VIII. THE INHERITANCE OF ACQUIRED CHARACTERS 401 



rition, if they are milked regulary, and lactation may be induced in 

 virgins, or women many years past the menopause, by repeated stimu- 

 lation of the nipples through sucking. In this connection, many workers 

 believe that nervous impulses from the nipple affect pituitary func- 

 tion. Further, it is stated that the acquisition of new modes of 

 behaviour as a result of experience cannot occur in the absence of 

 hormonal influences (76). 



Thus the pattern developed by use in the local somatic cells can 

 be ti'ansmitted to the germ cells by the "virus" whose function may 

 be strengthened by the cooperation of hormones. If the pattern trans- 

 ferred thus to a certain gene in the germ cell is strong enough to be 

 preserved, even if partially, until the individual developed from the 

 germ cell begins to use the organ in question, the pattern will be 

 accumulated in successive generations resulting in a striking develop- 

 ment of the organ. However, since such a development may be also 

 reversible, disuse will lead to the disappearance of the character, 

 although the disappearance will become more and m.ore difficult if the- 

 use extends over generations. 



