CHAPTER IV 



FAILURE OF THE CLASSICAL FACTORS TO EXPLAIN THE 

 IMMEDIATE AND DEFINITIVE * CRYSTALLISATION ' OF 

 THE ESSENTIAL CHARACTERISTICS OF NEW SPECIES 

 AND NEW INSTINCTS 



IT appears then, that whether we consider physical 

 characteristics or instincts, both seem to be immutable. 

 They may develop or atrophy, and may vary within 

 narrow limits, but these changes are always changes of 

 detail, never of essentials. This truth had been clearly 

 brought out long before by the researches of naturalists : 

 De Vries brought to it the support of direct experiment. 

 He reduced it to the following law: ' New species become 

 stable immediately.' This involves a new and serious 

 objection to classical transformism. 



If new species appear abruptly and immediately 

 become stable, the theory of innumerable and slow 

 transformations under selective or adaptive influences 

 is definitely ruined as a general and essential theory. 



The evolutionary question is no longer one of a 

 vast accumulation of infinitesimal changes bringing 

 about the formation of new species ; but of considerable 

 and abrupt changes revealing themselves by the rapid 

 appearance of species that become permanent as soon 

 as they have appeared. 



This is an immense revolution in naturalistic philos- 

 ophy. The four difficulties which have just been 

 reviewed are of the naturalistic order. Before passing to 

 the fifth, which is of a totally different kind, and of a 

 metaphysical nature, I will beg the reader who may not 



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