Chemistry of Living Matter and Cell Division 



97 



celled plants, the division and increase may take place every few minutes 

 so that in the course of a few hours there are millions upon millions of 

 cells where before there was only one. 



Writers on Biology commonly hold that there are two ways in 

 which cell division comes about, but recent investigations tend to show 

 that this may be erroneous and that all cell division is probably mitotic. 

 One method is said to be the shorter and simpler way, in which the cell, 



Fig. 29. Diagrams Representing the Essential Phenomena of Mitosis. 

 A, resting stage; B, early prophase; C, late prophase; D, mesophase ; E, metaphase ; F, end 

 view of E; G, anaphase; H, late anaphase; I, telophase; J, late telophase. 



LABELS. 



1, centrosome. 7, cytoplasm. 



2, attraction sphere 8, cell wall. 



(centrosphere). 9, vacuole. 



3, nuclear membrane. 10, astral ray. 



4, nucleolus. 11, spireme. 



5, nucleoplasm. 12, aster. 



6, linin network and 13, spindle. 



chromatin. 



(Redrawn from Jewell Models, by permission of General Biological Supply House, Chicago.) 



14, chromosome. 



15, central spindle fibers. 



16, mantle fibers. 



17, beginning of new cell wall. 



18, chromosomes breaking down. 



19, spindle remnants. 



20, new cell wall. 



without any previous changes that could be observed, splits in two parts. 

 But the longer method, known as mitosis (Fig. 29), is the more com- 

 mon, and is the one which must be studied in detail if any understanding- 

 whatever is to be obtained as to how plants and animals evolve from 

 the single original cell into the marvelous, complex organisms of adult 

 life. 



The cell, as described in the last chapter, has a network in the 

 nucleus that stains quite easily and readily. When this network is not 

 in the process of division the cell is said to be in the resting stage. In 

 the higher forms cell division takes place only after fertilization, that 



