264 THE EVOLUTION THEORY 



highest plants and animals, amphimixis now means an augmentation 

 of the organism's power of adaptation to the conditions of its life, 

 since it is only through amphimixis that simultaneous harmonious 

 adaptation of many parts becomes possible. It effects this by the 

 mingling and constant recombination of the germ -plasm ids of different 

 individuals, and thus gives the selection-processes the chance of favour- 

 ing advantageous variational tendencies and eliminating those which 

 are unfavourable, as well as of collecting and combining all the varia- 

 tions which are necessary for the further evolution of the species. 

 This indirect influence of amphimixis on the capacity of organisms 

 for surviving and being transformed is the fundamental reason for its 

 general introduction and for its persistence through the whole known 

 realm of organisms from unicellulars upwards. 



The reason for its first introduction among the lower forms of life 

 must have been a direct effect which had a favourable influence on the 

 metabolism, and this is so far coincident with the subsequent import 

 of amphimixis, inasmuch as it may be regarded not only as a height- 

 ening of the power of adaptation, but as an immediate and direct 

 increase and extension of the power of assimilation. In any case, 

 amphimixis is not necessary to the actual preservation of life itself, 

 but it does bring about a wealth and diversity of organic architecture 

 which without it would have been unattainable. 



If amphimixis has been abandoned in the course of phylogeny 

 by isolated groups of organisms, this has happened because other 

 advantages accrued to them in consequence, which gave them greater 

 security in the struggle for existence ; but it must be admitted that 

 they thereby lost their perfect power of adaptation, and that they 

 have thus bartered their future for the temporary securing of their 

 existence. 



In addition to this variational influence, amphimixis has also 

 played a part in the evolution of sharply defined organic types, espe- 

 cially of specific tj'pes ; but of this we shall have more to say later on. 



Digitized by Microsoft® 



