Page:Natural History, Mollusca.djvu/334

 motion resembling that of a serpent—the chain often extending to many feet in length—it is evident that this motion must arise from the unequal manner in which the different individuals act throughout the whole line. . ..

"I had occasion to remark of this animal, that, like the Medusæ and analogous tribes, it cannot bear to be confined in a limited portion of water, as it died, even in the ship's bucket, in less than half an hour—a very remarkable circumstance in the economy of these imperfect animals.

"Hitherto, this genus is only known as the inhabitant of hot climates, and of the Mediterranean Sea. I found it in great abundance in the harbours of Canna and Campbelltown, rising to the surface in calm weather, and crowding the water as the Medusæ often do at the same time of the year. . ..

"I was desirous of observing whether this animal, like many other of the marine worms, emitted light, but had no opportunity of ascertaining the fact, as they seemed always to retire to the bottom at sunset, and those which were taken on board died (as I have already observed), in a very short time."

The Pyrosomata are aggregated in another manner. They consist of lengthened individual Ascidians, united to each other at their basal part, and free at the opposite extremity, with their connexion so arranged as to compose numerous and regular rings, which concur to form a long, free cylinder, or tube, open at one extremity and closed at the other.

Cuvier states, that this great cylinder swims