VARIATION 419 



and that the deviations to which they are subject on account of 

 inequalities of nutrition are as a rule so infinitesimal that their 

 effect is unnoticeable. 



These deviations are nevertheless of great significance, for 

 they form the material fro))i which the visible itidividiial varia- 

 tions are produced by means of amphimixis together with selec- 

 tion ; and new species arise by the increase and combination of 

 these variations. 



The hypothesis that the germ-plasm consists of ids is quite 

 indispensable in this case Every determinant is represented 

 in the germ-plasm as many times as there are ids in the latter, 

 for every id contains all the kinds of determinants. The deter- 

 minant N, for example, is represented a hundred times if the 

 germ-plasm consists of a hundred ids. Most of these ids must 

 differ slightly from one another, for in the course of generations 

 they are continually brought together in new combinations by 

 the process of amphimixis. On the occurrence of this process, 

 however, the diversity of the ids persists, even if we go back to 

 the origin of the multicellular forms, or of the unicellular ones 

 from the primordial organism. A condition in which all the ids 

 could be considered similar is never found ; in fact, as already 

 stated, the dissimilarity of individuals must be traced to the 

 primordial orgatiisin, at a period when neither the process of 

 amphimixis nor idioplasm had come into existence, and in which 

 every individual organism derived its individuality directly from 

 the dissimilarity of external influences. From these organisms 

 the dissimilarity was transmitted to the unicellular forms, which 

 cannot all have originated from one primordial organism, but 

 each species must have arisen polyphyletically from a large 

 number of similarly modified organisms. This point has often 

 been misunderstood, and I have been asked to explain, for 

 example, how the adaptations of flowers, fruits, and seeds in 

 Phanerogams, could have been derived from a combination of 

 characters acquired by the shapeless primordial ancestors. The 

 characters were not i7iJierited from the primordial beings^ but 

 variability, or the dissimilarity of individuals . 



We might, however, be inclined to believe that external influ- 

 ences must affect all homologous determinants of a germ-plasm 

 in the same way, and must cause them to vary ; but this would 

 be erroneous. 



Since reproduction is connected with amphimixis in the 



