MITOSIS AND AMITOSIS. 413 



cells and embryonic cells it would deal a fatal blow to that 

 theory. The occurrence of amitosis in fully differentiated tissue 

 cells or in cells which do not undergo division would not affect 

 the chromosome theory. 



2. When direct division of the nucleus occurs it is rarely if 

 ever accompanied by division of the cell body. The individual 

 nuclear vesicles or karyomeres are not whole nuclei but frag- 

 ments of a nucleus and when the cell actually divides these 

 karyomeres combined form the typical number of chromosomes 

 which unite into a single spindle and divide in the typical manner, 

 as recently shown by Macklin. 



3. Many apparent cases of amitosis are merely modified 

 mitoses of which the following forms are described in this paper: 



(a) The scattering of chromosomes and their failure to unite 

 into a single nuclear vesicle. 



(6) Mitotic division of the nucleus without division of the 

 cell body and the consequent formation of binucleate or poly- 

 nucleate cell. 



(c) The failure of daughter chromosomes to pull apart in the 

 spindle and the consequent formation of chromatic connections 

 between daughter nuclei. 



(d) The persistence of the nuclear membrane with division 

 of the chromosomes by mitosis and of the nuclear vesicle by 

 constriction. 



4. There is not a single wholly conclusive case in which amitosis 

 has been shown to occur in the division of normally differentiating 

 cells. Therefore the attempts to disprove the chromosome 

 theory in this way have failed. 



5. Mitosis and amitosis are fundamentally unlike. Mitosis 

 is the one and only method of bringing about equal division and 

 distribution of the chromatic material of the nucleus. Amitosis 

 is not a genuine divisional phenomenon at all but merely a 

 means of increasing the nuclear surface and of distributing 

 nuclear material throughout the cell, comparable to nuclear 

 lobulation, fragmentation or distribution. These two processes 

 are not equivalent or even comparable nor may one of them be 

 converted into the other. 



