PARTULA CLARA. 79 
ter may be recognized. It is significant, none the less, that the various colonies of 
marmorata differ so greatly, in localities which have been recently occupied by 
migrants from the old territory. 
But it is not justifiable to conclude that mutation can take place, or has taken 
place, only when a new locality is invaded. In several of the valleys originally 
inhabited by var. prima, banded forms occur that are peculiar, although of course 
they all agree in having the rotating stripes. The shells of Faarahi and Vaihiria 
(plate 21, figs. 13, 14, and 19 to 23) are sufficient to illustrate this point. Aside 
from the fact that ecological conditions are essentially similar in all parts of the 
island, wherefore it would be difficult or impossible to distinguish the environmental 
factors producing mutation when a species like clara emigrates to a new locality, 
it is significant that, under the conditions persisting in an old habitat, slight muta- 
tions may occur. 
VI. Partula clara must not be regarded as a newly arisen species, but as one which 
has recently revived after a long period of racial decline. Its nearest relatives are P. 
hyalina (of its own island and other groups), P. attenuata (of Tahiti and Raiatea), 
and P. annectens (of Huahine). ‘This congeries of forms is widely spread, and its 
members depart in their individual ways only slightly from the common qualities 
of all. While P. clara might have originated from P. attenuata in Tahiti, and not 
in Raiatea, this does not seem probable, because the latter species is narrowly 
restricted in its variations; P. hyalina is colorless and could scarcely have given rise 
to the colored varieties of P. clara. 
The general impression that deepens in the course of close studies like the fore- 
going has been well expressed by Pilsbry, in writing about the group including the 
four species enumerated, including Partula clara. He says (p. 179): 
“These forms may have exceptional means of distribution, or they may be conserva- 
tive stocks, which have altered little since the original radiation over the mountain ranges 
which are now islands. They approach the simply colored southwestern forms of Partula, 
such as those of the Solomon Islands, in appearance, and seem to be little changed members 
of an old stock.” 
There are no exceptional means of distribution at the service of these species; 
as for the rest, my own conclusions are in entire accord with those of Pilsbry. 
It is clear that in recent years Partula clara has entered upon a new period of vigor- 
ous increase, dispersal, and differentiation, after its long history of quiet, toward the 
end of which it seems to have been in imminent danger of extinction. 
