THE INTESTINAL PROTOZOA OF FROGS AND TOADS. 275 
Fig. 55.—Individual with nucleus in process of dividing. (Leitz ~; in. 
oil-imm. xX oe. 5.) 
Fig. 56—Ameba with two nuclei—presumably in a stage just before 
fission of cytoplasm. (Heidenhain Fe-hematox. Leitz j1, in. x oc. 5.) 
Fig. 57.—Individual with distorted nucleus. The distortion is 
brought about by the nucleus being forced into a pseudopodium. The 
condition suggests—falsely—an amitotic division. (Delafield and eosin. 
Leitz 3, in. x oc. 5.) 
Fig. 58.—Large, actively feeding ameba, with modified nucleus. 
(Hypertrophied ; drawn on smaller scale than other figures. Heiden- 
hain and eosin, Zeiss 2 mm. apo. oil-imm., comp. oc. 6.) 
Fig. 59.—Nucleus of same individual more highly magnified (comp. 
oc. 12.) 
Fig. 60.—Amcba about to encyst. Note formation of karyosome 
and protrusion of chromatin into the cytoplasm (on left of nucleus). 
Fig. 61.—Encysting ameeba. The karyosome is now very well formed, 
the chromatin masses are very conspicuous in the cytoplasm, and the 
vacuole has made its appearance. No cyst membrane is as yet to be 
seen. 
Fig. 62.—An ameeba, at a similar stage, which has been invaded and 
killed by bacteria. These have filled the cytoplasm and attacked the 
nucleus, thus giving rise to an appearance which suggests a resolution 
of the nucleus into chromidia. (Heidenhain.) 
Fig. 63.—A. uninucleate cyst, living animal. Nucleus, chromatin 
masses, and vacuole wellseen. (Leitz 2 mm. oil-imm. apo., comp. oc. 12.) 
Fig. 64.—A similar cyst, stained. 
Fig. 65.—Nucleus beginning to divide. 
Figs. 66, 67.—Two succeeding stages of the spindle figure of the first 
nuclear division. (Fig. 67, Heidenhain and eosin.) 
Fig. 68.—Later stage, in which the spindle is being constricted ,into 
two. 
Fig. 69.—Still later. The two daughter-nuclei are now clearly 
differentiated, but not yet separated, owing to a part of the spindle 
persisting between them. (Heidenhain and eosin.) 
Fig. 70.—Cyst containing two nuclei, formed by the division of the 
original nucleus. (Heidenhain and eosin.) 
Fig. 71.—The two nuclei beginning to form the spindles of the second 
nuclear division. Note the way in which the spindle is being formed 
by extension of only one pole—not by prolongation between two 
opposite poles (cf. fig. 65). (Heidenhain and eosin.) 
