46( 



BEAN. 



aud in order to account for this it is necessary to consider the broad 

 head and the long head as unit characters of an allelomorphic pair, with 

 the long head dominant. So the nose of the Iberian is leptorhine, that 

 of the N'egrito platyrhine ; and the nose of type A is platyrhine, therefore, 

 the wide nose is dominant. Many factors, such as environment, natural 

 and sexual selection, the relative number of each type which enter into 

 the amalgamated product, the time during which amalgamation has 

 progressed, etc., exert an influence that must be reckoned with (58). 



The broad nose of the aboriginal persists by sexual selection. The 

 long head of the Iberian with greater mental capacity than the Negrito 

 persists by natural selection. In order to illustrate the amalgamated 

 condition of the Igorots at present I have prepared a simple diagram 

 (fig. 13) to supplement my theory of heredity (5). 



VIII. A SUPPLEMENTARY THEORY OF HEREDITY. 



When dominant and recessive meet in equal numbers the proportion 

 in the second generation is 3 dominant to 1 recessive, and this proportion 

 remains the same in future generations. 



Indi- 

 vid- 

 uals. 



Gener- 

 ation. 



2RR) 



First pa- 

 rental. 



First fil- 

 ial. 



Second 

 filial. 



(DD) (DD) (DR) (DR) 



Third fil- 

 (DR) (DR) (RR) (RR) f jai. 



(DR) (DR) (DR) (DR) 



Hardy (16) has demonstrated by simple mathematics, that a dominant 

 character such as brachydactyly would not tend to increase in a mixed 

 population after the second generation, in the absence of counteracting 

 factors. "Were Mendel's laws continuous in their operation throughout 

 the life history of an endogamous people who represent two elementary 

 species crossed, then one would expect the two to remain distinct and in 

 definite proportions. But suppose Mendel's laws act for only a limited 

 time, after which blending begins, then in the course of time the two 

 elementary species would disappear by becoming absorbed in the blend, 

 and a variable blend would result, the individuals representing every 

 grade of difference between the original types. The blend may even 

 become so perfect as to fonn a new elementary species if time is long 

 enough and inbreeding sufBeiently strong. The new species may be 

 unlike either of the original and not a perfect blend of the two because 

 of dominant factors and through extraneous influences. 



