Page:Natural History, Mollusca.djvu/30

18 air. While it remains dry, it will float the animal, which then glides along as if on a solid body, crawling in fact, on the inferior surface of the air: but if by any agitation of the water, or by the will of the animal, the foot become overflowed, the state of suspension is ended, and the creature falls to the



bottom. The Pond-snails (Limneus), with olive-coloured fragile shells, that inhabit every little pool and lakelet, may be seen in a summer's day, by scores, enjoying the air in this manner.

The wide ocean between the tropics is inhabited