26 DarbisHIRE, Lazvs of Hereaity. 



Merkmale ausgeschlossen werden."* Here " Galtons 

 Theorie " is made to refer not merely to the individual 

 but to the gamete borne by it, and the expression as here 

 used means nothing more nor less than the Law of 

 Contribution. It is true that Galton himself tenta- 

 tively suggested,! when he formulated his Law, that it 

 might become applicable to the individual. :J: But his 

 Law as it stands is a statistical Law true of masses of 

 units ; and when a physiological theory of heredity, as in 

 the above quotation, is spoken of as " Galtons Theorie" it 

 is high time that a new term is invented to describe it : I 

 have proposed the " Law of Contribution." 



Nothing could be more fatal to profitableness of dis- 

 cussion than that two such profoundly different things as 

 Galton'.s Law and the Law of Contribution should go by 

 the same name. 



So long as physiological are not clearly distinguished 

 from statistical Laws of heredity, biologists will continue 

 to slide from meaning a physiological to meaning a 

 statistical one : and the transition will be unconscious 

 because the term by which they denote these two different 

 things is the same — namely Galton's Law. Progress in 

 the study of heredity will be slow as long as this confusion 

 prevails. For so long as it prevails we shall continue 

 to hear the insensate statement that ancestry makes a 

 difference. Of course it makes a difference — in the mass; 

 which it is the business of the biometrician to measure 

 and of the Mendelian to account for. Anyone who pro- 

 claims that his results prove that ancestry njakes a 

 difference, without making it clear whether he has in mind 

 a physiological or a statistical theory, is drawing a con- 

 clusion which is meaningless. For his conclusion to have 



* Lotsy :o6, p. 152. 

 t See Appendix A. 

 :|; Galton '97, p. 403. 



