PARTULA OTAHEITANA. 167 
example from Apirimaue—it has seemed best to consider consecutively the colonies 
on the north and east before taking up the Oopu shells. 
It is a fortunate circumstance that the collection from this valley comprises a 
full series of individuals that are at the same time the largest and most beautiful 
specimens obtained in Tahiti. It consists of 272 adults and 95 adolescents, while 
the number of advanced embryonic young dissected out of the former amount 
to 267. 
Classifying the material on the basis of color, each of the two primary divisions 
of yellow and red shells may be still further divided (table 110). Whitish-yellow 
individuals form Group I (plate 28, figs. 3 and 4), and amount to about 7 per cent of 
all; no adolescent shells were of this color, and no embryonic shell was light enough to 
be assigned to this group; hence the attenuation of the yellow is something that 
comes about in later life. Among these shells, about two-thirds have the spire 
deeply tinged with purple—Section Is (fig. 4) as distinguished from Ia. The purer 
vellow shells form Group II (plate 28, figs. 5 to 7), with light-spired (fig. 5) and dark- 
spired members (figs. 6 and 7) in the proportion of 3 to 5; the adults of this group con- 
stitute 30 per cent of their respective series. When Groups I and II are combined, 
the percentages for the three growth-periods become more alike. Group III con- 
sists of reddish-orange shells (plate 28, figs. 8 to 10) occurring in small numbers in all 
three series, and with only half of the adults displaying the dark spire (figs. 9 and 10). 
The more characteristic red shells number over half of all, and in their division— 
Group IV (plate 28, figs. 13 to 17)—the purple-spired specimens (figs. 12 and 14 to 
17) are 6 times as numerous as the others. 
TasBLe 110.—Partula otaheitana rubescens, Oopu Valley. Numerical relations. 
No. of No. of 
adults, adults, 
plain tinged 
spire, A.| spire, B. 
Total No. of No. of Per cent | Per cent of} Per cent of 
of adult | adolescent | embryonic 
Nios G? || edlliez || CRA 
adults. cents. 
Color-class. 
Yellow, I, II 
Red, III, IV 
The partly grown shells (plate 28, figs. 19 to 22) are separable into the same color- 
groups, whose relative numbers do not agree perfectly with those of the adult 
divisions only because the total number of adolescents was far smaller, and not 
fully representative of the population at large. The embryonic shells (plate 28, 
figs. 18a to 18E)display the distinctive colors very early. 
The statistical analysis of the colony (table 111) brings out the primary fact 
that the four color-divisions exhibit considerable diversity. None of them is con- 
sistently different from another in the whole group of absolute measurements, or in 
the group of proportionate measures. Combining the red-tipped shells into one 
