124 THE EVOLUTION THEOKY 



question — for instance, a long or crooked nose — becomes greater. 

 Certainly an increase of the character may result if in both parents 

 the determinants K are present in excess as compared with the hetero- 

 dynamous determinants K' and K", for in that case there is an 

 increased probability that, through reducing divisions and amphimixis, 

 there will again be a preponderance of the determinants K composing 

 the germ-plasm of the child, and further, that these determinants K 

 will dominate strongly as compared with the few ^^"8. It may thus 

 happen that the long nose of the two parents will give rise to a still 

 longer nose in the child, or that parents of considerable bodily size 

 may have still bigger children, but such increase would be confined to 

 one generation, and would not lead to a permanent increase of the 

 character ; permanent increase cannot depend merely on the number 

 of the determinants K and on their supremacy over their converse, 

 the determinants K' ; it must also depend on their own variation, 

 and this again can depend only on germinal selection and not upon 

 personal selection, although the former can be materially assisted by 

 the latter. 



That inheritance from both parents is only a secondary con- 

 sideration in regard to the increase of a part by artificial selection 

 is made evident by the fact that 'many secondary sexual characters 

 have been modified, altliough the breeder selected only in regard to 

 one parent. Nevertheless in this very domain the greatest results 

 have been achieved ; witness the Japanese breed of cocks with tail- 

 feathers six feet long. This astonishing result has been reached by 

 the strictest selection of the cocks in which the feathers were a little 

 longer than those of other cocks, and the increase in the length of 

 feathers depended — according to our theory— simply on the fact that, 

 by the selection of the determinants which were already varying in 

 the direction of increased length, this process of increase was guarded 

 from interruption by chance unfavourable conditions of nutrition. 

 The continuance of \ariation in the upward direction in which it had 

 already started is not effected directly by personal selection, but is so 

 indirectly, for without this constant fresh intervention of selection 

 the increase would be apt to come to a standstill, or the variation 

 might even take a contrary' direction. There are two other factors 

 operative to which we have not yet given sufficient attention. They 

 are, the multiplicity of tJie ids in ever^- germ-plasm, and sexual repro- 

 duction. 



If — -as we must assume — each germ-plasm is made up of several 

 or many ids, there must be several or many determinants of each part 

 of the organism, for each id contains potentially the whole organism, 



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