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Kelaart has given descriptions of fifteen species of planaria, and four of a new genus, instituted by him for the reception of those differing from the normal kinds by some peculiarities which they exhibit in common. At Point Pedro, Mr. Edgar Layard met with one on the bark of trees, after heavy rain, which would appear to belong to the subgenus geoplana. Acalephæ.
Particles of matter fitted by digestion, and their transmission through a living body, for immediate assimilation with it, or flakes of lymph detached from surfaces already organized, seem neither to exceed nor fall below that simplicity of structure which favours this wonderful development; and the supposition that, like morsels of a planaria, they may also, when retained in contact with living parts, and in other favourable circumstances, continue to live and be gradually changed into creatures of analogous conformation, is surely not so absurd as to be brought into comparison with the Metamorphoses of Ovid.
The existence of a division of the genus Planaria, which inhabits the dry land, interested me much. These animals are of so simple a structure, that Cuvier has arranged them with the intestinal worms, though never found within the bodies of other animals.
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.
Of Mollusca we observed, a Limacina; two Eolidiæ, some of which have very beautiful colours; a Laniogerus; a Polycera; four kinds of Doris; a Scyllæa; an animal which deserves the name of Planaria, it was three inches long, two broad, and only half a line thick; on the upper surface, half an inch from the edge, are two projecting eyes; and in the same part, on the surface beneath, the mouth may be perceived; in the middle of this under surface is another aperture, from which the animal, when in a tranquil state, frequently strecthes out four small folds of skin; this creature, like the Planariæ, crawls very nimbly.
The worm is of a whitish colour, sometimes inclining to brown. Its thickness is from a half to two-thirds of a line, and its length has sometimes reached to ten or twelve feet. Small specimens have been found beneath the tunica conjunctiva of the eye; and one species of the same genus of Nematoidea infests the cavity of the eye itself. Planaria. In the journal already mentioned, Dr.
The existence of a division of the genus Planaria, which inhabits the dry land, interested me much. These animals are of so simple a structure, that Cuvier has arranged them with the intestinal worms, though never found within the bodies of other animals.
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