THE LOB OS A 91 



Arcella is common in bogs and stagnant water, but is occasionally 

 found in clear running water. 



Pyxidicnla, Ehr., differs from Arcella in having a large gaping pylome. 

 The surface of the shell is ornamented with numerous minute tubercles. 

 20-50 /x. The genus is comparatively rare and little known. 



LITERATURE. 



1. Awerinzew, S. Die Structur und die chemische Zusammensetzung dcr 



Gehause bei den Siisswasserrhizopoden. Arch. Trot, viii., 1906, p. 95. 



2. Bott, K. Ueber die Fortpflanzung von Pelomyxa palustris. Arch. Prot. 



viii., 1906, p. 120. 



3. Bourne, A. <!. On Pelomyxa viridis n. sp. Q. J. Micr. Sci. xxxii., 1891, 



p. 357. 



4. Butschli, 0. Investigations on Microscopic Foams and on Protoplasm. 



Translated by E. A. Minchin. Black, 1894. 



5. Untersuchungen liber Structuren. 1898. 



6. Calkins, Gf. N. Marine Protozoa from Woods Hole. U.S. Fish. Comm. 



Bull. 1901, p. 413. 



7. Evidences of a Sexual Cycle in the Life-History of Amoeba proteus. 



Arch. Trot, v., 1904, p. 1. 



8. Frenzel, J. Untersuchungen iiber die mikroskopische Fauna Argentiniens. 



Arch. mikr. Anat. xxxviii., 1891, p. 1. 



9. Ueber einige merkwiirdige Protozoen Argentiniens. Zeitschr. wiss. 



Zool. liii., 1892, p. 334. 



10. Goldschmidt, . Die Chromidien bei Protozoen. Arch. Prot. v., 1904, 



p. 126. 



11. Hertwig, A*. Ueber Encystirung und Kernvermehrung bei Arcella vulgaris. 



Fest. Kupffer, 1899. 



12. Ijima. New Rhizopod of Man. Annot. Zool. Jap. 1898, p. 85. 



13. Jennings, H. S. Contributions to the Study of the Behaviour of the 



Lower Organisms. Washington, 1904. 



14. The Movements and Reactions of Amoeba. Biol. Centralbl. xxv., 



1905, p. 92. 



15. Leydcn, E., and Schaudinn, F. Leydenia gemmipara. S.-B. Akad. Berlin, 



vi., 1896. 



16. Martini. N. Beobachtungen an Arcella vulgaris. Zeitschr. wiss. Zool. 



Ixxix., 1905, p. 574. 



17. Mesnil, Ftlix. Chromidies et questions connexes. Bull. lust. Pasteur, 



iii., 1905, p. 313. 



18. Nereshcinier, E. Ueber vegetative Kernveranderungen bei Amoeba. Arch. 



Prot. vi., 1905, p. 147. 



19. Penard, E. Faune rhizopodique du bassin de Leman. 1902. 



20. Amibes a pellicule. Arch. Prot. vi., 1905, p. 296. 



21. Potent, W. Leidy's genus Ouramoeba. Science, viii., 1898, p. 778. 



22. Rhumbler, L. Beitriige ziir Kenntniss der Rhizopoden. Zeitschr. wiss. 



Zool. Hi., 1891 ; and same journal, Ixi., 1896. 



23. Zur Theorie der Oberflaclienkrafte der Amoeben. Zeitschr. wiss. 



Zool. Ixxxiii., 1905, p. 1. 



