SCHIZAMCEBA SALMONTS 
5 
ous fat globules. It also stains more deeply with iodine, indicating the formation 
of glycogen, which is evidently present in a diffused condition. 
Since the cysts may develop from mononucleate, binucleate, or multinucleate 
individuals, there is obviously great variation both as regards size and number of 
nuclei in the newly formed cysts. In fact, cysts are formed with as few as three 
nuclei, while others may contain a large number. However, the later history of 
the cysts is such as to make it impossible to determine with any degree of accuracy 
whether any particular cyst is newly formed or has already gone through a course 
of development in the encysted stage. Their further development is of particular 
interest, since no similar phenomena appear to have been observed in other species 
of amebse. These changes take place both in the stomach and intestine, and all 
stages may be found in both organs. In fact, no difference could be detected in 
cysts from the stomach and intestines and, unlike the vegetative stages, they are 
apparently indifferent to the surrounding fluids. 
While the newly formed cysts vary greatly in size, there is good reason to 
believe that the organisms continue to grow after encystment, since the percentage 
of large cysts with a correspondingly large number of nuclei is always much greater 
than that of the multinucleate vegetative forms. Furthermore, the division of the 
nuclei, followed eventually by division of the cysts themselves, also indicate growth 
during this stage. In striking contrast to the ameboid stage the cyst nuclei always 
divide by a primitive form of mitosis. The details of this process are shown in 
Figures 23 to 30. In preparation for division the karyosomes become enlarged and 
the chromatic material at one side develops a fibrous structure (figs. 23, 24, and 31). 
The chromatic granules, which in the resting nucleus are embedded in this material, 
become arranged in an irregular manner at the ends of the fibers nearest the nuclear 
membrane. A little later the group of fibers splits into two equal parts (figs. 25 
and 32), which separate and eventually come to lie on opposite sides of the karyo- 
some (figs. 27, 28, and 33). At this stage, which is evidently the metaphase, the 
mitotic figure extends across the nucleus with the karyosome in the middle of the 
spindle. The chromatic granules now form a deeply staining mass at the ends of 
the spindle fibers. Often they appear to be scattered along the sides of the spindle, 
but this may be due to the fact that the fibers are of unequal length. Shortly after 
this the karyosome becomes elongated and later constricted in the middle, as 
shown in Figures 29, 30, 33, and 34. Eventually the two parts separate, thus 
giving rise to two daughter nuclei similar in every respect to the original nucleus 
except in the matter of size. While this is evidently a form of promitosis no chro- 
mosomes could be detected in the karyosome, although it appears to have an 
indistinct fibrous structure when greatly elongated. The arrangement and behavior 
of the chromatic granules on the spindle fibers indicates that they should probably 
be considered as homologous with the blepharoplasts and centrioles of other protozoa. 
The details of this process of promitosis appear to be quite different from 
anything described in the literature. In some respects there is a superficial resem- 
blance to the nuclear division in the trophozoites of Amoeba tacbypodia (Glaser, 
1912; Ford, 1914) and of Nsegleria gruberi (Wilson, 1916). However, in both 
species the details of the process are quite different in several respects. The periph- 
eral chromatin, which collects at one side of the karyosome in these two species, 
44699—27 2 
