306 THE FOUR INSEPARABLE FACTORS OF EVOLUTION. 



operates in a manner adapted to new conditions and through the interaction 

 of forces which are entirely unknown and incomprehensible to us. 



The formula of both initiation and genesis in heredity will be as follows • 



H 1 X o x e x s. 



The above will be the formula of an internal perfecting principle operating 

 independently of initiation through the action of environment or of ontogeny. 

 In our opinion there is no evidence for such an internal perfecting principle. 



SUMMARY. 



Investigation and experiment may proceed to test two working hypotheses: 

 first, that while inseparable from the others each factor may under certain 

 conditions become an initiative or leading factor ; second, that in complex organ- 

 isms one factor may be initiative in one group of characters while another factor 

 may at the same time be initiative in another group of characters, the inseparable 

 action bringing about a continuously harmonious result. 



The following general summary may be made as to our conception of the 



interoperation of the several factors : 



1. In all conditions of life the four factors work together continuously like 

 the forces of four magnetic fields although the readjustments are so infinite that 

 analogy with any physical phenomenon such as the above cannot express the 

 interaction. 



2. Each of these factors has its specific sphere of action in which the modes 

 of externally observed phenomena are apparently supreme; for example, we 

 recognize the supreme action of selection and of elimination in certain cases, 

 in other cases the supreme action of the direct influences of environment or the 

 supreme action on ontogenic modifications of structure caused by certain habits, 

 or the still more profound and permanent changes which reflect disturbances in 

 heredity. 



3. Under certain natural as well as artificial conditions a supreme factor 

 may arise operating more strongly than the others, or two factors may simul- 

 taneously become supreme and take the initiative in instituting a change. Thus 

 there are changes of the first order (t. e., initiative), and changes of the second 

 order (i. e., those which follow or are coordinated with the former; compare 

 Cramp ton). Alter one factor ever so slightly and the entire balance between 

 the four may be disturbed, a disturbance comparable to the disturbance in the 

 balance of nature. 



4. The changes which are initiated in environment and ontogeny sooner or 

 later become reflected or expressed in heredity. 



5. The causal relation, if such exists, between the real genesis of characters 

 in heredity and the factors of ontogeny and environment still remains as the 

 chief field of investigation in biology. 



