ELEMENTARY MORPHOGENESIS 



29 



very much twisted thread. This thread breaks, as it were 



FIG. 1. DIAGRAM OF CELL-DIVISION (after Boveri). 



a. Resting cell ; the chromatin distributed in the form of small granules inside the 

 nucleus. Outside the nucleus is the "centrosome," not mentioned in the text. 



6. Beginning of division ; the chromatin arranged in the form of a long thread. Centro- 

 some divided in two. 



c. The thread of chromatin cut into four parts, the " chromosomes." 



d. The four parts of the chromatin arranged symmetrically between the centrosomes and 



the star-like "spheres." 



e. Each of the chromosomes split at full length. 



/. Beginning of division of protoplasm ; the two parts of each chromosome separated. 

 g. End of cell-division. 



by sections, into almost equal parts, typical in number for 

 each species, and each of these parts is split at full length. 



