ALL CHARACTERS ARE EQUALLY ACQUIRED 15 



growth of the blacksmith's arm which results from the nature of 

 his employment, or the thickening of the skin in the palm of the 

 hand which results from rough labour. 



29. Second, since nothing can be used or injured before it 

 exists, characters that develop under the stimulus of nutriment are 

 always the first to reappear. They are the earliest products both 

 of racial evolution and individual development. Therefore all 

 characters that arise through use or injury are * modifications ' of 

 those that arose under the stimulus of nutriment. But this creates 

 no real distinction, for all growth, whether in the embryo, foetus, 

 infant, child, or adult, whether arising in response to nutriment, 

 injury, or use, is a modification, due to cell-multiplication, of 

 previous growth. Nevertheless, since changes due to the stimulus 

 of nutriment arise gradually and insensibly, whereas those due to 

 injury are usually impressed in a very obvious way on pre-existing 

 characters, and those recognized as due to use are also so impressed, 

 the first have seldom been recognized as ' modifications,' while the 

 second and third have been so recognized. At any rate, the names 

 ' modification J and ' acquirement ' have been especially applied to 

 the effects of injury and use. That is, it has been implied that these 

 stimuli alter the individual in such a way as to make him different 

 from what, if I may use the expression, nature intended him to be. 

 Obviously, however, the reasoning here is superficial and inexact. 

 The error arises because the thinking is in terms, not of the germ- 

 plasm which carries the hereditary potentialities of individual, but 

 of the individual himself, who only develops such of his traits as he 

 happens to be stimulated to develop. As I say all characters are 

 equally rooted in the germ-plasm, all are equally products of 

 evolution, and all arise equally in response to stimuli. They are 

 all ready to arise, and they all arise inevitably if the right stimuli 

 be forthcoming. Whether they do, or do not arise, depends, not 

 on the nature of the individual, but on that of the environment. 

 It is as ' natural ' for him to develop a scar or a callosity 

 under the right conditions as to develop a beard or a hand. In 

 any case he fulfils his nature. 



30. Half a century of controversy has resulted from an 

 insufficient appreciation of the fact that the characters which 

 develop under the stimulus of injury and use are as closely related 

 to the germ-plasm, are as natural to the individual, as those which 

 develop under the stimulus of nutriment. Biologists are accustomed 

 to divide all the characters of living beings into those which are 

 ' inborn ' and those which are * acquired,' and while all biologists 



