48 



BUILDING MATERIAL OF LIVING THINGS 



This type of cell division is called mitosis, and may be divided into four stages : 

 the prophase, shown by 1, 2, 3, 4, 5 ; the metaphase (6) ; the anaphase (7, 8) ; and the 

 telephase (9) . A material in the nucleus (n) called chromatin (ch) generally separates 

 out into a thread (2), a band (3), and then breaks into parts, called chromosomes 

 (4, cs). These arrange themselves at the center of the cell (5). Then the chromo- 

 somes split lengthwise (6) and pass one half to each end of the cell as shown in 7 

 and 8. A new nuclear membrane (n m) , and a new nucleolus {ns) — are formed 

 in 9. Compare 9, the telephase, with 1, the prophase. Two little dots (1, c) in 

 the cytoplasm are called centrosomes. These separate from each other but are 

 connected by tiny threads, known as spindle fibers (3. st). Look for the centro- 

 somes and spindle fibers in all the diagrams. 



