178 University of California Publications in Zoolngij [Vol. 20 



continue from the binucleate stage until even after eight nuclei are 

 formed and budding begins. 



The "glycogen" vacuole (pi. 20, figs. 11-13) is centrally located, 

 and is relatively very large, in extreme instances filling seven-eighths of 

 the diameter of the cyst (pi. 20, fig. 11). At first it is spheroidal, but 

 is indented on one side by the enlarging nucleus. In the binucleate 

 stage the nuclei at first lie close together, but later are found on op- 

 posite sides of the vacuole, which they deeply indent. In later stages 

 the cytoplasm comes more and more to encroach upon the contents of 

 the vacuole, appearing in optical section as ridges or tapering pro- 

 cesses (pi. 20, fig. 14). 



The structure of the contents of this vacuole in the fresh cysts and 

 in those in the iodine-eosin stain is that of a homogeneous, undiffer- 

 entiated substance, though in a few instances a faint reticular mesh 

 could be detected within it. In preparations passed through aqueous 

 solutions in staining the contents of the vacuole are entirely removed. 

 Its substance does not stain brown readily, if at all in some stools, in 

 iodine-eosin. It remains in such stools wholly unchanged for hours 

 in this stain. In smears in Best 's carmine and in celloidin sections in 

 the same stain it remains unstained or at the most slightly tinged with 

 pink. In a few stools only were we able to find cysts giving anj^thing 

 resembling a characteristic glycogen reaction in iodine. In one in- 

 stance they were in a stool passed after three weeks of treatment with 

 antimony trioxide and in another in stools after phenolax had been 

 given. The stool contained a number of moribund and pathological 

 amoebae, and we found a few advanced cysts in which the central 

 vacuole stained a deep reddish brown and was somewhat broken up. 

 This failure to react normally and readily to iodine leaves the nature 

 of the substance in this vacuole somewhat problematical. It may be 

 that the heavy cyst wall interferes with the typical glycogen reaction 

 of the contents as it does with fixation and staining. The occurrence, 

 period of existence in the life cycle, morphological relations, solubility 

 in water, and stainability (in a few instances only), all indicate that 

 it is glycogen, or some substance very similar to it. 



The chromatoidal bodies (pi. 20, figs. 11-16; pi. 21, figs. 17, 19) 

 are quite similar to those of Endamoeia coli, but somewhat stouter 

 and less acicular. They first appear in the uninucleate, and especially 

 in the binucleate cysts in the thin film of protoplasm surrounding the 

 glycogen vacuole as numerous small flecks, blades, granules, or pointed 

 fusiform bodies staining deeply in iron haematoxylin in the typical 



