THE PHYSICAL BASIS OF LIFE 



18 



on tlio meelianism of Mendelian heredity. Tliese experi- 

 ments, (liio especially to Morgan, Stiirtevant, Bridges and 

 a large group of their co-workers, have accumulated and 

 thoi'oiighly analyzed a great body of accurate data in a 

 series of works that have almost revolutionized the study 

 of heredity.^ 



FIG. 5 

 Diagram of the closing phases of cell-division, showing final stages of the two 

 types shown in Fig. 3. 



I regret the necessity that limits my account of these re- 

 searches, and of what led up to them, to a bare indication 

 of their most general results. They have, in the first place, 

 finally demonstrated the fact, indicated in a more jreneral 

 way by earlier observers, that the nuclear threads or 

 chromosomes stand among the primary factors of hered- 



