. A catalogue of the British non-parasitical worms in the collection of the British Museum. Worms. 82 ANNELIDES. Lost portions are restored with facility. A few secrete a luminous fluid, but an organ appropriated to the secretion has not been demon- strated. The skin is very generally margaritaceous or iridescent; and this is occasionally the case also with the bristles. 1. General Form.—The Annelides have an elongated worm-like figure, which, in some genera, inclines more or less to an oblong or No. a. Animal. b. Head. e. Jaws. d. Rings. oval. TheNereides oifer examples of the vermiform
. A catalogue of the British non-parasitical worms in the collection of the British Museum. Worms. 82 ANNELIDES. Lost portions are restored with facility. A few secrete a luminous fluid, but an organ appropriated to the secretion has not been demon- strated. The skin is very generally margaritaceous or iridescent; and this is occasionally the case also with the bristles. 1. General Form.—The Annelides have an elongated worm-like figure, which, in some genera, inclines more or less to an oblong or No. a. Animal. b. Head. e. Jaws. d. Rings. oval. TheNereides oifer examples of the vermiform species (); the Polynoc, and, more especially, the Aphrodites, may be instanced as examples of the latter. The length is often considerable. On our shores species are to be found nearly two feet in length, and as thick as the barrel of a large quill; but in equatorial seas some attain the length of five feet with a diameter of thirteen lines. 2. Body.—The body is composed of narrow segments or rings (No. VI. fig. d), not calcareous nor even corneous as they are in the great majority of Crustacea and insects, but membranous, and merely separated by a fold of still thinner membrane, such as we observe in many larvae and caterpillars, so that it is occasionally difficult to mark their exact limits. The number of the rings is in general very considerable, and proportionate to the length of the body, for the growth of this in length depends much more on the production of new segments than on the development of any one in particular. There are great diff'erences in the number of rings necessary to com- plete maturity. In some Polynoc there are not more than from 20 to 30 rings; in Phyllodoce lamellata not less than 500. In the species which have few rings, as in Aphrodite and Polynoe, the number appears to be specifically limited, and the same in all the individuals; but in the Nereides and others nothing is more variable, and less to be relied upon as a discriminative char
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Keywords: ., bookcentury1800, bookdecade1860, booksubjectworms, bookyear1865
