PARTULA OTAHEITANA. I2I!I 
becomes more succulent, and the guava trees of the drier coastward parts diminish 
in numbers. At about 2 miles inland the valley divides, and above this point of 
division stands the sharp-pointed Pic de Francais, a characteristic example of the 
valley borders in this and other interior regions (plate 7b). Along the western 
branch the valley narrows and deepens vertically until it is a gorge of 700 to 800 
feet in depth, with abrupt walls that become sheer at the head of a canyon where 
the beautiful Falls of Fautaua pour from the inland extension of the valley. Above 
these falls the gradient becomes easier and finally the head-streams may be traced 
to their beginnings at the foot of “Venus’s Diadem,” a pinnacled rock that presents 
many of the features of the spine of Mont Pelée in Martinique. 
In my experience the Partule do not extend in any great numbers above the 
falls. They are most abundant on the lower levels about 33 to 4 miles inward from 
the shore. They occur on caladium and wild plantain with especial frequency; at 
times as many as 8 or 9 snails may be found on a single gigantic leaf of the former, 
snails that are dextral and reversed, light and dark in color, along with some indi- 
viduals of P. hyalina. ‘To all intents and purposes the area inhabited by P. otahei- 
tana otaheitana is compact, continuous, and well-populated. ‘The series of different 
years were taken from the same general locality, and probably not more than 2 
miles intervened between the most coastward and the most inland specimens. The 
importance of this fact for future discussion is self-evident. 
DESCRIPTION OF THE FAUTAUA SHELLS. 
The material in my own hands was secured in 1906, 1907, and 1908. In the 
first and second of these years many trips were made into Fautaua in order to study 
the conditions of temperature and humidity that affect the Partule, and hence the 
collections of those years are most satisfactory. The series of 1908 was obtained for 
me by Chief Mote. In that year, as well as in 1909, the greater part of the time of 
sojourn in the islands was employed in exploring other members of the Society 
Group, as well as Samoa, Tonga, etc. After discarding a few of the snails for 
one reason or another, such as mutilated condition, there remain 955 adults and 
396 adolescent individuals, while the former have furnished 1,182 young and eggs, 
of which over 500 were sufficiently advanced to give data relating to the heredity 
of color and of the coil of the shell. 
The adult shells of this colony present features that for convenience may be 
termed unit-characters, some of which are strictly alternative, while others exhibit 
fluctuations so as to merge into one another. These fall into three groups, as they 
are displayed in (1) the coil of the shell, (2) the color, and (3) the dimensions of the 
shell and of its parts. 
(1) In the coil the shells are either dextral or sinistral; of necessity no inter- 
mediate condition could exist. It will appear hereafter that the two types do not 
breed absolutely true, as Mayer was the first to point out, for sinistral young are 
produced by dextral adults and vice versa. But it is noteworthy (again as first 
established by Mayer) that the young contained in an adult at any one time are 
either all dextral or all sinistral, and may thus differ collectively from their parent. 
