THE BEGINNING OF DEVELOPMENT 



29 



Fig. 2. Fig. 3. 



Fig. 2, — Diagram of ordinary cell-division, (a) The chromo- 

 somes appear, already double, in the nucleus, (b) The cell 

 divides and one-half of each double chromosome goes to 

 each daughter cell 



Fig. 3. — Diagram of cell-division during the formation of 

 the germ-cells, {a) The chromosomes apjjear single in the 

 nucleus, (a') The two chromosomes of each kind lie side 

 by side, {b) The cell divides and one chromosome from each 

 pair goes into each daughter cell 



