Page:Natural History, Mollusca.djvu/335

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323
SWIMMING ASCIDIANS.

in the sea by means of the combined contractions and dilatations of all the individual animals which compose it. The branchial orifices are pierced near the points, and the anus opens into the interior cavity of the tube. Thus, says Cuvier, one may compare a Pyrosoma to a great number of stars of Botrylli, strung one after the other, but the whole of which would be moveable.

Mr. George Bennett, in his interesting "Wanderings in New South Wales," after some valuable remarks on the luminosity of the ocean, proceeds as follows:—

"On the 8th of June, being then in latitude 30' south, and longitude 27° 5' west, having fine weather and a fresh south-easterly trade-wind, and the range of the thermometer being from 78° to 84°, late at night, the mate of the watch came and called me to witness a very unusual appearance in the water, which he, on first seeing it, considered to be breakers. On arriving upon the deck, this was found to be a very broad and extensive sheet of phosphorescence, extending in a direction from east to west, as far as the eye could reach. The luminosity was confined to the range of animals in this shoal, for there was no similar light in any other direction. I immediately cast the towing-net over the stern of the ship, as we approached nearer the luminous streak, to ascertain the cause of this extraordinary and so limited phenomenon. The ship soon cleaved through the brilliant mass, from which, by the disturbance, strong flashes of light were emitted; and the shoal, judging from the time the vessel took in passing through the mass, may have been a mile in breadth. The passage of the vessel through them increased the