1924] Kcxsel: Amorhac of CuJture Rats and Mice 509 



Mitosis 



Accurate cj-tological interpretation of cell phenomena in parasitic 

 amoebae is difficult at best and requires the careful and detailed study 

 of a great number of specimens. In the present investigation, 170 

 drawings have been made with the aid of the camera-lucida and 

 large numbers of other forms have been studied in detail with the 

 best magnification available. The 62 figures on the plates have been 

 chosen as the most representative of the various phases of cytological 

 development. 



The developmental process in this species of amoeba is similar in 

 method to that recorded for other para.sitic amoebae, and except in 

 specific differences the mitotic stages simulate those already described 

 for C. Uifleuri (Kofoid and Swezy, 1921) and for Endamoeha coli 

 (Swezy, 1922). The nucleus in the mononucleate cyst divides mito- 

 tically to form two nuclei, a second division then occurs to form four 

 nuclei, and finally a third division, which results in a typical eight- 

 nucleate cyst which is regarded as the mature cyst of this species. 



The typical resting stage of the nucleus has already been described. 

 This persists for a longer or a shorter time between each division, is 

 always typical, and is found most commonly in the eight-nucleate 

 cysts. The second division seems to require a longer time than either 

 of the following divisions, judging from the fact that mitotic figures 

 are most commonly encountered in binucleate cysts. Owing to the 

 presence of the glycogen vacuoles, the nuclei are usually somewhat 

 flattened and pressed to one side of the cyst (pi. 44, fig. 11). 



Prophase. — The fact that more prophase stages were found than 

 stages of any other phase indicates that this period occupies a longer 

 time than any other phase of mitosis. During this stage there is a 

 complete reorganization and transformation of the contents of the 

 nucleus. The first indication of this phase is the arrangement of a 

 few small granules of chromatin on the nuclear membrane (pi. 43, 

 fig. 4). The granules of the karyosome become somewhat more dis- 

 persed than usual and numerous linin fibers connect the granules of 

 the karyosome with the chromatin granules on the nuclear membrane. 

 The granules on the membrane disappear and a darkly staining region 

 appears around the granules arranged in the middle of the cyst (pi. 43, 

 fig. 7 ; pi. 44, fig. 11 ) . About this time a distinct line, the intradesmose 

 (Kofoid and Swezy, 1921) appears between two of these granules 

 (pi. 43, fig. 6). These granules then pull further and further apart 



