Page:The Zoologist, 4th series, vol 4 (1900).djvu/345

Rh The speculations of Bélanger, it will be observed, here appear as statements of established facts, Johnston having been misled by Kiener, whose restatement of Bélanger's observations wants some of the precision of the original notes. Statements in other books (some adapted from Johnston) also exceed what is really known; and some are further objectionable from the fact that they do not make it clear that suspension is likely to be an occasional circumstance, not the usual condition under which the animal lives.

Alaba picta, a Litiopid found by A. Adams among Zostera in shallow water in the seas of Japan, is stated by him to spin a pellucid thread, with great rapidity, from a viscous secretion "emitted from a gland near the end of the tail"; it also creeps at the surface of the water, and, when fatigued, suspends itself, apex downwards, by means of the thread which is attached to the surface.

Valvata piscinalis (familiar in our ponds and canals) was observed to use a thread by Laurent. He noticed that the animals, in crawling at the surface of water, deposited there a trail of mucus, and that, when made to fall, some of them remained suspended to the floating trail by a thread; similarly, others were sustained in the water when forced to leave the branches of the plants on which they lived. In the former case some were seen to remount to the surface of the water by ascending their thread, which was gathered up by the foot. Mr. A.E. Boycott has written of the same animal, immature specimens of which, in captivity, were seen by him actively engaged in thread-spinning:—"Their usual mode of procedure was to crawl up the side of a glass vessel nearly to the surface of the water; they then gave one or two twisting motions, and crawled out on the under surface of the water, leaving a thread joining them to their point of departure. They then either sank slowly, remained floating, or sank about half way, where they stopped." The thread, the presence of which was easily demon-