130 University of Calif orni-a Publications in Zoology [Vol. 20 



or to about 0.25/^. This localized- thickening, together with the pro- 

 jection, forms convenient diagnostic characters for the identification 

 of these cysts, and for their distinction from ovoidal and ellipsoidal 

 cysts of Endolimax buetschlii or from the occasional ellipsoidal or 

 subspheroidal one of Endamioeba dysenteriae. 



The body of the flagellate may not completely fill the cyst, retract- 

 ing away from the anterior projection in stained cysts. Elsewhere it 

 lies in intimate contact with the wall of the cyst. 



The orientation of the cyst is determined by the position of the 

 flagellate within it. Normally or usually the anterior end of the 

 flagellate, which is distinguished by the location of the compound 

 blepharoplast, appears to be directed towards the tapering end of the 

 cyst (pi. 16, figs. 7, 10). There are, however, cysts in which this 

 relation of cyst and flagellate is reversed (pi. 16, figs. 9, 11). This 

 condition appears to be brought about bj^ the turning of the flagellate 

 within the cyst after the wall is completed and the form and orienta- 

 tion of the cyst determined. The rounded subspheroidal cysts (pi. 16, 

 fig. 8) may be caused by the rotations of the flagellate within the cyst 

 during its more plastic condition. 



The organs of the free-moving flagellate, with the exception of 

 the free flagella, are all visible in the stained cysts. In stained cysts 

 with diifuse glycogen (pi. 16, fig. 10) the cj'toplasm was rather 

 uniformly and finely alveolar. In a few cases the glycogen was 

 clumped in clouds, rather diffusely margined, scattered in the cj'to- 

 plasm (pi. 16, fig. 8). In stained cysts these glycogen masses are 

 dissolved out, leaving coarser vacuoles (pi. 16, fig. 9). Very rarely 

 was the glycogen condensed in one or more dense, deeply staining, 

 iodophylic masses which became dark brown in iodine-eosin and dis- 

 solved out, leaving large vacuoles (pi. 16, fig. 7), when treated with 

 aqneoiis solution, as in the iron haematoxjiin staining method. Dobell 

 and Jepps (1917) have figured two such glj'cogen-laden cysts. 



The amount of glycogen within the cj'st decreases with age, as it 

 does in the glycogen-bearing cysts of the three species of human 

 intestinal amoebae. There is great variation in the cysts in different 

 stools in the amount of glycogen contained therein, but less variation 

 among the cysts of a given stool. Older binucleate cysts lack the 

 glycogen vacuoles. 



The other cytoplasmic contents of the cyst are the chromatoidal 

 bodies. These may or may not be present and when found vary greatly 

 in number and location. They are ellipsoidal, ovoidal, or spheroidal 



