THE FACTS AND FUNCTION OF SEX 35 



study biological problems from a standpoint of i heir 

 own, and who have frequently disposed of various 

 hypotheses widely held, have lately devoted their 

 attention to the facts of sexual selection,^ and, on 

 this occasion, have gone far to confirm and supple- 

 ment the conclusions of Darwin. They have shown 

 that, in all cases hitherto examined, there is a prin- 

 ciple of homogaviy, the mating of like with like. 

 It hardly needs saying that this observed fact of 

 sexual reproduction consorts completely with the 

 view that amphimixis is a means of ensuring the 

 stability of the species. The discovery of the fact 

 of homogamy is absolutely incompatible with Weis- 

 mann's interpretation of amphimixis, but most sig- 

 nally confirms this new interpretation of the facts of 

 sex, which has been reached by quite another route. 

 Let us now make note of Mr. Reid's chief points; 

 previously reminding ourselves of the meaning of the 

 terms progressive and regressive as applied to varia- 

 tions. We have seen that amphimixis is not a cause 

 of progressive variations. On the contrary, there is 

 much evidence which shows that '* bi-parental repro- 

 duction tends to eliminate the characters in which 

 parents differ, and to leave unafi'ected those in which 

 they agree." It is a matter of common observation 

 that exceptional peculiarities of parents tend to dis- 

 appear. But if both parents are tall and dark, say, 

 or short and fair, these variations tend to be per- 

 petuated l)y amphimixis. There is no evidence 

 that bi-parental reproduction is connected with pro- 

 gressive variations as cause and effect ; whenever it 



1 This very import :uil subject is dealt with in Cliap. vi. of tho 

 volume ou " Orgauic Evolution." 



