DEFINITION OF THE PROBLEM 173 



conclusion. By all means let there be a critical discussion as 

 to the best definition of " an acquired character," " a modifica- 

 tion," " a somatic change induced on the body by environmental 

 or functional influences " ; by all means let there be a criticism 

 of terms and categories the minting of a perfectly unambiguous 

 word for somatic modifications would be most welcome : but if 

 the sheaves of facts and alleged facts are to be thrashed out 

 with the end of getting at the wheat of truth, we must adhere 

 to certain definitions notably, of course, to those given by 

 Weismann, who brought the problem in its modern aspect into 

 focus. Even a sense of humour should hinder a young medical 

 practitioner from thinking that he makes for progress by ad- 

 vancing an argument which has no cogency unless the biological 

 dictionary be first re-edited. It should be evident that a dis- 

 cussion over which some of the wisest heads in Europe and 

 America have pondered cannot be, as some have had the 

 effrontery to declare it, a mere play of words. Is it too much 

 to ask of those who are keen to break a lance with the Biologist 

 of Freiburg that they should first at least read The Germ- 

 Plasm ? 



What is an Acquired Character? In our previous dis- 

 cussion of " heredity and variation " we have briefly expounded 

 the distinction between germinal, blastogenic, constitutional, 

 endogenous " variations," and bodily, somatogenic, acquired, 

 exogenous " modifications." An acquired character, or a 

 somatic modification, may be defined as a structural change 

 in the body of a multicellular organism, involving a deviation 

 from the normal, directly induced during the individual lifetime 

 by a change in environment or in function (use and disuse), and 

 such that it transcends the limits of organic elasticity, and there- 

 fore persists after the factors inducing it have ceased to operate. 



Illustrations. Dwarfing of Japanese trees, deformation of trees 

 by the wind, blanching of plants grown in darkness, changes 

 directly induced by transplantation, persistent sun-burning, change 



