40 VARIATION, DISTRIBUTION, AND EVOLUTION OF THE GENUS PARTULA. 
serious; the immediate task is to deal with the snails of the Society Islands, for this 
region is now the headquarters of the whole genus, both as regards the variety of 
species and the abundance of individuals. 
In very few particulars does hyalina exhibit any peculiarities in its habits or 
its general ecological relations; these are essentially the same as in other Partule, 
already described in an earlier section. Like all other forms, during the day it 
usually remains sealed-up upon leaves or stalks of its habit-plants and crawls down 
to or near the ground at night for the purpose of feeding upon decaying vegetation. 
Sometimes during the day a heavy shower that drenches the vegetation of the 
valleys will cause the snails to resume activity, but the adults may not respond at 
all until the darkness of evening or night adds its accustomed influence. It does not 
seem to be necessary for the animals to be flooded by rain-water to bring about 
activity, during either day or night; primarily the rise of humidity in the former 
case and the absence of light in the latter acts as the stimulus to activity. Material 
brought to New York for observation in the laboratory displayed the same sen- 
sitiveness to moisture and dryness, light and darkness, which may be observed in 
the field. 
The favored nurse-plant varies in different valleys. In Fautaua the “fei” 
(Musa, plantain) and ’ape (Colocasia) are more apt to bear hyalina than the 
citrus or larger timber trees. When Dracena is in season, smaller snails are fre- 
quently found under its leaves. Wherever thickets of turmeric occur in a region 
inhabited by snails, they will furnish a higher proportion of hyalina than one can 
discover on the neighboring bushes and trees. But when all the observations are 
brought together there proves to be no single plant that is the universal favorite 
of this species of snails; the plaintain may be preferred in one valley, while in 
another place where this is equally abundant, other plants like the caladium will 
provide a richer collection of snails of this species. . 
One feature is worthy of note in view of certain considerations that will be 
stated in the subsequent general discussion of the occurrence of this species in 
limestone islands of the Cook Group. ‘This feature is the preference of the snails 
for more open situations in the several valley areas where they live. Often the 
first Partule met in entering a valley belonged to this species, while in places such 
as the borders of the streams, where larger forest trees are fewer and there is more 
sunlight, the hyalina would be found more frequently than in the deeper and wetter 
shaded areas. They are not confined to the open areas and to the drier borders of 
the whole region of Partula habitation, but seem to tolerate conditions that are not 
preferred, at least, by the representatives of P. otaheitana and other species. 
THE NUMERICAL DISTRIBUTION OF PARTULA HYALINA IN TAHITI AND ITS 
SIGNIFICANCE. 
In my collections Partula hyalina was obtained from 51 valleys and proved 
to be absent from 11 localities of the entire series of 62 stations which bore snails 
of this genus. Garrett described the species as “distributed in limited numbers 
throughout every valley in Tahiti’; undoubtedly he did not take into account the 
smaller valleys and gullies investigated in the course of the present research, which 
