1909.] 



Correlations of a Mendelian Population. 



229 



The following table illustrates the percentages of dominant charactered 

 offspring when we selected an ancestor of given character : — 



Ancestor. 



Percentage of dominants in offspring. 



P = 



2q. 



P = 



= ?• 



1 = 



2p. 



Dominant. 



Eecessive. 



Dominant. 



Eecessive. 



Dominant. 



Eecessive. 





91 7 



66 -7 



83 -3 



, 50-0 



57-8 



33 -3 





90 -3 



77 -8 



79 -2 



62 -5 



56 -7 



44 -4 



3rd parent 



89 -6 



83 "3 



77 -1 



68 -7 



56 -1 



50 -0 



4th parent 



89 -2 



86 1 



76 -0 



71 -9 



55 -8 



52-8 



5th parent 



89 -1 



87 -5 



75 -5 



73 -4 



55 -7 



54 -2 





89 -0 



88-2 



75 -3 



74 -2 



55 -6 



54 -9 





88 -9 



88 -9 



75 -0 



75-0 



55 -6 



55 -6 



It will be clear that the difference of the percentage of dominants in the 

 offspring according as a parent, grandparent or great grandparent was 

 dominant or recessive in somatic character is quite marked ; and only as we 

 approach the higher ancestry, where the correlation is growing very weak, 

 does the percentage difference grow imperceptible. 



(8) That ancestry does not matter if we know the gametic constitution of 

 the parents, that it does matter if we only know the somatic character of 

 the parents appears to be the solution of one of the difficulties which some 

 have found between the Mendelian and biometric methods of approaching 

 the subject. 



There is, however, I venture to think, another aspect of these results 

 which is worthy of fuller consideration. Namely, the fairly close accordance 

 now shown for the first time to exist between the ancestral gametic 

 correlations in a Mendelian population and the observed ancestral somatic 

 correlations suggests that the accordance between gametic and somatic 

 constitutions is for at least certain characters possibly more intimate than 

 is expressed by an absolute law of dominance. If (Aa) were a class, or 

 possibly on a wider determinantal theory a group of several classes, marked 

 by an individual somatic character — not invariably identical with the 

 somatic character of (AA) — there would be little left of contradiction 

 between biometric and Mendelian results as judged by populations sensibly 

 mating at random. It is the unqualified assertion of the principle of 

 dominance which appears at present as the stumbling block. 



VOL. lxxxi. — B. 



E 



