THE REPRODUCTIVE FACTOR IN EVOLUTION. 301 



emphasised the organism's inherent power of self-improvement, 

 the moulding influence of new needs, desires, and exertions, 

 and the indirect action of the environment in evoking these. 



To Treviranus (writing in 1802-31) — a biologist too much 

 neglected both in his lifetime and since — organisms appeared 

 almost indefinitely plastic, especially however under the direct 

 influence of external forces. His keen analysis of possible 

 factors did not fail to recognise, — what Brooks, Galton, Weis- 

 mann, and others have since elaborated, — that the union of 

 diverse sexual elements in fertilisation was in itself a fountain 

 of change. " Every form of life," he says, " may have been 

 produced by physical forces in either of two ways, either from 

 formless matter, or by the continuous modification of form. 

 In the latter case, the cause of change may be either in the 

 influence of the heterogeneous male reproductive matter on the 

 female germ^ or in the influence of other potencies after 

 generation." 



His contemporary Lamarck (writing in 180 1-9) — of greater 

 posthumous fame — fought in poverty like a hero for the evolu- 

 tionary conceptions of his later years. He is well known to 

 have emphasised the importance of changed conditions in 

 evoking new needs, desires, and activities, urging at the same 

 time the perfection wrought upon organs by increased practice, 

 and conversely the degeneration which follows as the nemesis 

 of disuse. Evolution seemed to him to be due to the inter- 

 action of two fates, — an internal progressive power of life ; and 

 the external force of circumstances, encountered in the twofold 

 struggle with the inanimate environment and with living 

 competitors. 



Among the philosophers too, and especially in the minds 

 of those who had been disciplined in physical or historical 

 investigations, the speculations of the ancients were ever taking 

 fresh form, gaining moreover in concreteness. Thus Kant 

 viewed the evolution of species mainly in terms of the 

 mechanical laws of the organism itself, but allowed also for 

 the influence of environment, noted the importance of selection 

 in artificial breeding, and, like such ancients as Empedocles 

 and Aristotle, had glimpses of the notion of the struggle for 

 existence. The same idea is more distinct in Herder's 

 " Philosophy of History," where, probably under Goethe's 

 influence, he speaks of the " struggle, each one for itself, as if 

 it were the only one," of the limits of space, and of the gain to 



