1923] Kofoid^Swezij-Kessel: On the Genus Cowncilmania 441 



The nuclear structiire of the motile stages is, however, quite . 

 different in the individuals stained with iron haematoxylin where the 

 karyosome, instead of appearing as a number of dispersed granules, 

 occurs as a sphere or a crescent (fig. 15). The nuclear membrane is 

 slightly heavier than the nuclear membrane of C. muris and is com- 

 monly encrusted with discrete chromatin granules (fig. 15). 



This massing of chromatin material in blobs on the nuclear mem- 

 brane in the cysts is a characteristic of this species, such a condition 

 being common in some stages of nuclear division, and in the resting 

 stage, but not at the metaphase (fig. 17). The karyosome of this 

 species is more massed than the karyosome of C. muris or C. laflexiri, 

 but shows a tendency to dispersion throughout by minute irregu- . 

 larities on its margins. The karyosome is never so small nor so 

 characteristically massed as the karj'osome of Endamoeha, coH or 

 E. dysenteriae. 



The stages of mitosis are similar to those of other parasitic 

 amoebae (fig. 17). Four chromosomes, including one minute one, 

 are characteristic for this species. 



The typical resting nucleus is seen in figure 18. It is characterized 

 by a thin but distinct nuclear membrane upon which several heavy 

 chromatin blobs are encrusted. The number maj' vary from two to 

 six or eight, but usually four chromatin blobs are present. The 

 karyosome is excentric, larger than the karyosome of Endamoeha coli, 

 and shows a tendencj' to dispersion. 



The nuclei of Councilmania decnmani are on the whole smaller 

 than the nuclei of C. muris. Their average diameter in the binucleate 

 cysts is 4.6 microns and the range 4 to 5.2 microns ; while the average 

 diameter in the 4-nucIeate cysts is 3.8 microns, the range being from 

 3.1 to 4.4 microns, and the average diameter in the S-nucleate cysts 

 is 2.8 microns, the range being from 2.5 to 3 microns. 



This species of amoeba is poorer in chromatoidal material than 

 C. muris, the presence of masses of chromatoidal splinters being the 



Centrosomes are connected by an intradesmose. The nuclear membrane is thin 

 with no encrusted chromatin. 



Fig. 11. Four-nucleate cyst, one nucleus in metaphase and the other three in 

 prophase. Note dispersed condition of chromatin granules of nuclei in prophase, 

 The membranes are characteristically thin with no encrusted chromatin. 



Fig. 12. Eight-nucleate cyst showing typical chromophile ridge. The nuclei 

 show the characteristic, central, dispersed karyosome, and thin nuclear membrane 

 with no encrusted chromatin. 



Fig. 13. Budding cyst, showing tripartite chromophile ridge and exceptionally 

 large chromatoidal mass with splintered ends. The karyosomes are dispersed 

 granules and the nuclear membranes are faint. 



