1915] Iafluejsce of Radium Eays 155 



to bear out llertwig's couclusioii that it is the chromatin of 

 the cell that is chiefly injured by treatment with radium, 

 and that when the injury is severe enough the damaged chro- 

 matin is eliminated and the egg develops parthenogenetic- 

 ally. 



There has been some criticism of Hertwig's explanation 

 of the action of radium on the ground that it does not go 

 far enough back into the organization of the cell, and it is 

 said that further explanation must ultimately be chemical 

 in nature. Packard, and Richards who recently published 

 an interesting artick' in Science on the biological effect of 

 radio-activity, have sought to explain its influence by the 

 efl'ect that radium has on certain intercellular enzymes; but 

 in the present state of oui' knowledge of biochemistry it 

 cannot be said that we know anything about chemical pro- 

 cesses that go on within the egg which can be regarded as the 

 causes of diflerentiation, though further information of this 

 nature is greatly to l)e desired. 



Chapei, Hii.]., X. C. 



