250 BIOLOGY AND ITS MAKERS 
show in resting-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. 
Fic. 79.—Diagram of the Chief Steps in Cell-division. 
(After Parker as altered from Fleming.) 
division exhibit the rod-like chromosomes, as shown at 4, 
b, and c. 
Centrosome.—The discovery (1876) of a minute spot of 
deeply staining protoplasm, usually just outside the nuclear 
