An Introduction to a Biology 



werden." 1 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 him- 

 self tentatively suggested, 2 when he formulated his Law, 

 that it might become applicable to the individual. 3 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 statis- 

 tical 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 in- 

 sensate 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 proclaims that his results prove 

 that ancestry makes a difference, without making it clear 

 whether he has in mind a physiological or a statistical theory, 

 is drawing a conclusion which is meaningless. For his con- 

 clusion to have a meaning, he must make this clear. If he 

 is referring to the former, he is declaring for the Law of 

 Contribution ; if to the latter, for the Law of Ancestral 

 Inheritance. 



When the Mendelian says that ancestry does not make 



1 Lotsy, :06, p. 152. * See Appendix A, p. 196 infra. 3 Galton, '97, p. 403. 



190 



