300 THE FOUR INSEPARABLE FACTORS OF EVOLUTION. 



(a) Under what conditions are new characters or modifications of character 

 initiated? 



(6) Do such new characters appear to be initiated by one factor or simul- 

 taneously by two or more factors? 



Many of the conclusions which have hitherto been drawn, especially by field 

 naturalists as to the initiation of new characters appear to assume that it is 

 easy matter to determine the point of initiation. As a matter of fact it is often 

 extremely difficult to determine the point of initiation. 



This raises the distinction between initiation and genesis. 



an 



1. Initiation and Genesis. 



Initiation and genesis of characters are different phenomena. Initiation or 

 the series of causes which precede the genesis of a new character may lie either 

 in environment, in ontogeny, in selection, or in heredity. Somatic origins or 

 genesis may be found in ontogeny, as expressed in the word somatogenesis. 

 Blastic origins, or true genesis can occur only in heredity or in blastogenesis. 



If each factor is conceived as influencing every other, the question in what 

 part of the circle or chain of causes a disturbance begins which results in the 

 appearance of a new character is often a very difficult one. We must not confuse 

 a new character with one which is recalled from a latent condition by the revival 

 of an ancestral environment. For example, the under surfaces of flat fishes is 

 apparently white, or unpigmented; the action of sunlight on this white surface, 

 however, reveals the fact that the ancestral pigmented character still persists 

 and may be called forth as a reaction to sunlight. This is not a new character, 

 it is simply a revival of a character which is latent not only in heredity, but 

 in ontogeny. 



The question of initiation is also difficult in heredity. For example, a 

 "mutation of De Vries" is apparently initiated in heredity, but the experiments 

 of MacDougal, Tower, and others, show that initiation is to be sought in the 

 influence of environment on the germ cells. Similarly we may look for other 

 experiments which will prove that certain saltations may find their initiation in 

 ontogenic changes which reflect the germ cells, these in turn being due to environ- 

 mental changes through a chain of causation. The inquiry as to initiation will 

 in a measure harmonize the apparent discrepancies between the results obtained 

 by those extreme observers (p. 282) who have centered their attention on a 

 single factor to the exclusion of the consideration of other factors. 



From the above considerations we may express the general law somewhat as 

 follows : 



In a state of nature at no stage is any one of the factors released from the operation 

 of all the others. Every animal represents its heredity visibly expressed in and 



ifluenced by its ontogeny, its environment, and 



The normal balance 



of life in an organism being analogous to the normal balance of nature, the 

 disturbance of one of the factors produces a disturbance in all. 



