126 Basset Houiids [ch. 



^^ Tricolour^^ and ''Non-tricolour'' in Basset Hounds: 

 The Law of Ancestral Heredity. 



The question of the relation of the yellow and black 

 pigments is raised in the celebrated case of the colours of 

 Basset Hounds. The importance of that subject is due to 

 the fact that it was from a study of the evidence in regard 

 to Bassets that Mr F, Galton was led to enunciate his 

 *'Law of Ancestral Heredity" with confidence as one which 

 "appears to be universally applicable to bi-sexual descent." 

 The publication of that paper played a considerable part in 

 the history of modern genetic research and it is necessary 

 that we should consider the facts in some detail. 



The colours of Bassets are two, the first spoken of as 

 tricolour, consisting of black and yellow marks on a white 

 ground ; the second, non-tricolour, which differs from the 

 first in having no black. It is said that dogs which cannot 

 be easily referred to one or other of these two types do not 

 occur, and they must certainly be very rare if they exist at all. 



Mr Galton s investigation was based on data supplied to 

 him by the late Sir Everett Millais, a keen fancier of the 

 breed. This evidence consisted in records giving the 

 number of offspring of each type which had occurred in 

 families of various compositions. It was thus possible to 

 compare the number of tricolour and non-tricolour dogs 

 produced in the families with the number of the respective 

 types distributed among their pedigrees. Galton's figures 

 indicated that there was a close correspondence between 

 these two numbers, so that it was possible, given the 

 ancestral composition of the families, to predict with con- 

 siderable accuracy the numerical proportions in which the 

 respective types would appear. According to Galton's system 

 the family was regarded as the production of all the ancestors. 

 Each ancestor was supposed to contribute in his or her 

 degree to this total heritage, the more immediate progenitors 

 contributing more, and the remoterprogenitors less, according 

 to a definite arithmetical rule. This rule was that the average 

 contribution of each ancestor was to be reckoned 



for each parent 1/4 



for each grandparent 1/16 



for each great-grandparent 1/64 



