122 BLASTOGENIC VARIATIONS. 



The variations of offspring are therefore largely pro- 

 duced by the mingling of dissimilar parental germ- 

 plasms, so that the offspring do not closely resemble 

 either each other or their parents. But there must 

 clearly be a relation of some sort between them. As 

 to the extent of this relation, we are chiefly indebted 

 for our knowledge to the labours of Mr. Francis Galton. 

 In his work on " Natural Inheritance/ 7 he has analysed 

 a very large number of anthropometric data which were 

 collected by himself specially for the purpose. The 

 most important of them consist of records of the 

 stature, eye-colour, artistic faculty, and condition of 

 health of the various members of some 150 distinct 

 families, extending over three or more generations. 

 Arguing from these data, he concluded that on an aver- 

 age each parent contributed to the characters of his or 

 her offspring J of their amount, or both parents to- 

 gether contributed a half; whilst each grandparent con- 

 tributed y 1 ^, or the four grandparents together J, and so 

 on; but he considered his data insufficient to warrant 

 him in extending the sequence to more distant genera- 

 tions. 



Some years later, Galton obtained other more fav- 

 ourable data.* These enabled him to ascertain the con- 

 tributions of ancestors to offspring with much greater 

 exactness, and warranted him in formulating a Law of 

 Ancestral Heredity, which there is some reason for 

 thinking may prove to be universally applicable to 

 bisexual descent. The data consisted in long series of 

 records of the colours of a large pedigree stock of 

 Basset hounds, extending through many successive 

 *Proc. Roy. Soc., vol. Ixi. p. 401, 1897. 



