. Animal biology. Zoology; Biology. Scrrcop/i Wuc/eas. Coni-rcrcti'/e part of ce/r nematos, thread, and eidos, form).— Either parasitic or free-living. 2. Gordiacea (gor di a' she a; L., gordius, referring to a complicated knot).—Parasitic in the larval stages and free-living and aquatic as adults. 3. Acanthocephala {'- alk'jG., akantha, thorn, and kephale, head).—All parasitic. 207. Free-living Nematodes.— Fig. 84.—a muscle cell from an ascaris. An inconceivably large number of These cells run longitudinally and are •^ " shown in cross section in big. 83. At the minute free-liv
. Animal biology. Zoology; Biology. Scrrcop/i Wuc/eas. Coni-rcrcti'/e part of ce/r nematos, thread, and eidos, form).— Either parasitic or free-living. 2. Gordiacea (gor di a' she a; L., gordius, referring to a complicated knot).—Parasitic in the larval stages and free-living and aquatic as adults. 3. Acanthocephala {'- alk'jG., akantha, thorn, and kephale, head).—All parasitic. 207. Free-living Nematodes.— Fig. 84.—a muscle cell from an ascaris. An inconceivably large number of These cells run longitudinally and are •^ " shown in cross section in big. 83. At the minute free-living threadw<jrms exist right are shown two sections of the same in the soil, in sand, mud, and debris from standing and running water, and in the sea. They are thus adapted to a great variety of hab- itats, are very resistant to drying and freezing, and are disseminated in numerous ways. The number of species is now believed to be very large, but to a great extent they are undoscribed. At the present time these free-living nematodes are often called nemas (Fig. 85). 208. Metabolism.—The food of roundworms is mostly fluid, being either blood or other juices from the host if the worm is a parasite; the juices of plants; or water containing microorganisms or organic matter in solution if the animal is free-living. This liquid food is pumped into the alimentary canal by the pharynx, is digested in the intestine, and is freely passed by absorption through the thin wall of the intestine into the body cavity. By means of this cavity it is distributed throughout the body. Within tissues it is passed from cell to cell. Kgestion takes cell to show how the appearances seen in Fig. 83 are produced. {The cell from Leuckart, "Parasilen des ;) The contractile part of the cell is indicated by lines, the non-contractile part by Please note that these images are extracted from scanned page images that may have been digitally enhanced for readabilit
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