424 THE GRAMMAR OF SCIENCE 



(/;) Endogamic mating, or mating within the family, 

 brood, or clan. 



(c) Homogamic mating, or the mating of like with 

 like, the two mates not being of the same brood, or not 

 necessarily so. I also term this assortative mating. 



(d) Apolegamic^ mating, or preferential mating. This_ 

 is sexual selection in the narrower sense of Darwin. In this 

 case either (i.) certain males by their superior force, or their 

 superior attraction, monopolise the females, thus leaving 

 other males wholly or partially without mates ; or (ii.) 

 certain females are wholly or partially rejected by the 

 males owing to want of vigour or inferior attraction.^ 



(e) Heterogamic mating, or the mating of unlikes. 

 Under this head I include the mating of unlike forms in 

 the same race, especially developed for mutual fertilisation. 



As opposed to all these forms of selective mating, we 

 have : — 



(/) Pangamic mating, or the mating at random of all 

 members within the race. The unions may be seasonal 

 or permanent, but no racial selective tendency as opposed 

 to individual caprice can be distinguished in these 

 unions. 



If natural selection be at work, all the forms (a) to (e) 

 of mating can have great influence on differentiation — it 

 is only (/) which would check it. 



To the importance of autogamic and endogamic mating 

 in raising barriers to intercrossing I have already referred 

 (p. 417). On the wide and interesting subject of hetero- 

 gamic mating, the reader should consult Darwin's works, 

 T/ie Effects of Cross and Self-fertilisation in the Vegetable 

 Kingdom^ and On the differe?it Forms of Flozuers on Plants 

 of the same Species. With their numerous statistics of 

 the relative fertility of heterogamic and homogamic 



(iii.) Hetairic or Adelphic ; the latter corresponding to what I should under- 

 stand by endogamy proper. 



1 For apolego-gamy, from d7roX^7a;, I pick out, say no to, refuse. 



2 This occurs especially in populations where the female is in a preponder- 

 ance. In the case of mankind, over or under sexual attraction, and over 

 or under sexual inclination in the woman, may lead to her exclusion from that 

 form of mating under which normal reproduction is alone possible. 



