270 ' WALKER. 



In non-dysenteric stools that have become formed encysted entamoebae 

 make their appearance. These cysts (fig. 11) are developed, as in the 

 case of the order Coccidiida, only in the intestinal tract of the host, 'and 

 not in the evacuated fseces. If the process of encystment has already 

 begun before the entamcebce are passed in the stool the development of 

 the cysts may continue outside of the host ; but motile and resting enta- 

 moebse quickly degenerate and disintegrate in cold stools. The mature 

 cysts usually contain 8 nuclei of the same structure, but smaller and poorer 

 in chromatin than the -nuclei of the trophozoite; cysts containing more 

 than 8 nuclei are occasionally seen. AVliether such cysts represent a dif- 

 ferent species or variations in the same species, it is difficult to say. In 

 the development of these cysts Schaudinn described a complicated series 

 of nuclear changes, including an autogamous copulation of reduced nuclei, 

 that preceded the formation of the 8 nuclei in the mature cyst. Such a 

 reproductive process would constitute a sporogony comparable with that 

 taking place in the order Coccidiida. The mature cyst would correspond 

 with the sporocyst and the nuclei to the nuclei of the 8 sporozoites that 

 are supposed to be developed when the cyst reaches the intestine of a new 

 host. However, I have been unable to observe any stages in the develop- 

 ment of the 8 nuclei in the cysts which could be interpreted otherwise than 

 straight-forward nuclear division. Dobell (1909) has come to the same 

 conclusion from his study of the development of the multinuclear cysts of 

 Entamoeba ranarum,. If this interpretation of the process be correct then 

 it must be considered either as a schizogony in which the cyst would be 

 a schizocyst and the 8 nuclei the nuclei of the merozoites that are devel- 

 oped in the intestine of the new host; or possibly as a gametogony, com- 

 parable to that occurring in the order Gregarinida, in which the 8 nuclei 

 would constitute the nuclei of gametes that are formed and which 

 copulate in the intestine of the new host. 



Entamoebae of the coli and nipponica varieties have been observed only 

 in the stools of healthy persons or of persons suffering from diseases 

 other than dysentery; but it is possible that they might occasionally be 

 found associated with another type of entamoeba, about to be described, 

 in dysenteric stools. In such cases they would represent double infec- 

 tions. Of the two varieties the coli is found much the more frequently. 

 The nipponica variety may be encountered alone, alternating with the 

 coli variety in different stools of the same patient, or associated with the 

 coli variety in the same stool. Transitional forms between the two 

 varieties are frequently seen, and the 8-nuclear cysts have been found 

 associated with both the coli and the nipponica varieties of entamoeba. 



The entamoebse found in the stools of cases of amoebic dysentery, in 

 the pus of amoebic liver-abscesses, and in sections of dysenteric intestines 

 and of amoebic liber- abscesses, present certain morphological differences 

 from the entamoebae found in non-dysenteric stools which appear to be 



