BIOLOGY AND ITS MAKERS 



show in rcsting-stages of the nucleus; their substance is 

 present, but is not aggregated into the form of chromosomes. 

 Fig. 78 shows tissue cells, some of which are in the divid- 

 ing and others in the resting-stage. The nuclei in process of 



nu-rrl 



D 



E 





<Jir 





H 



'' \\ 



I (MM, V ' 

 i Rtialmm* \ 



I 



i 



' ' 



/ 



r .w 



FIG. 79. Diagram of the Chief Steps in Cell-division. 

 (After Parker as altered from Fleming.) 



division exhibit the rod-like chromosomes, as shown at a, 

 bj and c. 



Centrosome.--The discovery (1876) of a minute spot of 

 deeply staining protoplasm, usually just outside the nuclear 



