Manchester Memoirs, Vol. I. (1906), No. II. 23 



The point that I wish to bring home to the reader is 

 that the statement that Mendelism deals with units, and 

 biometry with masses, is not merely a brief summarising 

 statement which pleases the mind, but that it has an 

 actual meaning in relation to the facts : that is to say, 

 that the limits of these units are not set by the imagina- 

 tion, but are discovered by experiment. 



4 (f). Examples of the confusion between physiological 

 and statistical Laws. 



Having spoken this much on the difference between 

 physiological and statistical Laws of heredity I propose to 

 consider a few cases where failure to perceive this difference 

 has led to confusion. As I have already referred to 

 Castle's case I will finish with it before I proceed to others: 

 he says* " The foregoing results show very clearly that 

 albinism conforms in the mode of its inheritance to 

 Mendel's law of heredity. The fact, however, must not 

 be overlooked that a somewhat different explanation of 

 its inheritance^ has recently been given, based on Galton's 

 "law of ancestral heredity." I shall not at this time 

 enter into a detailed discussion of Galton's hypothesis, 

 which was an entirely rational one in the form in zviiich it 

 was originally proposed'^ and quite in harmony with the 

 phenomena oi ga?netogenesis^ as then interpreted. I have 

 showrx elsewheref by a specific test in the case of mice, 

 based on the observations of von Guaita, that Galton's 

 law fails to account for the observed facts^ concerning the 

 inheritance of albinism, but that Mendel's law does this 

 perfectly. Nevertheless Darbishire, likewise dealing with 

 albinism in mice, though admitting that certain of his 

 results are not in disagreement with Mendel's law, is 



* Castle :05, p. 16. t Castle, -.03, p. 231. 



