DEFINITION OF THE PROBIEM 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 



