HEREDITY 185 



words, although for an understanding of the cliaraeter of the 

 evidence on which it is based, and for an appreciation of its wliole 

 significance some full account of it, preferably Gait on 's own 

 statement and discussion of it in his memoir entitled "The 

 Average Contribution of Each Several Ancestor to tlie Total 

 Heritage of the Offspring,'' published in 1897, should be read. 

 From a study of the carefully kept i)edigree book of the kennels 

 of the Basset Hounds Club, with records extending through 

 twenty-two years, and a study of inlieritance in the British 

 Peerage made possible by the comi)lete genealogic records 

 kept for these families, together with a consideration of va- 

 rious other less detailed but at least helpful records of inher- 

 itance, Galton formulated the statement that any organism of 

 bisexual parentage derives one half its inherited qualities from 

 its parents (one fourth from each parent), one fourth from its 

 grandparents, one eighth from its great-grandparents, and so 

 on. These successive fractions, whose numerators are one and 

 whose denominators are the successive powers of two, adtled 

 together equal one or the total inheritance of the organism: thus 



Ki + i+TV+3V+^V+ . . . . =1. 



The English mathematician and natural philosopher, Karl 

 Pearson, has made computations showing that Galton 's law 

 thus simply expressed is only a close approximation to the 

 actual inheritance relations, and that the fraction indicating the 

 contribution of any given ancestor must be slightly modified 

 by introducing into it another factor. In general, though, 

 the . Galtonian formula received a very general acceptance 

 among biologists. And only recently, in the light of the discov- 

 ery of Mendel's investigations and conclusions and their confir- 

 mation in essential principle by the recent researclies of various 

 botanists and zoologists, has Galton 's law been looked on as 

 altogether too simple and incomplete a formulation of the facts 

 of inlieritance. It is not yet quite certain whether Galton 's 

 formula is consonant with the Mendelian formula or not. But 

 at best Galton's law only expresses a part of what may now witli 

 confidence be said to be known of the regular course of inher- 

 itance. 



Before taking up the actual Mendelian results and conclu- 

 sions, however, it is important for us to note the different modes 

 or kinds of behavior of inheritance which cliaracteristics may 

 show in their transmission. Cuenot has made a rough Init 



