THE FACTORS OF ORGANIC EVOLUTION. 21 



There are to be recognized two modes of this effect 

 produced by changed conditions on the reproductive system, 

 and consequently on offspring. Simple arrest of develop 

 ment is one. But beyond the variations of offspring arising 

 from imperfectly developed reproductive systems in parents 

 variations which must be ordinarily in the nature of 

 imperfections there are others due to a changed balance 

 of functions caused by changed conditions. The fact noted 

 by Mr. Darwin in the above passage, &quot; that the power of 

 changed conditions accumulates; so that two, three, or 

 more generations must be exposed to new conditions before 

 any effect is visible,&quot; implies that during these generations 

 there is going on some change of constitution consequent 

 on the changed proportions and relations of the functions. 

 I will not dwell on the implication, which seems tolerably 

 clear, that this change must consist of such modifications 

 of organs as adapt them to their changed functions ; and 

 that if the influence of changed conditions &quot; accumulates,&quot; 

 it must be through the inheritance of such modifications. 

 Nor will I press the question What is the nature of the 

 effect registered in the reproductive elements, and which 

 is subsequently manifested by variations ? Is it an effect 

 entirely irrelevant to the new requirements of tlue variety ? 

 Or ?s it an effect which makes the variety less fit for the 

 new requirements ? Or is it an effect which makes it more 

 fit for the new requirements? But not pressing these 

 questions, it suffices to point out the necessary implication 

 that changed functions of organs do, in some way or other, 

 register themselves in changed proclivities of the repro 

 ductive elements. In face of these facts it cannot be denied 

 that the modified action of a part produces an inheritable 

 effect be the nature of that effect what it may. 



The second of the remarks above adverted to as made 

 by Mr. Darwin, is contained in his sections dealing with 

 I correlated variations In the Oriyin of Species, p. 114, 

 he says 



