36 PHYSICAL BASIS OF CIVILIZATION 



generation. After this process has continued during 

 a longer or shorter series of generations, and there 

 exists, caeteris paribus, no known cause, which could 

 interfere with its uninterrupted continuation to the 

 end, it must inevitably lead to the utter disappear- 

 ance of the new traits. To the process thus sketched 

 in mere outline, August Weissmann has given the 

 name of "panmixia." 



In this process the factor which counts is the 

 outnumbering of the new trait individuals by the 

 average type, and since this applies equally to all 

 those endowed with any new traits, whether they 

 are favorable or unfavorable to adaptation, it would 

 seem that, other things remaining equal, panmixia 

 must exterminate all new traits in the course of a 

 longer or shorter series of generations. 



It would of course take longer to eradicate favor- 

 able traits, because the individuals endowed with 

 them live longer and reproduce more. They there- 

 fore in the next generation not only increase in 

 numbers, but also in the proportion which their 

 number bears, to the sum total membership of the 

 race. So to speak, however, other things do not 

 remain equal, in such cases. Sexual relations exert 

 an influence which varies according as traits are 

 favorable or unfavorable. For among all higher 

 sexually reproducing animals, both sexes display 

 an unmistakable preference for the more perfect, 

 that is to say, the more adapted specimens of the 

 opposite sex. 



