helping to keep the animal at the surface. Notwithstanding Rang's remark that the thread is doubtless formed of a special secretion, Eydoux and Souleyet think it probable that it consists merely of locomotory mucus, which, in these molluscs, may possibly possess special characters. Rang, it may be added, while examining spirit specimens, found, under the foot, a little glairy mass, which attached itself to the point of the scalpel, and was easily drawn out into a thread a foot and a half long; each specimen presented the same peculiarity, and Rang concluded that this was the substance from which the thread is made; it seems more probable, however, that the little masses were the remains of threads already spun, and perhaps reascended by the animal.
The above, the present writer believes, is all that is known of the spinning habits of Litiopa. These habits are certainly of a surprising character: the length of the apparently rapidly made thread, the animal's security upon it, and the facts that it can produce and afterwards ascend by it, not only in its native element, but also in the air, are points of special interest. As to the statements in the books, one may quote, for example, from Johnston's 'Introduction to Conchology':—
"The habits of the Litiopa are not less worthy of your notice. This is a small Snail, born amid the gulf-weed, where it is destined to pass the whole of its life. The foot, though rather narrow and short, is of the usual character, and, having no extra hold, the Snail is apt to be swept off its weed; but the accident is provided against, for the creature, like a Spider, spins a thread of the viscous fluid that exudes from the foot to check its downward fall, and enable it to regain the pristine site. But suppose the shock has severed their connexion, or that the Litiopa finds it necessary to remove, from a deficiency of food, to a richer pasture, the thread is still made available to recovery or removal. In its fall, accidental or purposed, an air-bubble is emitted, probably from the branchial cavity, which rises slowly through the water, and as the Snail has enveloped it with its slime, this is drawn out into threads as the bubble ascends; and now, having a buoy and ladder whereon to climb to the surface, it waits suspended until that bubble comes into contact with the weeds that everywhere float around!"[1]
- ↑ Johnston, 'Introduction to Conchology,' 1850, p, 134; with references to Rang and Kiener.
