DESMOSCOLECIDA

This article appears in Volume V08, Page 99 of the Encyclopedia Britannica.

Encyclopedia Britannica - Main :: DEM-DIO

DESMOSCOLECIDA , a group of minute marine worm-like creatures. The

body

BODY

tapers towards each end and is marked by a number of well-defined ridges. These ridges resemble on a small scale those which surround the

body

BODY

of a Porocephalus (Linguatulida), and like them have no segmental significance. Their number varies in the different species. The head bears four setae, and some oI the ridges

bear

a pair either dorsally or ventrally. The setae are movable. Two pigment spots between the 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 muscular oesophagus which opens into a straight

intestine

INTESTINE (Lat. intestinus, internal, usually in neuter plural intestina. from intus, within)

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

INTESTINE (Lat. intestinus, internal, usually in neuter plural intestina. from intus, within)

and is provided with two chitinous spicules. The ovary is also single, opening independently and anterior to the anus. The

nervous

NERVOUS

system

SYSTEM

is as yet unknown.
There are several species. D. minutus Clap. has been met with in the

English

ENGLISH

Channel. Others are D. nematoides Greef, D. adel phus Greef, D. chaetogaster Greef, D. elongatus Panceri, D. lanuginosa Panceri. Trichoderma oxycaud alum Greef is o3 mm.

long

LONG, GEORGE (1800-1879)
LONG, JOHN DAVIS (1838– )

, and is also a " ringed creature with

long

LONG, GEORGE (1800-1879)
LONG, JOHN DAVIS (1838– )

hair

HAIR (a word common to Teutonic languages)

-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 Nematoda. With regard to the systematic position of the group, it certainly comes nearestespecially in the structure of its reproductive organsto the Nematoda. We still, however, are very ignorant of the internal 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 animal kingdom.
See Panceri, Atti Ace. Napoli. vii. (1878) ; Greef, Arch. Naturg. 35 (i.) (1869), p. 112. (A. E. S.)

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