THE METHOD OF CREATIOI^ OF ORGANIC FORMS. 203 



causes have originated modifications of structure, we give the 

 adaptive principle too much to do. I have made the same objec- 

 tion to the theory of natural selection. It is true that an applica- 

 tion to a purpose is involved in the present theory of the "location 

 of growth-force "' ; but in point of fact, a large number of non- 

 adaptive characters are accounted for by it. These are the rudi- 

 mental and transitional ones which mark the successive steps pre- 

 liminary to the completion of an adaptive structure ; second, those 

 produced by deficiency of growth-force in less favored regions of 

 the body ; and third and fourth, phenomena consequent on general 

 deficiency and excess of growth-force. 



And it may be said in conclusion that if the three principles, 

 or if use especially, should be found to be inadequate to the service 

 here demanded of them, it may be at least said that they, or the 

 last named, constitute the only controllers of growth-force to any 

 degree at all with which we are acquainted. 



IV. 0]S^ GRADE-INFLUENCE. 



The object of the present section is the attempt to discuss how 

 the influence of effort and use on the parent is placed in a position 

 to be inherited by the offspring. 



A. Of the nature of Grade-Influence. 



In the first place, it is necessary to note the definition and char- 

 acter of grade-influence. 



a. Growth- force uninfluenced by grade-influence simply adds 

 tissue either («) in enlarging size, or {b) in replacing waste. It 

 does this by repeating the cell, by division, in localities which have 

 already assumed their specific form. This form of growth-force 

 may persist throughout life, but with diminished energy in age. 



/3. Grade-influence directs growth-force in building up the tis- 

 sues into organs, and constructs the parts of the body successively 

 to completion, the result expressing the type or grade of the ani- 

 mal or plant. Its energy terminates with maturity, except in 

 cases of periodical reproduction of sexual ornaments of the male 

 (birds, deer), where it continues throughout life, appearing at 

 regular intervals. 



But it has occurred in acceleration that instead of a siniiile repe- 

 tition of tlie ultimate histological element of an organism, in add- 

 ing to its amount, it adds a completely organized part of the struct- 



