180 University of California Publications in Zoology [Vol. 20 



nuclei in the cysts. There may be no trace of peripheral chromatin 

 or only a layer of fine granules on its inner surface with an occasional 

 larger granule or two in this region, but not so heavy an incrustation 

 as in E. coli and E. dysenteriae. The intermediate zone is filled with 

 a substance which is often much less deeply stained than the surround- 

 ing cytoplasm, but in other eases may be slightly stained in iron haema- 

 toxylin as an indistinct reticulum. We find in the nuclei of cysts no 

 trace of inner clear halo and outer granular network in the inter- 

 mediate zone such as Dobell (1920) figures for E ndamocba coli in some 

 nuclei of the encysted stage. 



The lightly incrusted nuclear membrane and the wide, lightly 

 stained, intermediate zone make the nuclei of the cysts with eight 

 nuclei stand out in the darker cytoplasm with a distinctness not equaled 

 in other amoebic cysts of human stools. This is noticeable in prepar- 

 ations and is evident in some of the figures of Councilmania which 

 appear in the older literature among the figures of E ndamoeba coli, 

 such, for example, as those of Prowazek (1911, pi. 17, fig. 18). This 

 feature, the predominant asymmetry or lack of sphericity of the cysts, 

 and the peculiar karyosome make possible the critical distinction be- 

 tween the cysts of Councilmania and those oiE ndamoeba coli. 



There is no critical, cytological evidence from Councilmania which 

 lends the least support to the hypothesis of autogamy in amoebic cysts 

 proposed and defended by the Sehaudinn-Hartmann school of proto- 

 zoologists. 



DIMENSIONS 



The average size of the free amoebae when rounded up was 28 

 (20-35) microns in the ease of ten measurements of amoebae from one 

 stool. Smaller amoebae are sometimes seen which probably belong 

 to this species. The largest free amoeba we have seen in stained prep- 

 arations measured 35 by 63 microns. The amoebulae on escape from 

 the cyst have a diameter of 7 to 8 microns. The cysts range from 8 to 

 34 microns in diameter. In one fresh stool in which 150 of the more 

 spherical cysts were measured the range in longest diameter was from 

 11 to 34 microns, with the mode at 16 microns, the average at 16.5, and 

 114 cysts included between 16 and 20 microns. The curve of distri- 

 bution of these measurements showed a marked skew towards the 

 smaller diameters, and probably represents a small race of the species. 



