Chromonemata 



13 



16 chromosomes, or the same number as the parental cell. As 

 the result of this mechanism, each cell of the body has the same 

 number of chromosomes. These body cells, as distinguished from 

 the reproductive cells, are called somatic cells, and ordinary 

 mitosis of body cells is frequently called somatic mitosis to dis- 

 tinguish it from the type of mitosis which forms reproductive 

 cells and which will be described in a later chapter. 



Mitosis in Animals 



Mitosis in the onion root tip is frequently studied in both 

 botanical and zoological courses. It is typical of higher plants 

 and is fundamentally the same as in the higher animals, although 



d e 



Fig. 4, Mitosis in an animal cell: (a) prophase; (6) metaphase; (c) 

 early anaphase; (d) late anaphase; (e) late telophase. Diagrammatic. 



there are some differences in animal cells that should be con- 

 sidered. The chief difference between the two groups of or- 

 ganisms lies in the formation of the spindle, which arises in 

 animal cells from two centrosomes (Fig. 4). 



Chromonemata 



Only an indication so far has been given of the internal struc- 

 ture of the chromosome. When stained with hematoxylin. 



