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DESMOSCOLECIDA

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Originally appearing in Volume V08, Page 99 of the 1911 Encyclopedia Britannica.
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DESMOSCOLECIDA , a See also:

group of See also:minute marine See also:worm-like creatures. The See also:body tapers towards each end and is marked by a number of well-defined ridges. These ridges resemble on a small See also:scale those which surround the body of a Porocephalus (Linguatulida), and like them have no segmental significance. Their number varies in the different See also:species. The See also:head bears four setae, and some oI the ridges See also:bear a pair either dorsally or ventrally. The setae are movable. Two pigment spots between the See also:fourth and fifth ridges are regarded as eyes. The Desmoscolecida move by looping their bodies like geometrid caterpillars or leeches, as well as by creeping on their setae. The mouth is terminal, and leads into a See also:muscular See also:oesophagus which opens into a straight See also:intestine terminating in an anus, which is said to be dorsal in position. The sexes are distinct. The testis is single, and its duct opens into the intestine and is provided with two chitinous spicules. The ovary is also single, opening independently and anterior to the anus.

The See also:

nervous See also:system is as yet unknown. There are several species. D. minutus Clap. has been met with in the See also:English Channel. Others are D. nematoides Greef, D. adel phus Greef, D. chaetogaster Greef, D. elongatus Panceri, D. lanuginosa Panceri. Trichoderma oxycaud See also:alum Greef is o•3 mm. See also:long, and is also a " ringed creature with long See also:hair-like bristles." The male has two spicules, and there is some doubt as to whether it should be placed with the Desmoscolecida or with the See also:Nematoda. With regard to the systematic position of the group, it certainly comes nearest—especially in the structure of its reproductive organs—to the Nematoda. We still, however, are very ignorant of the See also:internal See also:anatomy of these forms, and until we know more it is impossible to arrive at a very definite conclusion as to their position in the See also:animal See also:kingdom. See Panceri, Atti See also:Ace. Napoli. vii. (1878) ; Greef, See also:Arch. Naturg. 35 (i.) (1869), p.

112. (A. E.

End of Article: DESMOSCOLECIDA

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