70 VARIATION, DISTRIBUTION, AND EVOLUTION OF THE GENUS PARTULA. 
The fundamental statistics in the present connection are given for the entire 
collection of adult shells in the form of a complete census of the color-types (table 
29) with the numbers actually taken and the proper geographical assignments. 
What are regarded as the probable inter relationships of the color-classes and 
color-orders are shown in diagrammatic form in text-figure 4. 
marginata 
umicolor—hicolor—mitella 
nntella-rubra—phaea-rubra castane Pass Be vespera-rosea 
ane (SON og ime 
castanea-purpurea vespera-cyanea 
Fic. 4.—Partula gibba, Guam, probable interrelations of color classes and color-orders. 
At the very outset, it is evident that the color constitution of the several 
local series varies to an extraordinary degree. In very few places is there only a 
single color-type and, when this is the case, it is not always the same kind. The 
color components reach their highest number at Macajna second, where no less 
than eight occur. In addition, the relative numbers of the color-classes vary from 
locality to locality, thus accentuating the colonial differences as regards colora- 
tion. The several classes now to be described are not taken up in any geographical 
sequence, but on the basis of their own distinctive peculiarities, from the lightest 
and simplest to the darker and more complex. 
unicolor— This form is so named on account of its uniformity and simplicity 
(figs. 1 to 14, plate 12). It was found in abundance in two places, Tarague and Lolo, 
and it was consistently absent from all other stations, even where its close relative 
bicolor was present. The Tarague shells are corneous-yellow or straw-colored, 
varying somewhat from lighter to darker shades (figs. 1 to 4, 7, plate 12); in very 
few examples is the color darkened by an admixture of brown. The inner wall 
of the shell is similar to the outer (fig. 7, plate 12). In a considerable number the 
shell is greatly altered by decortication (figs. 5, 6, plate 12) and in the extreme cases 
it is virtually white with a dull surface, owing to the complete loss of the shining 
epidermis. ‘The adolescents are fully colored (fig. 8, plate 12) showing that decor- 
tication takes place, if at all, only when the animal reaches maturity. 
In sharp contrast with the Tarague shells, the unicolor of Lolo are pale cor- 
neous with only the slightest addition of yellow in exceptional individuals (fig. 
9 to 14, plate 12), yet the yellowest Lolo shell is still paler than the lightest Tarague 
specimen and there is no overlapping. The immature individuals of Lolo are 
consistently pallid like the adults (fig. 14, plate 12). In the first analysis of 
unicolor the two series in question were given distinctive ordinal names which 
referred to their respective stramineous and pallid shades of color; while these terms 
have been omitted for the sake of condensation, the distinctions require due 
emphasis, especially because associated classes of the two localities, notably 
mitella, also differ correspondingly. 
In the shells of both regions, the lip is predominantly white (see table 31, next 
section). As a final point, the white border below the suture varies greatly in 
width and distinctness, as the illustrations clearly demonstrate; in this respect 
