PLANT HYBRIDIZATION BEFORE MENDEL 251 



contribution of each several ancestor to the total heritage of the 

 offspring." 



In this contribution Galton remarks that the truth of the sta- 

 tistical law of heredity, which had been stated "briefly and with 

 hesitation" in his "Natural Inheritance," because "it was then 

 unsupported by sufficient evidence," having been now found to 

 hold for a particular case, there are, as he says, "strong grounds 

 for believing it to be a general law of heredity." (p. 401). Gal- 

 ton at first in this connection, began "a somewhat extensive series 

 of experiments with moths," which, however, failed owing to the 

 diminishing fertility of successive broods, and the disturbing ef- 

 fects of differences in food and environment. Consequently, as he 

 says, "no statistical results of any consistency or value could be 

 obtained from them." (p. 402.) While engaged in planning an- 

 other extensive experiment with small, fast-breeding mammals, 

 Galton 



". . . became acquainted with the existence of a long series of records, 

 preserved by Sir Everett Millais, of the colours during many successive 

 generations of a large pedigree stock of Basset hounds, that he origi- 

 nated some twenty years ago, having purchased ninety-three of them on 

 the continent for the purpose. These records afford the foundation upon 

 which this memoir rests." (p. 402.) 



The "law," as briefly stated is, 



". . . that the two parents contribute between them on the average, 

 one-half or (0.5) of the total heritage of the offspring ; the four grand- 

 parents, one-quarter or (0.5)-, the eight great-grandparents one-eighth 

 or (0.5)"*, etc., which being equal to l, accounts for the whole heritage." 

 (p. 402.) 



"The same statement may be put into a different form, in which a 

 parent, grandparent, etc., is spoken of without reference to sex, by say- 

 ing that each parent contributes on an average, one-quarter or (0.5)^, 

 each grandparent one-sixteenth or (0.5)'*, and so on, and that generally 

 the occupier of each ancestral place in the nth degree, whatever be the 

 value of n, contributes (0.5)^" of the heritage." (p. 402.) 



Galton refers to sex-limited inheritance, although not precisely 

 in the manner now current, in the following statement: 



"The neglect of individual prepotencies is justified in a law that avow- 

 edly relates to average results ; they must, of course, be taken into ac- 

 count when applying the general law to individual cases. No difficulty 

 arises in dealing with characters that are limited by sex, when their 

 equivalents in the opposite sex are known, for instance in the statures of 

 men and women." (p. 402.) 



