THE FOUR INSEPARABLE FACTORS OF EVOLUTION. 



29 



i 



Heredity X Ontogeny X Environment X Selection 



Individual, 



lron- 



The use of the multiplication sign ( X ) is a very gross and partly misleading 

 method of expressing the interactions or complexes of conditions which exist. 

 For example, selection operates upon the resultant of the interactions of envi 

 ment, ontogeny, heredity. 



The simplest applications of this formula are as follows: 



Heredity X normal activities of life X normal environment X normal 

 incidence of selection = stability or persistence of type. 



Or again, 



Heredity exhibiting variation X changed or changing activities of life X 

 changing environment X changing incidence of selection = a change of type. 



Another method of expressing the interactions between these four seta of 

 conditions is the following: 



I. 



Heredity. 



II. 



Ontogeny 



III. 

 Environment 



Physical Basis. 



Germ-plasm. 



Germ-plasm and Animate and in- 



IV. 



Selection 

 (Competition). 



somatoplasm. 



animate 

 roundings. 



sur- 



The 



A 



Unknown ("Sum total of the Sum total of the Sum total of the Sum total of the 



Factors, or In- 

 teractions. 



forces and laws 

 operating in the 

 germ plasm. 



laws and forces 

 operating in the 



development of 

 the individual. 



B 



influences of the 

 inorganic and or- 

 ganic surround- 

 ings, including 

 social, racial and 

 non-racial fac- 

 tors. 



struggle for 



existence. 

 Success in ob- 

 taining food, 

 mating ana 

 leaving prog- 

 eny. 



The 



or 



known, 



observable 

 Modes of Ex- 



fression in the 

 henotypes. 



Generally conserv- 

 ative, subject to 

 slow changes. 



of 



Accommodations, Migration, isola- Elimination. 



a 



>> 



Repetitions 



fluctua- 

 " salta- 

 tions," "muta- 

 tions/' etc. 



type, 

 tions, 



modifications, 

 fluctuations, so- 

 mations, gener- 



subject to 

 and 



ally 

 rapid 



treme changes. 



ex- 



t i o n , segrega- 

 tion, insulation 

 changes varying 

 from slow to ex- 

 tremely rapid. 



Struggle for 



e xistence, 

 varying from 

 slow to ex- 

 tremely rapid 



changes. 



The significance of the term interaction was clearly brought out in the writer's 

 first statement of the law in 1907 before the Section of Palaeozoology of the 

 Seventh International Zoological Congress. 1 This statement was as follows: 



>er bv the statement of a law which seems to be axiomatic, although 



l8 !f$L y 1 K nored by biologists. I may term it the law of the four inseparable factors. 



These four factors in the life of organisms are known to us under the terms heredity, ontogeny, 

 environment and selection. The following statement regarding these factors expresses the whole truth : 



1. The life and the evolution of organisms invariably center around processes which, in our 

 observations, are grouped under heredity, ontogeny, environment and selection. 

 "?* a? hav - e been inse P ara ble and interacting from the beginning. 

 " i'u- t u nge mtr °d uce d through any one of these factors causes a change in all. 

 Inis I believe to be the most fundamental law of biology; far more fundamental than the well- 

 Evolution as it Appears to the Paleontologist. Address before the Seventh International Zoo- 

 logical Congress, Section of Paleozoology. Science, N. S., vol. XXVI, No. 674, Nov. 29, 1907, pp. 



744-749. 



Intern. Zool. Congr. (Meet 



