A large number of specimens of a species are usually found together, since their only mode of spreading is during the ciliated larval stage, which although it swims vigorously can only cover a few millimetres an hour; still it may be carried some little distance by currents.
At Caracas the annual rainfall ranged from 602 to 863 millimetres between 1894 and 1902.
A little vapour is given off at ordinary temperatures and pressures, and when under a few millimetres pressure only it rapidly vaporizes below Ioo° C. The freezing-point is uncertain, owing perhaps to the existence of two modifications, as suggested by Kast (Zeits.
Hence 1000Ã† is the elongation in millimetres per metre length per kilo.
The length of the body, exclusive of the proboscis, which measures about a line to a line and a half, varies according to the species from 6 or 8 millimetres in the case of G.