THE CELL AND THE CELL THEORY 



33 



plate is formed at the plane of division which later becomes 

 double, and then the two plates separate, or (c) two nuclear mem- 

 branes are built up inside of the old membrane, which then breaks 

 down, allowing the daughter nuclei to escape. 



" The cell body is the last to divide in amitosis, and in many, 

 perhaps the majority of cases, it does not do so at all" (21, p. 38). 



FIG. 7. Amitotic nuclear division in the follicle cells of a cricket's egg. (From 

 Dahlgren and Kepner.) 



The amitotic process is usually a sign of senescence or decadence in 

 a cell. Many cells divide by mitosis so long as there is actual 

 division of the cytoplasm as well as of the nucleus, but if the cell 

 body fails to divide, the nucleus alone may continue to multiply 

 amitotically, producing a multinucleate cell. " The commonly 

 received idea, at present, concerning amitosis is that it is a termi- 

 nal process in the cell's life activities, and is a method of securing 

 more nuclear surface for use in forced metabolism or secretion " 



(21, p. 39)- 



In concluding this account of cell division two points are worthy 

 of special emphasis. First, with regard to the continuity of the 

 chromatin, it may be said that the chromatin is continuous 

 from one cell generation to another. The cells resulting from 

 mitosis may differ greatly in size, but the chromatin seems to 

 be divided equally between them with great exactness. Second, 

 cells are never known to arise except from preexisting cells. These 

 two facts are perhaps the most important for us to keep in mind 

 as we go on to study the more complex problems of fertilization 

 and cell division in the many-celled animals, for growth in every 

 Metazoon is really nothing more than cell division and cell 

 growth. 



