Page:Encyclopædia Britannica, Ninth Edition, v. 17.djvu/340

Rh 326 N E M N E M Classifi cation. of Qllulanus. The adult worm, which is of extremely minute size, the male being only -fatli an d the female of an inch in length, inhabits the alimentary canal of man and many other car nivorous mammalia ; the young bore their way into the tissues and become encysted in the muscles within the muscle-bundles ac cording to Leuckart, but in the connective tissue between them according to Chatin and others. The co-existence of the asexual encysted form and the sexually mature adult in the same host, ex ceptionally found in Ollulanus and other Kematodes, is the rule in Trichina ; many of the embryos, however, are extruded with the fieces, and complete the life cycle by reaching the alimentary canal of rats and swine which frequently devour human ordure. Swine become infested with Trichina in this way and also by eating the dead bodies of rats, and the parasite is conveyed to the body of mau along with the flesh of &quot; trichiuized &quot; swine. Bibliography. General Treatises : Cobbold, Entozoa (London, 1864) and Parasites (London, 1879); Leuckart, Die menschlichen Parasiten, vol. ii., Leipsic, 1876 ; Kiichenmeister, Die Parasiten des Menschen, Lf. 3, 2d ed., Leipsic. 1881 ; Chatin, La Trichine et la Trichinose, Paris, 1883. Systematic : Goeze, rersuch einer Satury. der Eingeweideiciirmer (Blankenburg, 1782), and Enter Nachtrag, &amp;lt;tc,, init Anmerk. von Zcder (Leipsic, 1800) ; Rudolph!, Entozoorum historia naturalis, Ams erdam, 1808 ; Dujardin, Histoire naturelle des helminthes, Paris, 1845; Diesing, Systema helminthvm, Vienna, 1850; Bastian, &quot;Monograph of AnguillulicUe,&quot; Trans. Linn. Soc., 1865; Biitschli, &quot;Beitrage zur Kenntn. d. freileb. Nematoden,&quot; Nov. Act. Acad. Leip., 1873, and &quot; Ueber freileb. Nematoden,&quot; Abh. Sent, naturf. Gesells. Frankfurt, 1874; Villot, &quot;Faune helminth, de la Bretagne,&quot; Arch. Zool. Exp., 1875; De Man, &quot;Onderz. over vrij in de Aarde levende Nematoden,&quot; Tijdsh. d. Nederland. Dierlc. Vereen, 1875 and 1876 ; V. Linstow, numerous papers in Arch. fiir. Naturg., 1872-83. Anatomy and Development : Besides the text-books of zoology, see Lubbock, &quot; Sphserularia bombi,&quot; Nat. Hist. Rev., 1S61 and 1864 ; Eberth, Unter- such. iiber Nematoden, Leipsic, 1863; Schneider, Monographic der Nematoden, Leipsic, 1866; Bastian, &quot;Anatomy and Physiology of Neinatoids,&quot; Phil. Trans., 1866; Villot, &quot;Monographic des Dragonneaux,&quot; Arch. Zool. Exp., 1874; Butschli, &quot;Zur Entwick. Geschichte des Cucullanus elegans,&quot; Zeitsch. wiss. Zool., 1876; Ercolani, &quot; Osservazioni sulla vita libera dell Ascaris maculosa,&quot; Mem. Ac. Sci. Bologna, 1877. Distribution : V. Linstow, Compendium der Helminthologie, Hanover, 1878. (F. E. B.) NEMEAN GAMES. See GAMES, vol. x. p. 65. NEMERTINES, or NEMEKTEANS (Nemertea), is the name of a subdivision of worms, 1 characterized by the ciliation of the skin, by the presence of a retractile pro boscis, by the simple arrangement of the generative apparatus, and in certain cases by a peculiar pelagic larval stage to which the name &quot; pilidium &quot; has been given. Many of them are long thread-shaped or ribbon-shaped animals, more or less cylindrical in transverse section. Even the comparatively shortest species and genera can always be termed elongate, the broadest and shortest of all being the parasitic Malacobddla and the pelagic Pelagonemertes. There are no exterior appendages of any kind. The colours are often very bright and varied. They live in the sea, some being common amongst the corals and algse, others hiding in the muddy or sandy bottom, and secreting gelatin ous tubes which ensheath the body along its whole length. Formerly, they were generally arranged amongst the Platyelminthes as a suborder in the order of the Turbel- larians, to which the name of Rhynchoccela was applied, the other suborders being the Dendrocoela and the Rlial)doccela. With the advance of our knowledge of these lower worms it has been found desirable to separate them from the Turbellarians and to look upon the Nemertea as a separate phylum of Platyelminthes. Lately the interest in their morphology has increased, since it has been advanced (6, 8) 2 that certain points in their organization appear to indicate a remote degree of relationship to the ancestral forms which must have preceded the Chordata (to which the vertebrate animals also belong), and that this relationship is closer than that which exists between those Protochvrdata and any other group of invertebrate animals. CLASSIFICATION. The Nemertines are subdivided into three suborders: Ifoplonemertea, Schizoncmertea, and P llxonemertea (5). The (1) Hoplonemertea embrace all the species with a stylet in the proboscis, and also Malacoldella, which has an unarmed proboscis, but which, by the details of its organization and its develop ment, must certainly be placed here (parasitism may be the cause of its incipient degeneration). The special characters of this suborder may be gathered from the anatomical descriptions hereafter to be given. In those species of which the embryology has been investigated the development was direct. The more common or more important genera are Ampliiporus (A. pulcher, British coasts, Mediterranean ; A. splendidus, Atlantic), which is comparatively short, N emeries (N. gracilis, Atlantic and Mediterranean ; JV. antonina, Mediterranean ; N. echinoder- ma, Mediterranean), which is long and thread-like, Tetra- stemma, Drepanophorus (with more complicate armature in the proboscis), Akrostomum, Malacobddla. (2) In the Schizonemertea all those genera and species are united which have deep, longitudinal, lateral, cephalic fissures. The development of some (Linens) is characterized by the so-called larva of Desor, of others (Cerelratulus) by the 1 Nemertes was a sea nymph, daughter of Nereus and Doris, of the g2nera was named Nemertes by Cuvier. One These figures refer to the bibliography at the end of the article. Fig. 1. Fig. 2. FIGS. 1, 2. Diagrams of the organs of a Xemertine, fig. 1 from below, fig. 2 from above, m, mouth ; div, intestinal diverticula; a, anus ; ov, ovaries ; n, neph- ridia; Br, brain-lobes ; In, longitudinal nerve stems ; pi; proboscis ; ps, pro boscidian sheath ; P.O., opening for proboscis. curious and characteristic pilidium-larva. The principal genera are Linens (L. longissimus, Atlantic ; L. obscurus), Cerebratuhis (C. marginatus, C. lilineatus, both Atlantic and Mediterranean ; C. vrticans, Mediterranean ; C. fascio- latiis and aurantiacus, C. hepaticus and dohrnii, Medi terranean; C. macintoshii, Madeira), Langia (L. formosa), Borlasia (B. elizabethsz). (3) Of the Palseonemertea the most typical and most characteristic genera are Cari- nella and Cephalothrix. They differ considerably both from Hoplo- and from Schizonemertines, and evidently belong to a lower stage of differentiation. The genera Polio, (P. delineate and P. curta, Mediterranean) and Valen- cinia are provisionally arranged in this order because, though less primitive, they are not typical representatives of the other two suborders. The development of these species is not at all, or only very superficially, known. For the further characters of the last two suborders see the anatomical description below. Another subdivision generally current is that into the Enopla and the Anopla (14). This does not, however, take into sufficient account the primitive and diverging