78 VARIATION, DISTRIBUTION, AND EVOLUTION OF THE GENUS PARTULA. 
its near neighbors, it will be seen that they also differ from the average to diverse 
degrees in the seven characters, and that the general course of deviation followed 
by one valley colony is independent of the mode pursued by another community. 
IV. The recent wide dispersal of clara seems to be the result of spontaneous active 
migration, and not of human transportation. ‘The question as to the mode of dis- 
persal has already been discussed in the case of marmorata, and little needs to be 
added. In spreading toward the west and north, this species has come to occupy 
valleys whose mouths are more than 10 miles from the opening of Tereehia Valley, 
which was probably the western limit in Garrett’s time; but the distance over the 
intervening ridges is far less. “The migration into valleys of the eastern quadrant 
also involves a much shorter distance than the coastal are of the eastern section 
beyond Maara and Apirimaue. To populate Taiarapu, however, the snails must 
have followed the low vegetation across the isthmus until the higher and more 
humid mountains were gained and traversed to the further sides. The passage of 
the ridge between Vaihiria (or Taharua) and the great basin of Papenoo Valley 
necessitates a journey of only a mile or so. ‘That the varieties of clara occurring 
in Papenoo are probably members of the prima series has already been shown. 
It is quite true that the snails of this and other species occur on plants that are 
sometimes transported by man. The fruit of the wild plantain (fei) of the interior 
regions is continually sought by the natives as a staple article of food. But the 
man goes into that valley which is nearest to his home, and any snails hidden ina 
bunch of plantains brought to the coast would undoubtedly die before they could 
return from the dry shore areas to the moist woods—f, indeed, they were not roasted 
along with the fruit. Very rarely plantains are taken from one valley for establish- 
ment, and only in such cases would there be a chance of passive dispersal of a species. 
One such instance has actually been discovered in the smaller island of Moorea. 
In Tahiti, however, very little transplanting has been done, and in such cases the 
distance involved is very short, owing to the sectional animosities of the local tribes. 
To take a concrete case, the small forms called minor and parva occur in a region 
whose natives are somewhat at odds with those of the original area where prima 
now occurs. It is not probable that the former types have been established in the 
districts of Punaauia and Paea through the carriage of Papara shells on vegetable 
foods. 
V. Mutation has taken place in some, but not in all, of the localities into which clara 
has migrated recently; but mutation 1s shown as well in parts of the former territory of 
occupation. ‘Vhe first point is sufficiently established by the paragraphs in the fore- 
going detailed description that deals with the banded types of Aoua and other 
valleys, and with the form-varieties in places occupied by var. marmorata. Only 
in the first-named cases, however, can the final criterion of mutation be employed, 
where the banded aberrant can be proved to produce similar banded offspring; 
in the case of marmorata, the mutants of large size can be designated as such with 
finality only when their young may be reared to a point where the parental charac- 
