerical relations of the dextral and reversed individuals in my collec- 
tions are not the same in successive years. For obvious reasons the series of 1906 
and 1907 are more important than the last lot, which comprised a larger proportion 
of adolescent snails of nearly full growth. ‘The detailed figures are given in table 57, 
TaBie 57.—Partula otaheitana otaheitana, Fautaua Valley. Numerical 
relations of the form-classes. 
Adults. Adolescents. Adults and Embryonic 
adolescents. young. 
No. /|Per cent.| No. |Per cent.| No. |Per cent.| No. /|Per cent. 
LOOS HSIN. EAs otal eaves 64 50.7 27 54.0 91 LY 51 51.0 
Gls: Suen boben Domo oo ane 62 49.2 23 46.0 85 48.2 49 49.0 
POO TASIN A Stilo stds ta di cree 230 56.6 92 52.2 322 Som 117 47.9 
COXA packotnsive-ciisiste maeiees 176 43.3 84 47.7 260 44.8 127 52.0 
ONG; Giigscoosonuwocoenooc 229 54.5 85 50.0 314 53.2 85 50.0 
COX Prah ten Vays oy terrenete tons 191 45.4 85 50.0 276 46.7 85 50.0 
1906-1908, sin............. 523 54.9 204 51.5 727 53.9 253 49.2 
ext. Ae. 429 45.0 192 48.4 621 46.0 261 50.7 
1899, Mayer, sin........... 54 64 55.6 
Gexe ection saen 46 51 44.3 
1870-1885, Garrett, sin...... oe 33 
dex an 66+ 
together with the data of Garrett and Mayer; they indicate that the relative num- 
ber of sinistral snails is diminishing after a long period of increase. Specifically, the 
original statement of Garrett is that “about one-third of the shells are sinistral’’; 
the period of observation can safely be given as between 1870 and 1885, although 
Garrett’s first sojourn in the island was from 1860 to 1863. Mayer found in 1899 
that the reversed shells amounted to 54 per cent in an ofaheitana collection of 138 
individuals from this valley, while the young dissected out of the adults of both 
form-classes showed a slightly higher percentage of the same coil, 64 per cent; 
hence a great relative increase of sinistral individuals must have taken place sub- 
sequent to Garrett’s studies. In 1906 the adults were in about the same condition 
as in Mayer’s time, but both the adolescents and the embryonic young of this coil 
have dropped to 50 per cent. ‘The effect of this reduction would not be manifested 
in the adult population until at least a year had elapsed, so that the 1907 shells 
would be less significant than those of 1908. The full-grown snails of this last year 
