1923] Kofoid-Swezy-Kessel: On the Genus Councilmania 443 



exception rather than the rule. Small masses with irreg:iilar ends 

 (fig. 19) or chips or spheres of chromatoidal substance (fig. 15, 16) 

 are commonly encountered. 



Tlie budding cyst of C. decumani is characterized by the absence 

 of chromatoidal material and by few chromophile ridges, only one 

 small ridge having been found in this species to date. Buds, however, 

 are common and are produced by the same method of reproduction 

 in this species as in the others belonging to this genus. 



The normal cysts range from 12 to 20 microns in diameter but 

 one large 16-nucleate cyst has been found, measuring 22 microns. 

 The average diameter of the cysts of this species is 15.5 microns. This 

 species occurs in both mice and rats of our culture colony. 



KEY TO SPECIES OF COUNCILMANIA 



Cysts spheroidal to ellipsoidal, 8-34, generally 16-20 microns in longest diameter; 

 in 8-nucleate cysts the nuclear membrane is generally very faint with little 

 peripheral chromatin; diameter of nuclei 3.5 microns; karyosome central, com- 

 posed of numerous coarse, irregular granules; 8 chromosomes laflcuri 



Cysts generally spherical, 15.8 (13-19) microns in diameter; very little peripheral 

 chromatin at any stage in the nuclei of the cysts; nuclear membrane very 

 faint; diameter 3.4 (2.75-3.75) microns; karyosome central composed of 5-7 

 dispersed fine, uniform granules; 6 chromosomes muris 



Cysts spherical, 15.5 (12-22) microns in diameter; peripheral chromatin in several 

 rather large, distinct blobs; nuclear membrane distinct, diameter 2.8 (2.5-3.0) 

 microns; karyosome exccntrie, composed of massed granules, 4 chromosomes.... 



decumani 



Fig. 17. Pour-nucleate cyst, two nuclei in prophase, showing karyosome break- 

 ing up and peripheral chromatin blobs. The other two nuclei are in early anaphase 

 showing the spindle, the four chromosomes having just divided. The eentrosomes 

 are connected by an intradesmose. 



Fig. IS. Eight-nucleate cyst showing clustered chromatoidal bodies. The 

 nuclei are characteristic resting nuclei of this species with excentric karyosome 

 more massed than in C. muris but with a tendency to dispersion and with char- 

 acteristic chromatin blobs on nuclear membrane. 



Fig. 19. Eight-nucleate cyst with no chromatoidal bodies and with bud in 

 early formation. Note absence of chromophile ridge. The nuclei show the typical 

 structure common to this species. 



