312 



The Journal of Heredity 



faded yellow in color does not appear 

 to have been considered. From analogy 

 with all the forms previously worked 

 on, in which a dilution factor of the 

 type apparently existing in cocker 

 spaniels has been established, one would 

 expect that such would be the . case. 

 What we believe to be conclusive 

 evidence of a dilution factor in Great 

 Danes will be considered later. 



The evidence on the inheritance of 

 spotting obtained by Barrows and 

 Phillips is extremely interesting, for it 

 apparently demonstrates that there are 

 at least two types of spotting. Thus 

 spotted by spotted matings produced 

 two hundred and twenty spotted and 

 fourteen solid colored individuals. The 

 spotted parents in these cases were 

 apparently the ordinary parti-colored 

 cockers in which considerable white is 

 always present. When solid pigmented 

 anim.als were crossed together, nineteen 

 solid colored individuals were produced, 

 and in addition two pups from a single 

 litter showed very small white spots on 

 the breasts. We shall see later that 

 these conditions are paralleled closely 

 in Great Danes. 



Wright, 1918, in reviewing color 

 inheritance in mammals, recognizes in 

 dogs the existence of the B and E factors 

 and of the dominant spotting which he 

 calls R, or roan. Just how far this roan 

 factor is similar to the fine mixtures of 

 pigment found in the roans of horses 

 and cattle is uncertain. It seems quite 

 possible that in short-haired dogs such 

 as Great Danes or coach-dogs, a type 

 of color distribution which in the long- 

 haired breeds such as English setters 

 produces a mixture of indistinct spots 

 and regions of apparent "roaning," 

 might produce clear, well-defined spots. 

 The possible danger of considering the 

 dominant spotting found in cocker 

 spaniels a true roan is seen in such 

 varieties of dogs as the "tigered" or 

 "dappled" dachsund. Here there ap- 

 pears to be a real intermixture of black, 

 sparsely pigmented, and almost, if not 

 entirely unpigmented hairs; a condition 

 which more closely resembles the roans 

 which have hitherto been described. 

 Wright further recognizes a probable 



factor for piebald spotting which he 

 considers at the present time un- 

 analyzed. He also mentions the inter- 

 esting experiments of Pearson, Nettle- 

 ship, and Usher, resulting in the isola- 

 tion of a factor for partial albinism in 

 Pekinese. With this brief review we 

 may now turn to a consideration of the 

 observed facts. 



II. OBSERVED EXPERIMENTAL RESULTS 



The following matings have been 

 recorded from data derived from the 

 American Kennel Club Stud Books, 

 Volumes 11 to 34 inclusive. As was 

 the case in pointers, numbers before 

 Volume 11 represented data collected 

 at a time and under circumstances not 

 well adapted to accuracy, and con- 

 tained only a small number of available 

 animals. The strong and weak points 

 in data collected from stud books have 

 already been touched upon in an earlier 

 paper by one of us already referred to 

 (Little, 1914), and need not be further 

 considered at present. 



Inasmuch as many types of matings 

 have been involved, it will be convenient 

 to analyze them in groups according to 

 the particular factor or factors which we 

 believe they possess. 



III. THEORETICAL INTERPRETATION 



A breed of dogs such as Great Danes 

 may biologically be considered as a 

 mixed population. In so far as any 

 one pair of allelomorphs are concerned 

 there will be individuals of three sorts: 

 DD, DR, and RR. If there has been 

 no particular degree of inbreeding or 

 selection, they will probably be present 

 in approximately the proportion of one 

 DD, to two DR, to one RR. Con- 

 sidering for a moment only the D in- 

 dividuals we find that in proportion to 

 the degree of inbreeding and selection, 

 the relative number of DD individuals 

 becomes greater, and we might therefore 

 expect some populations to show among 

 their D animals a ratio of one DD to 

 one DR, or perhaps two DD to one DR. 



For a population in which DD and 

 DR animals are present in these different 

 proportions, characteristic ratios of D 

 to R individuals will be formed as the 



