Manchester Memoirs, Vol. I. (1906), No. 11. 21 



stepped its limits when it included in such a table more 

 than one such category. What Bateson means when he 

 says that Mendel saw by sure penetration that masses 

 must be avoided is that the biometric method oversteps 

 its limits when it does this. 



The answer that I should now give to my friend is 

 this : ' I fully admit that the only method of measuring 

 the degree of resemblance between a generation and the 

 one which produced it, within such a unit, is the biometric 

 method : I fully agree with the biometrician, when he 

 says that all green peas are not alike in respect of their 

 greenness because all green peas are green, and that the 

 biometric method is the only one to measure their dis- 

 similarity ; but I stoutly maintain that when he puts 

 green and yellow peas together into a correlation table he 

 has started on a path which will not lead to a more inti- 

 mate knowledge of heredity.' 



Biometry furnishes the only means of actually 

 measuring the intensity of heredity within a unit : 

 Mendelism furnishes the only means by which a fuller 

 knowledge of the properties of these units may be 

 acquired.* 



It is sometimes easy to determine the extent of these 

 units as in the case of discontinuous characters such as 

 purpleness and whiteness of flower in Pisum : f it is often 

 difficult as in the case of characters varying continuously 

 such as the weight of beans.:|: 



Careful consideration of the table on p. 6 of my paper § 

 on the supposed antagonism of Mendelian to biometric 

 theories shews that the accuracy with which Mendelian 



* Exactly the same idea is expressed by Lotsy (:o6, p. 143). 

 + Fruwirth :06, p. 141. 

 X Johannsen :03. 

 § Darbishire :05«. 



