104 HEREDITY AND SELECTION IN SOCIOLOGY 



fact that, through its agency, organic defects in either of the 

 parental individuals are remedied ; thus, an individual A may 

 possess stronger digestive biophors than an individual B, who, 

 on the other hand, may possess stronger nervous biophors than A. 

 The product of the mingling of the germ-plasms A and B will 

 thus profit by the better digestive apparatus of A and the stronger 

 nervous system of B. The direct individual advantage is more 

 obvious in plastogamy — i.e., the mingling of the protoplasm, not 

 of the nuclei, of two cells, as in the case of certain Protozoa. It 

 is obvious that if one organism suffers from defective secreting 

 biophors, the other from defective digestive biophors, the con- 

 jugation and subsequent mingling in a single individual must be 

 beneficial to both, provided the one organism possesses what the 

 other lacks.^ 



The direct value of amphimixis to the individual, as in cases of 

 plastogamy, must have been the fundamental reason for its 

 introduction into the organic world. But, leaving the question 

 of the primary origin of amphimixis, which has no practical im- 

 portance for us in this study, let us turn to amphimixis in its 

 relation to the human species. 



The human species, as far as the deeper traits of its constitu- 

 tion are concerned, is constant ; but this constancy does not 

 prevent a slow and steady variation, especially of the more passive 



1 Plastogamy, as one of the stages leading on to amphimixis, is a highly 

 interesting phenomenon, which was first observed in amoeboid organisms. 

 About fifty of these microscopic animals were observed forming a sort of 

 nest, lying close to one another, without joining together. Although no 

 apparent result foUows from this " cytotropism," or mutual attraction of 

 identical cells — a phenomenon first studied by Wilhelm Roux — it is 

 obvious that some advantage must result to the individuals thus brought 

 together. Cytotropism may help us to understand the evolution of the 

 phenomena of the blending of nuclei (amphimixis). 



Weismann describes a slightly higher stage as plastogamy — ^namely, 

 the case of certain Protozoa in which there is a minghng of the cytoplasm, 

 and not of the nuclei. There is, however, no essential difference between 

 this blending of the cytoplasm and the simple cytotropism observed among 

 the Amoebae. 



