OF ENVIRONMENT 127 



ifications in some characters stand apart from the condi- 

 tion of the parents without intergrades, at other times 

 the same modifications have intergrades; some charac- 

 ters, as far as known, never have intergrades and some 

 always show them, and there is no place where one can 

 draw a line and say that on one side all are discontinu- 

 ous variations and on the other side they are continuous. 

 Fourth: The modifications produced never, as far as 

 known, segregate the characters in subsequent genera- 

 tions, indicating a condition different from hybrids. In 

 this respect my results are like those of MacDougal 

 with plants." 



Obviously the subjection of an entire organism 

 to the influence of an enveloping factor implies 

 also its action upon the soma as well as upon the 

 germ, and vi^hile necessarily the possibility of 

 some secondary or parallel inductions are not 

 entirely ehminated, yet an examination of the 

 detail of the experiments points unerringly to 

 the conclusion that the major effect is due to the 

 action of the external agency on the egg or sperm. 

 The soma is indeed the most immediate environ- 

 ment and medium of the germ-plasm, and its 

 activities must interlock most intricately vdth 

 those of the egg and sperm, in what manner has 

 already been suggested. 



EFFECT OF RADIATIONS ON GERM-PLASM 



Somewhat easier of analysis are the effects 

 produced by such forms of energy as radiation 

 of known character and measured wave-length 

 as illustrated by the results secured by the use of 

 X-rays, Roentgen rays, and radium emanations. 



