. Text-book of zoology for schools and colleges. Zoology. SCOLECIDA. 115 and the nervous system is in the form of a gangliated cord surrounding the gullet, and sending filaments backward. Among the best known of the parasitic Nematodes are the common round-worm {Ascaris lumbricoides) and the thread- worm ( Oxyuris) of the human subject, both of which inhabit the alimentary canal, and the guinea-worm {Filaria), which spends a portion of its existence in the cellular tissue of man, especially of the legs, and which attains a length of several feet. More dan- gerous than any of these is the Trieh
. Text-book of zoology for schools and colleges. Zoology. SCOLECIDA. 115 and the nervous system is in the form of a gangliated cord surrounding the gullet, and sending filaments backward. Among the best known of the parasitic Nematodes are the common round-worm {Ascaris lumbricoides) and the thread- worm ( Oxyuris) of the human subject, both of which inhabit the alimentary canal, and the guinea-worm {Filaria), which spends a portion of its existence in the cellular tissue of man, especially of the legs, and which attains a length of several feet. More dan- gerous than any of these is the Triehina, which spends its immature stages encysted in the muscles of some such animal as the pig, and only attains maturity and becomes capable of producing eggs, when in- troduced into the alimentary canal of some other warm-blooded verte- brate animal. When this takes place, a train of symptoms are originated which sometimes re- semble rheumatic fever, and appear to be very generally fatal. Of the free Nematode worms, which are never parasitic at any time of their lives, about two hun- dred species have been described, most of which inhabit fresh water or the shores of the sea. Qne of the most familiar is the so-called " vinegar - eel" {Anguillula aceti, Fig. A A).. Fig. 42.—Ncmatoda. A. Vinegar-eel {Angidllida aceti). B. Dorylai- mus stagnaUs, a free Nematode, living in stagnant water. Oedee VIII. RoTiPEEA (Lat. rota, wheel; fero, I carry).—The Motifera, or "wheel-animalcules," derive their popular name from the fact that the anterior end of the body is furnished with one or two circlets of cilia (Fig. 43) which, when in motion, vibrate so rapidly as to produce the illusory impression of a quickly-rotating toothed wheel. The Motifera are almost all aquatic, and are mostly inhabitants of fresh water. They are all microscopic in size, none attaining a greater length than one-thirty-sixth of an inch. In the females there is a distinct mouth, intestinal canal
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
