i.l VARIATION AND HEREDITY 83 



nascent parts of this organism enjoy a kind of immunity 

 as regards C: the same part will then undergo alteration 

 in the new organism, because it happens that the develop- 

 ment of this part is alone subject to the new influence. 

 And, even then, the part might be altered in an entirely 

 different way from that in which the corresponding part 

 was altered in the generating organism. 



We should propose, then, to introduce a distinction 

 between the hereditability of deviation and that of char- 

 acter. An individual which acquires a new character 

 thereby deviates from the form it previously had, which 

 form the germs, or oftener the half-germs, it contains 

 would have reproduced in their development. If this 

 modification does not involve the production of sub- 

 stances capable of changing the germ-plasm, or does not 

 so affect nutrition as to deprive the germ-plasm of certain 

 of its elements, it will have no effect on the offspring of 

 the individual. This is probably the case as a rule. If, 

 on the contrary, it has some effect, this is likely to be due 

 to a chemical change which it has induced in the germ- 

 plasm. This chemical change might, by exception, bring 

 about the original modification again in the organism which 

 the germ is about to develop, but there are as many and 

 more chances that it will do something else. In this 

 latter case, the generated organism will perhaps deviate 

 from the normal type as much as the generating organism, 

 but it will do so differently. It will have inherited deviation 

 and not character. In general, therefore, the habits 

 formed by an individual have probably no echo in its 

 offspring; and when they have, the modification in the 

 descendants may have no visible likeness to the original 

 one. Such, at least, is the hypothesis which seems to 

 us most likely. In any case, in default of proof to the con- 

 trary, and so long as the decisive experiments called for 



