128 THE DIRECT INFLUENCE 



In general it may be said that such forms of 

 energy retard growth and compel an incomplete 

 differentiation of tissues when applied to an indi- 

 vidual before maturity, producing serious delete- 

 rious effects if applied afterward. When eggs 

 or sperm are treated by these agents, the most 

 profound disturbances may ensue in the primary 

 divisions, and the ontogeny of individuals aris- 

 ing from a fertilization, either component in 

 which has been subject to such action, shows a 

 destruction of correlations and great disturbances 

 in symmetry, according to the most recent tests 

 of MacGregor with frogs. In most of these 

 cases the disturbances were so great that the indi- 

 viduals concerned were incapable of reproduc- 

 tion, and nothing further concerning their effect 

 on heredity was possible. The fact that the re- 

 sults were of the same general character, whether 

 the egg or sperm was subjected to the action of 

 the experimental agency, whether held in the re- 

 productive tracts of the animal or wholly free, is 

 a matter of some importance, since it eliminated 

 the intervention of the soma as a possible source 

 of modification of the results. 



Recently Dr. C. S. Gager has completed an 

 extensive study of the influence of radium on 

 plants so applied that the elements subjected to 

 its action survived and were capable of reproduc- 

 tion. An examination of the effects on the nu- 

 cleus as well as the structure of the soma was 

 made with some highly interesting results. 



