LAW OF ANCESTRAL INHERITANCE 327 



spring and their parents, their grandparents, and so on backwards, 

 He finds that the correlation between offspring and parent is 

 about o"5, between offspring and grandparent 0-33, between off- 

 spring and great-grandparent 0"22. These figures indicate the 

 degree of resemblance, in respect of a character measured, between 

 offspring and an ancestor of each generation. From these he 

 has worked out the average ancestral contributions, and he has 

 been led to conclude that the series 0*6244, 0-1988, 0-0630, etc., 

 is more accurate than Galton's series 0-5, 0*25, 0-125, erc - 



Summary. — Galton formulated his Law of Ancestral In- 

 heritance as follows : " The two parents contribute between 

 them on the average one-half or (0-5) of the total heritage of 

 the offspring ; the four grandparents, one-quarter, or (o - 5) 2 ; 

 the eight great-grandparents, one-eighth, or (o - 5) 3 , and so on. 

 Thus the sum of the ancestral contributions is expressed by the 

 series [(0-5) -f (o - 5) 2 -f (o - 5) 3 , etc.], which, being equal to 1, 

 accounts for the whole heritage " (1897, p. 402). 



But it is quite legitimate to accept the general idea of this 

 Law without accepting the fixity of the fractions of partial in- 

 heritance which it expresses. 



Mr. G. Udny Yule states the law of ancestral heredity in the 

 most general way possible when he says : " This law, that the 

 mean character of the offspring can be calculated with the more 

 exactness, the more extensive our knowledge of the corresponding 

 characters of the ancestry, may be termed the Law of Ancestral 

 Heredity " (1902, p. 202). 



Prof. Weldon (1902) states the law of ancestral inheritance in 

 the following terms : " The degree to which a parental character 

 affects offspring depends not only upon its development in the 

 individual parent, but on its degree of development in the ancestors 

 of that parent." Mr. Yule suggests that, instead of the word 

 " affects," which to some extent implies a direct physical in- 

 fluence, it would be more accurate to read " serves as a basis 

 for estimating the character of," 



