1922] Sivezij: miosis in Endamoeha Coli 317 



At the beginning- of encystment tlie cytoplasm generally contains 

 a large amount of glycogen. This may be so great in extent as to 

 give a dense brownish color to the entire cyst in iodine-eosin stain, 

 or it may be localized in small spheres with outlines more or less 

 sharply defined. With the process of fixation the glycogen forms a 

 single mass or several large masses whose locations, in stained prep- 

 arations, appear as large, clearly defined vacuoles (pi. 29, figs. 3-7), 

 the glycogen itself having been dissolved in the aqueous solutions in 

 the process of staining. 



M1T0SI8 



Binary fission of Endamoeha coli in its active form has not thus 

 far been described hy any investigator. It is probable that it occurs 

 mainly in the upper part of the colon and occupies such a short time 

 that individuals undergoing this process do not reach the exterior 

 before its completion. Binueleate free individuals may sometimes be 

 present (Dobell, 1919), but no clue to their further history has been 

 found. 



In the following paragraphs, an outline of the process of mitosis in 

 the encysted form of Endomocha coli will be given. Some minor gaps 

 in this process have yet to be filled, but a sufficient number of stages 

 are here presented to indicate the line of development throughout. 



PROPHASE 



The prophase of mitosis is marked by a considerable increase in 

 the amount of chromatin contained within the nucleus. This is rela- 

 tively small in the normal trophozoite and is distributed in tj'pical 

 fashion, with chromatin granules attached to the nuclear membrane, 

 and a small, spheroidal exeentric karjosome (pi. 29, fig. 2). A few 

 chromatin granules may also be found on the linin reticulum which 

 fills the nucleus. At the approach of the prophase the linin network 

 disappears and the karyosome becomes lost in the mass of chromatin 

 found in the center of the nucleas (pi. 29, fig. 1), usually distributed 

 in irregular masses and granules. At the same time tlie luicleus 

 becomes elongated and the larger masses of chromatin become dis- 

 tributed as numerous small granules filling more or less of the interior 

 (fig. 3). This is the stage most abundant in amoebae containing two 

 nuclei. In fact, most individuals of the two- and four-cell stages in 

 Eudaiimcba coli in our nuiterial seem to be in the early prophase. 



