SPONTANEOUS GENERATION AND EVOLUTION : CONCLUSION 375 



the most favourable way and rejecting those which vary unfavourably, 

 but that there is an analogous struggle between the parts of these 

 uidividuals, which, as Wilhelm Roux showed, effects the adaptation 

 of the parts to their functions, and that this struggle must be assumed 

 to occur even between the determinants and biophors of the germ- 

 plasm. There is thus a germinal selection, a competition between the 

 smaller and larger particles of the germ-plasm for space and food, 

 and that it is through this struggle that there arise those definitely 

 and purposefully directed variations of the individual, which are 

 transmissible because they have their seat in the immortal germ- 

 plasm, and without which an adaptation of individuals in the sense 

 and to the extent in which we actually observe it would be altogether 

 inconceivable. I have endeavoured to show that the whole evolution 

 of the living world is guided essentially by processes of selection, 

 in as far as adaptations of the parts to one another, and of the whole 

 to the conditions of life, cannot be conceived of as possible except 

 through these, and that all fluctuations of the organism, from the 

 very lowest up to the highest, are forced into particular paths by this 

 principle, by 'the survival of the fittest.' This ends the whole 

 dispute as to whether there are indifferent ' characters ' which have 

 no influence on the existence of the species, for even the characters 

 most indifferent for the ' person ' would not exist unless the 

 germinal constituents (determinants) which condition them had 

 been victorious in the struggle for existence over others of their 

 kind, and even the ' indifferent ' characters, which depend solely upon 

 climatic or other external influences, owe their existence to processes 

 of germinal selection, for those elements of the determinants concerned 

 were victorious which throve best under such influences. But should 

 variations thus produced by external influence increase so far that 

 they become prejudicial to the survival of their bearers, then they 

 are either set aside by personal selection or, if that be no longer 

 possible, they lead to the extinction of the species. Thus the multitude 

 of small individual variations, which probably occur in every species, 

 but which strike us most in Man — the differences in the development 

 of mouth, nose, and eyes, in the hair, in the colour of skin, &c., 

 as far as they are without significance in the struggle for existence — 

 depend upon processes of germinal selection, which permitted the 

 greater development of one group of determinants, or of one kind 

 of biophor in one case, of another in another. The proportionate 

 strength of the elements of the germ-plasm is not readily lost at 

 once, but is handed on to successive generations, and thus even these 

 ' indifferent ' characters are transmitted. 



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