. Bulletin - United States National Museum. Science. 116 BULLETIN 120, UNITED STATES NATIONAL MUSEUM. animal turns over and presents itself edge on, it is seen to be very thin as compared with its breadth [fig. 81, c], and in section would appear flat or oval. Metcalf [1909] divides Opalinae into the following groups: (1) Species with two nuclei, bodies circular in cross section. (2) Species with many nuclei, body circular or broadly oval in cross section. (3) Species with many nuclei, body flattened. To these we may now add (4) Species with two nuclei, body flattened. The nuclei measure 20m a
. Bulletin - United States National Museum. Science. 116 BULLETIN 120, UNITED STATES NATIONAL MUSEUM. animal turns over and presents itself edge on, it is seen to be very thin as compared with its breadth [fig. 81, c], and in section would appear flat or oval. Metcalf [1909] divides Opalinae into the following groups: (1) Species with two nuclei, bodies circular in cross section. (2) Species with many nuclei, body circular or broadly oval in cross section. (3) Species with many nuclei, body flattened. To these we may now add (4) Species with two nuclei, body flattened. The nuclei measure 20m across, and are circular in outline, and placed obliquely behind each other. The chromatin material is scattered about in masses and is not arranged in any definite order. There is no differentiation into ectosarc and endosarc visible from a general surface view, and the protoplasm appears vacuolated. During movement the posterior portion of the body shows a ridged or rucked appearance as indicated in figure 81, b, so that it seems to be contracted towards this end, and in this way it moves Fig. 81.—Zelleriella binucleata. (After Rafb*.) Thei heavy lines in 6 (shaded IN Raff's drawing) represent "ribs"; o is an edge view. Measurements of an ordinary individual,—Length of body, mm.; width of body. mm.; diameter of nucleus, mm. This species resembles in body form Z. paludicolae from Paludi- cola hTachyops and P. Mhronii, but has a more definite, though slight, posterior point. Its nuclei are doubtless seldom in mitosis or Raff would have described their appearance during this phase. The resting nuclei are considerably larger than in Z. paludicolae. It is in all likelihood a distinct species, though study of the mitosis would be desirable before definitel}' determining this point. Z. hi- nucleata closely resembles in body from the shorter and broader daughter cells of Z. hrasiliensis from Leptodactylus ocellatus., but in the latter species the n
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