348 C. O. WHITMAN. 
low as 7°C. This fact shows that they still retain the hardi- 
ness characteristic of Leeches in general. 
In Japan the extremes of temperature mark a rather high 
amplitude; but they are not so far apart as in corresponding 
latitudes of the neighbouring continent. The surrounding sea 
and the Black Stream (Kuro-shiwo) are two important factors 
in determining the climate of Japan; besides giving a milder 
winter and a cooler summer than are found on the west side of 
the Japan Sea and the Yellow Sea, they keep the air abun- 
dantly supplied with moisture throughout the year. Some idea 
of the mildness of the winter at Tokio (354° N.), which lies 
nearly in the latitude of the localities from which Land Leeches 
have been obtained, may be gathered from the fact that chrysan- 
themums appear in October, camellias in December, plum- 
blossoms in February, and cherry-blossoms early in April. At 
Tokio the extremes of temperature seldom exceed —35° C. and 
—7°C. In the thickly wooded, elevated districts inhabited by 
Land Leeches, the winter temperature will often fall below +7°C., 
and the summer temperature will fall far below the temperature 
at the same season in Tokio. During the summer, the Japanese 
Land Leeches enjoy a moderately cool, moist, and veryfeven 
temperature; in winter they are often covered with snow, and 
undoubtedly undergo a winter sleep, as in some parts of the 
Himalayas. 
Their capacity for enduring a temperature considerably 
below the freezing point, their ability to live under water for 
at least several weeks, and their restriction to perennially moist 
climates, all show that they have not departed very far, physio- 
logically, from their aquatic predecessors. The untold ages 
required to scatter them in so many distant and isolated parts 
of the earth have sufficed to fix them in terrestrial habits of 
life; but this life has been offered to them under such easy 
conditions that they have been able to adopt it without 
fully surrendering their qualifications for the original mode 
of life. 
According to this view, the Land Leeches are not yet fully 
emancipated from the conditions of aquatic life, since they 
