168 EVOLUTION AND GENETICS 



lens serum ; of Griffith and Detlef sen on the effects 

 of long continued rotation; of Bagg and Hanson 

 and Little on some of the effects of radium and of 

 X-rays. To give a fair treatment of the interesting 

 results that have come out of this work would re- 

 quire a detailed account of the special conditions 

 involved in each case. To make a generalized state- 

 'ment that would cover them all would undoubtedly 

 mislead the reader. I shall attempt, therefore, a com- 

 promise between these extremes. 



JNIany of the facts can be accounted for on the 

 view that the reproductive cells have been directly 

 injured by the treatment, and since there is evidence 

 that the chromosome mechanism is the basis for the 

 transmission of the hereditary elements, one may 

 even go further and suggest that the chromosomes 

 have been altered. Xow, embryologists have been 

 familiar for a good many years with the injurious 

 effect of alcohol, of X-rays, and of radium on the 

 chromosomes in causing irregularities in their dis- 

 tribution, and with the consequent injurious effects 

 on the developing embryo, so that one need not go 

 far afield to find evidence in support of the view that 

 injuries produced on the germ-cell may affect the 

 individual that comes from it. How far the injuries 

 induced by these agents are sj)ecific, and how far 

 general is difficult to state at present ; but since, as 

 Stockard has pointed out, the organs affected are 



