4 Darbishire, Laivs of Heredity. 



a capital L because that is the conventional way of 

 writing terms the discussion of whose meaning is post- 

 poned. 



2 (a). Pearson^ s Law. 



No one has any excuse for not knowing what the 

 Law of Ancestral Inheritance is ; the essential features of 

 it are outlined by Pearson in the following words : — 



" Taking our stand then on the observed fact that a 

 knowledge neither of parents nor of the whole ancestry 

 will enable us to predict with certainty in a variety of 

 important cases the character of the individual offspring 

 we ask : What is the correct method of dealing with 

 the problem of heredity in such cases ? The causes 

 A, B, C, D, E, ... which we have as yet succeeded in 

 isolating and defining are not always followed by the 

 effect X, but by any one of the effects U, V, IV, X, Y. 

 We are, therefore, not dealing with causation but corre- 

 lation, and there is therefore only one method of procedure 

 possible ; we must collect statistics of the frequency 

 with which U, V, W, X, Y, Z respectively follow on 

 A, B, C, D, E .... From these statistics we know the 

 most probable result of the causes A, B, C, D, E and the 

 frequency of each deviation from this most probable 

 result. The recognition that in the existing state of our 

 knowledge the true method of approaching the problem 

 of heredity is from the statistical side, and that the most 

 that we can hope at present to do is to give the probable 

 character of the offspring of a given ancestry, is one of 

 the great services of Francis Galton to biometry.* 



2 {b). Galton's Law. 

 Galton formulated his Law as follows : " The two 



• Pearson, :03a, p. 215. 



