266 



The Journal of Heredity 



Just what this drag of the race means 

 to the breeder is expressed in mathe- 

 matical form by Galton's Law of 

 Ancestral Heredity, which is generally 

 found to be substantially correct where- 

 ever large numbers are concerned, 

 although it, like all other statistical 

 generalizations, may 

 leading in individual 

 Law states the average contribution of 

 each ancestor, all the way to infinity: 

 in the following table only the first six 

 generations are considered, the effective 

 heritage contributed by each of these 

 generations, and by each individual in 

 the generation, being expressed in 

 percents. : 



be wholly mis- 

 cases. Galton's 



of variation. So far as the opportunity 

 that variation always presents for 

 further selection is concerned, the 

 breeder will always have material avail- 

 able, but there are mechanical and 

 physiological limits beyond which no 

 amount of selection can ever be carried. 

 However, in all probability, these limits 

 have not been reached, except possibly 

 in the size of the very large and very 

 small breeds." 



(3) What are the principles involved 

 in rational selection? First and fore- 

 most, the breeder must know the points 

 of the dog he is breeding. He must 

 know the history of his breed. A 

 knowledge of the famous dogs of the 



In other words, the individual gets 

 only half his heritage from his parents, 

 the rest from his more remote ancestors. 

 The true object of selection, therefore, 

 is to establish a strain in which the 

 ancestors as far back as possible will 

 conform to the desired type. 



(2) Can selection accompUsh this 

 object ? Theoretically yes, without any 

 hesitation. "A somewhat involved 

 mathematical proof has been worked 

 out to show that after six generations of 

 careful and continued selection a certain 

 character will invariably breed true. 

 No further selection for that point is 

 necessary, provided no dogs which will 

 deteriorate the inheritance for that 

 point are introduced into the strain." 

 A good ]3edigree for six generations is 

 for most jjurposes as good as one for 

 sixty. 



"The breeder can cxj^ect that intel- 

 ligent, continued selection will change 

 type in any desired direction, and that 

 new tyjjc will breed true after six 

 generations of continued selection. He 

 cannot, however, expect to accomplish 

 any material reduction in the amount 



past will soon serve to locate prepotent 

 strains, which have perhaps been pro- 

 duced by inbreeding, and which can be 

 of great value. Study of pedigrees, 

 then, is a matter of vital importance; 

 and as a practical rule, the breeder 

 must set before him an ideal and always 

 breed toward it. 



So much for the principles of dog 

 breeding. In the second part of the 

 book Mr. Haynes discusses practice 

 rather than theory. What he says 

 about inbreeding will be particularly 

 interesting: 



WH.\T INBREEDING MEANS. 



"The whole subject has been badly 

 muddled by a loose use of the term 

 inbreeding, and by very hazy notions 

 on the ])art of every one concerned as to 

 just how common true inbreeding is 

 among dogs. 



" Inbreeding means nothing more nor 

 less than the crossing of the blood of 

 one individual. There are only three 

 possible ways in which this can be 

 accomijlished. (1) By breeding a sire 

 to his own daughter. (2) By breeding 



