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Owing to the excessive roughness of the weather, our passage from Rio Janeiro to the Bay of Conception afforded us but few opportunities to add to our collections. A snipe blown out to sea from the Rio de la Plata, a specimen of Diomedea Albatros at Terra del Fuego, a large Salpa, and a Lepas, were all we were able to obtain. The Bay of Conception presents a rich field to the ornithologist.
But Mr Huxley shews, by observation and experiment on Salpa and Pyrosoma, that each has independent powers of reproduction, and his facts are conclusive against the theory of 'alternation of generations. The two generations, as now appears, are not of distinct individuals, but are both required to make a complete individual.
Secondly, a Salpa, of the class which lives apart and has fine long fibres projecting from the hinder part of the body. Thirdly, a small animal, nearly allied to the Diphyes, the soft part of the body, which contains the tube for receiving nourishment, having no air-bladder. Fourthly, a small Beroe, having the power of drawing in its fins. Fifthly, a very small Porpita.
This is in fact a true virgin reproduction, and directly comparable to the alternation of generations observed in the jelly fishes, in Salpa, and certain intestinal worms.
Besides these animals, six varieties of Pteropodes were caught; also a Glaucus, differing from that of the Atlantic Janthina penicephala Per., a Planaria, Salpa vivipara Per., a Pyrosoma, resembling that of the Atlantic, and a Lepas, attached to the shell of the Janthina. Our collection of Acalephi was extremely rich; of fourteen kinds taken, only one, Physalia Lamartinieri, was known to us.
By this is meant the following phenomenon: Certain animals, as the salpa and doliolum of the order of the tunicata, as well as certain mites and many tape-worms, produce offspring which are wholly dissimilar to the mother stock. The plant-lice transmit themselves through six, seven, even ten generations by means of sprouts, until a generation appears which lays eggs.
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