1912.] NATURAL SCIENCES OF PHILADELPHIA. 145 



The interopcration of the four factors may be represented sym- 

 bolically by the letters E. 0. H. S. 



Returning to our original questions as to: (1) the origin and (2) 

 the transformation of characters, we first observe that there is the 

 following genera! relation: 



External Initiation Environment, E. 



Internal Genesis Ontogeny, O. 



Heredity, H. 



External Fixation Selection, S. 



All phenomena involving either the origins or the transformations 

 of character may be conveniently represented by the use of formula 

 composed of E, O, H, S. Similarly, all interpretations of changes of 

 character should be made with this interopcration of the factors in 

 mind. For example, in the matter of continuity or discontinuity, 

 we find that E, 0, H, S, must all be considered. Thus the " con- 

 tinuity in Heredity" of the germ plasm is no more vital than the 

 "continuity in Ontogeny," or "continuity in Environment," or 

 "continuity in Selection," because change or discontinuity in any 

 one of these three latter factors, E, 0, S, immediately or finally 

 results in transformation of character in H. 



Again, in experimental as contrasted with natural conditions we 

 observe the following: 



In experiment, 



Selection may be removed or altered. 

 Environment may be altered. 

 Ontogeny may be altered. 

 Heredity may be affected through E, 0, S. 



On the contrary, in nature, 



E, O, H, S, are constantly interoperative. 



Thus the tetraplasic law, first conceived in 1905, first expressed 

 in 1908, may now be expressed in 1912 as follows: The life and 

 evolution of organisms continuously centre around the processes which 

 we term Heredity, Ontogeny, Environment, and Selection; these have 

 been inseparable and interacting from the beginning; a change intro- 

 duced or initiated through any one of these factors finally results in a 

 genetic change. 



The conception of the individual, therefore, may be expressed in 

 the following diagram A: 



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