iv HOMOCHRONOUS INHERITANCE 167 



which certainly often depend upon acquirement, and which 

 must contribute to the modification of the organic world, 

 namely, the facts of the inheritance of characters of the 

 parents by the children in such manner that they appear in 

 the latter at the same age in which they occur in the former. 

 This kind of inheritance has been called homochronous ; it is 

 obviously a necessary consequence of the law of correlation. 

 Thus the characters which accompany sexual maturity can 

 only appear when the sexual organs have reached maturity. 

 But many characters belong here which have been acquired 

 by use and habit, as the fact, to be discussed subsequently, 

 and already mentioned by Darwin, that the peculiarities of 

 handwriting when inherited by a son from his father only 

 appear at a ripe age. 



On account of the contrast in which it stands with this 

 homochronous inheritance, I must here mention an ob- 

 servation which at the same time illustrates the influence 

 of the condition of the organism as a whole, at the time of 

 generation, upon the germ. 



I observed that children of very old parents, especially of 

 old fathers (male preponderance) have in their early years 

 as children features of a remarkably old appearance. 



I have repeatedly tested the correctness of this observation 

 by appeal to impartial witnesses, and am able to state it with 

 certainty. 



A senile expression of face may certainly be called a 

 character acquired through use. 



In the following I will adduce a few additional instances 

 of the inheritance of characters acquired by exercise, some 

 due to habits of life, some to training, and some instances of 

 mental characters, although I shall subsequently have to de- 

 vote special consideration to the latter, above all, to instinct. 



Is it not due essentially to better nourishment, to 



