194 GENERAL EVOLUTION. 



parents, and become energetic in the growing foetus of the next 

 generation. However little we may understand this mysterious 

 process, it is nevertheless a fact. Says Murphy, '' There is no act 

 which may not become habitual, and there is no habit that may 

 not be inherited." Materialized, this maybe rendered — there is 

 no act which does not direct growth -force, and therefore there is 

 no determination of growth-force which may not become habitual ; 

 there is, then, no habitual determination of growth-force which 

 may not be inherited ; and, of course, in a growing foetus becomes 

 at once energetic in the production of new structure in the direc- 

 tion inherited, which is acceleration. 



But if the forces converted into growth-force are derived from 

 without the animal organism, whence and what the agency by 

 which the acceleration or retardation of the latter is inherited 

 from the parent ? A few suggestions only on this head can be 

 made in the fourth section. 



III. THE LAAV OF USE ASTD EFFORT. 



Up to this point we have followed paths more or less distinctly 

 traced in the field of nature. The positions taken appear to me 

 either to have been demonstrated or to have a great balance of 

 probability in their favor. In the closing part of this paper I 

 shall indulge in more of hypothesis than heretofore. 



Since repetitive addition only produces identical results in 

 archetypes, and each effort produces results more and more unlike 

 its predecessor as structure becomes specialized, it becomes im- 

 portant to examine into the influences which have originally 

 modified the repetitive efforts successively, producing structures 

 more or less different in detail in the second generation from 

 those of the parents, in acceleration, or the reverse, in retarda- 

 tion. 



Going further back, the question arises, why a simple exhibi- 

 tion of repetition (e. g., cell-division) should be converted into a 

 complex or duplicated repetitiotf (e. g., jointed ray). This, it has 

 already been stated, is one consequence of increased amount of 

 the growth-force. 



We then seek explanation of the main question, as to what de- 

 termines the location of this additional or new growth-force. 

 (Div. A.) 



Lastly, why the total amount of this force should change in a 

 given individual or part of an individual. (Div. B.) 



