swallowed by a mammal it develops, and the ordinary form is found in the excreta.
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Fig. 7.—Filosa and Foraminifera of similar habit. 1. Diplophrys archeri (moor pools); a, nucleus; b, contractile vacuoles; c, oil drop. 2. Allogromia fluviatilis (freshwater Foraminifer); a, numerous nuclei; the elongated bodies are ingested diatoms. 3. Shepheardella taeniformis (marine Foraminifer), with retracted protoplasm; a, nucleus. 4. The same with expanded pseudopods. 5-9. Nucleus of same in various aspects as carried along in streaming protoplasm. 10. Amphitrema wrightianum (moor pools); shell membranous, encrusted with foreign bodies. 11. Diaphorodon mobile (moor pools); a, nucleus. |
Centropyxis aculeata is closely allied to Diffugia. It divides by fission and also at the end of a cycle by schizogony, the offspring being amoebulae. In some these acquire a shell directly; in others a second brood division into four takes place, and it is only then that shells are formed. The latter conjugate as males with the former as females; and the fusion cell encysts within the approximated shells; it emerges as a naked amoeba after a period of rest, forms a shell and assumes the type of the species. Other types of reproduction are known, Amoeba coli, an inhabitant of the gut of man, showing an endogamous pairing of closely related nuclei similar to that of Actinosphaerium (see Heliozoa).
Classification
Lobosa.—W. B. Carpenter. Cytoplasm with a clear ectosarc, not wetted by the medium; pseudo pods never finely branching, usually rounded at the apex; nucleus single or multiple; shell (“test,” “theca”) absent, gelatinous, membranous or of cemented granules of ingested sand, &c., or plates secreted in the endosarc.
Selected genera: § 1. Naked Amoeba (q.v.) (“Amibe,” Bory), with the subgenera Dactylosphaerium, Hertwig and Lesser (fig. 1, 1-3), with slender, pointed pseudopods; Lithamoeba, Lankester, always containing inorganic granules (fig. 2). Pelomyxa, Greeff (fig. 1, 5, 6), with blunt, eruptive pseudopods and numerous nuclei, 112 in. or more in diameter when contracted. Arcuothrix, Claparède and Lachmann, with one or more slender, very mobile, flagelliform pseudopods as well as the lobose ones.
§ 2. Test gelatinous, perforated by pseudopods: Amphizonella, Greeff; Trichosphaerium, Schneider (fig. 5).
§ 3. Test membranous: Cochliopodium, Hertwig and Lesser (fig. 1, 8).
§ 4. Test “chitinous,” shagreened: Arcella, Stein (fig. 1, 7).
§ 5. Test of ingested particles: Diffugia, Leclerc; Centropyxis, Stein; Lecqueureuxia, Schlumberger (shell material of diatomaceous tests fused into sausage-shaped masses).
§ 6. Test of secreted siliceous or chitinous plates: Quadrula, F. E. Schultze. (In Q. irregularis the plates are said to be calcareous.)
Filosa.—A. Lang. Cytoplasm without definite ectosarc; pseudopods branching, tapering to fine tips, somewhat granular; test present in all known species and varying as in the Lobosa.
Selected genera: § 1. Test membranous: Gromia, Dujardin (pro parte); Mikrogromia, Hertwig; Diplophrys, Barker (fig. 7, 1); Ditrema, Archer; Amphitrema, Archer (fig. 7, 11); the last three have a mouth-like aperture (pylome) at either end of the test.
§ 2. Test of ingested or incrusted particles: Pseudodiffugia, Schlumberger; Diaphorodon, Archer (fig. 7, 12).
§ 3. Test of secreted plates: Euglypha, Dujardin (figs. 4, 6, A); sphenoderia lenta (fig. 6, B); Paulinetta, Lauterborn.
Bibliography.—E. Penard, Faune rhizopodique du bassin du Léman (1902), and Les Rhizopodes des grands lacs (1905); James Cash, The British Freshwater Rhizopoda and Heliozoa (Ray Society), vol. 1. (1905)—these works contain full bibliographies of older literature. L. Rhumbler, “Beiträge zur Kenntniss der Rhizopoden” (Zeitsch. Wiss. Zoologie, lii. (1891), and numerous papers in Arch. Entwickelungsgeschichte and Arch. Protistenkunde; F. Schaudinn, “Untersuch. üb. die Fortpflanzung einiger Rhizopoden.” in Arb. Kaiserl. Gesundheitsamt, xix. (1903); S. Awerinzew, “Die chemische Zusammensetzung der Gehäuse der süsswasserrhizopoden,” Arch. Prot. viii. (1906); K. Boll, “Über die Fortpflanzung von Pelomyxa palustris,” Arch. Prot. viii. (1906). For bibliographies and a clear exposition we may also cite Y. Delage and, E. Hérouard, Traité de zoologie concrète, i. (La cellule et les proiozoaires) (1896); A. Lang, Lehrb. d. vergleich. Anatomie d. wirbellosen Thiere (ed. 2), i., “Protozoa” (1901); and Marcus Hartog, “Protozoa,” in Cambridge Natural History, i. (1906). Of the older literature we need only cite F. Dujardin, “Sur les organismes inférieurs,” Ann. Sc. Nat. Zool. iv. (1835), and “Zoophytes, infusoires” (1841). (M. Ha.)
RHODE ISLAND, a North Atlantic state of the American Union, belonging to the New England group, and lying between 41° 18′ and 42° 3′ N. lat. and 71° 8′ and 71° 53′ W. long.[1] It is bounded, N. and E., by the state of Massachusetts; S., by the Atlantic Ocean; and W., by the state of Connecticut, from which it is separated in part by the Pawcatuck river. Rhode Island is the smallest state in the Union, having an extreme length, N. and S., of 48 m., an extreme width, E. and W., of 37 m., and a total area of 1248 sq. m., of which 181 sq. m. are water-surface.
Topography.—The region of which Rhode Island is a part was at one time worn down to a gently rolling plain near sea-level, but has since been uplifted and somewhat dissected by stream action. As a result the topography is characterized by low, rounded hills, but is nowhere mountainous. Since the uplift and stream dissection a slight depression has allowed the sea to invade the lower portions of the river valleys, forming the bays known as Narragansett Bay, Providence “river,” Sakonnet “river,” &c. Glaciation has disturbed the river
- ↑ Block Island, over which the jurisdiction of the state extends, lies 10 m. off the coast, and is not included within these limits.
