1923] Kofoul-Swezy-Kessel: On the Genus CouncUmanm 437 



dear spheres. The karyosome is large, central, and comijosi'd of 

 discrete granules, sometimes densely massed, sometimes dispersed 

 in a granular sphere or in a more or less complete ring. This dis- 

 persal takes on a variety of aspects and is modified by the approach 

 of mitosis when the karyosome migrates to the nuclear membrane and 

 divides. The two moieties migrate to the poles of the spindle and 

 spin out the meridional intradesmose between them. Except during 

 this period of migration and mitosis the karyosome tends to assume 

 a central location in the nucleus rather than an excentric one. The 

 excentricity, if present, is rarely marked. The nuclei of the 2-, 4-, 

 and 8-nucleate cysts have an average and range of 6 microns, 5-6 

 microns, 5.3 microns, 4-5.6 microns, 3.5 microns, 3-4 microns respec- 

 tively in diameter. The cysts are spheroidal, or ellipsoidal, often the 

 latter, with the longest diameter not over 1.1 the shortest one. The 

 cysts are generally 16 to 20 microns in longest diameter and range 

 from 8 to 39 microns. The cysts reach an 8-nucleate phase in the 

 bowel, and rarely go to a 16-nucleate condition before the budding 

 process begins. This is brought about by the opening of a minute 

 circular pore through the cyst membrane at or near the end of 

 the centrally located chromatoidal mass whose substance is dissolved 

 in the e.ytoplasm which escapes through the pore and causes it to 

 stain more deeply. The nuclei slip out with the cytoplasm and 

 amoebulae, each with a single nucleus, successively detach themselves 

 from the cyst. Mitosis may proceed within the cyst during the 

 process. 



Small amoebulae occur in stained smears adjacent to budding 

 cysts and empty cysts may sometimes be found in the stool. Chromo- 

 phile strands or ridges in the peripheral cytoplasm (figs. 6, 7) in a 

 single or a tripartite arc are formed prior to the opening of the pore 

 and appear to be associated with the chromatoidal body and the 

 subsequent location of the pore. The habitat is presumably the colon 

 and caecum. Cysts have been found by us in the contents of the 

 duodenal bucket by the Lyon method. In artificially infected culture 

 rats this species occurs in the caecum. 



Fip. 3. Four-nucleate cyst with disappearing glycogen vacuole, traces of 

 chromatoidal substance, four nuclei with dispersed granular, centrally or sub- 

 centrally located karyosomes, and considerable peripheral chromatin. 



Fig. 4. Eight-nucleate cyst with nuclei with less peripheral chromatin and 

 massed ring-shaped, central karyosomes, and centrally located chromatoidal body 

 with ragged ends. 



Fig. 5. Budding cyst with eight nuclei, chromatoidal substance contributing 

 to the outpouring cytoplasm, pore at the end of the chromatoidal body. Karyo- 

 somes ring-shaped and centrally located, nuclear membrane with little peripheral 

 chromatin. 



