THEORIES IN PRACTICE 367 



modifications as these may be inherited. And if 

 the opponents of the theory of the transmission 

 of acquired traits can get any comfort out of the 

 claim that such modifications directly affect the 

 germ plasm, we need not wish to rob them of 

 that cold comfort. 



Details as to the special manner of inheritance 

 aside, we may accept it, I think, as the only logi- 

 cal conclusion from a wide survey of the facts of 

 heredity and evolution, that all modified charac- 

 ters that affect the constitution of the individual 

 are heritable. Even the slightest modification 

 of structure due to altered nutrition, to changed 

 temperature, or the like, probably makes its in- 

 fluence felt on the next generation in exact pro- 

 portion to its value in the great complex scheme 

 of characters with which it is associated. 



But this statement must not be misinter- 

 preted. It must not be supposed that any minor 

 modification of an individual can influence, ex- 

 cept in an infinitesimal way, the inheritance of 

 the offspring of that individual. 



For the new modification will be, in the nature 

 of the case, only as an alien drop or two in an 

 ocean of hereditary tendencies. 



Or, stated in somewhat more modern terms, 

 the hereditary factor that represents the new 

 modification will be as one minor factor among 



