'HEREDITY. 443 



germ-plasma. Those who sustain the view that ac- 

 quired characters are inherited, must, I believe, un- 

 derstand it as thus stated. The character must be 

 potentially acquired by the germ-plasma as well as ac- 

 tually by the soma. Those who insist that acquired 

 characters are not inherited, forget that the character 

 acquired by the soma is identical with that acquired 

 by the germ-plasma, so that the character acquired by 

 the former is inherited, but not directly. It is acquired 

 contemporaneously by the germ-plasma, and inherited 

 from it. There is then truth in the two apparently op- 

 posed positions, and they appear to me to be harmon- 

 ized by the doctrine above laid down, which I have 

 called the Theory of Diplogenesis, in allusion to the 

 double destination of the effects of use and disuse in 

 inheritance. 



From the preceding considerations we learn that a 

 new character is not inherited unless it is acquired by 

 germ-plasma, as well as by the soma. Should it fail 

 of the former it will not be inherited, although it may 

 appear in the soma. It is also evident that the same 

 character appears in the soma of later generations by 

 virtue of its inheritance by their germ-plasma. Hence 

 should it fail to appear in the adult soma of one gen- 

 eration, it might arise in a later one ; and hence the 

 possibility of atavism, and an alternation of genera- 

 tions. Intermittent stimulus might be followed by in- 

 termittent activity of growth energy. This would be 

 especially apt to occur during the assumption of sex- 

 uality by animals and plants whose reproduction had 

 been performed by cell-division or budding only. And 

 such is the character of most types of alternate gene- 

 rations ; a sexual type alternates with a non-sexual 

 type. The advantages being on the side of sexual re- 



