90 THE EVOLUTION OF MAN. 



every organism is the product of the co-operation of two 

 contrary constructive forces, or formative tendencies. One, 

 the internal formative tendency, " the centripetal force," is 

 that of the type, or " the tendency toward specification," 

 which constantly aims at maintaining uniform the organic 

 forms of the species in the series of generations. This is 

 Heredity. The other, the external formative tendency, 

 " the centrifugal force," is variation, or " the tendency 

 toward metamorphosis," which acts, through the continual 

 changes made in the external conditions of their existence, 

 so as continually to vary the species. This is Adapta- 

 tion. 



In this significant conception, Goethe very nearly con- 

 ceived the two great mechanical factors, Heredity and Adap- 

 tation, which are, we assert, the most important efficient 

 causes of the formation of species. For example, he says, 

 that "at the foundation of all organization there is an 

 original intrinsic kinship " (which is Heredity) ; " the variety 

 of forms, however, is due to the conditions of relation 

 necessarily held to the external world, on account of which 

 we may properly assume, for the purpose of explaining the 

 present forms, which are both varied and unvaried, that 

 there was diversity, originally and simultaneously, and that 

 a progressive transformation is continually going on" 

 (which is Adaptation). 



In order rightly to appreciate Goethe's morphological 

 views it is, however, necessary to grasp the connection 

 between the whole peculiar course of his monistic study of 

 nature and his pantheistic conception of the world. Most 

 significant in this respect is the lively and warm interest 

 with which he followed the efforts which the French 



