INHERITANCE OF WHITE-SPOTTING IN RABBITS. 7 



produced only one type of Dutch young varying around grade IG. 

 (See table 19.) 



By studying the results of various matings of our Dutch does it 

 was found possible to classify them in three categories: (1) The 

 ^'white" type of grade 15 to 17, which produced only the "white" 

 type when mated with bucks of the same sort, as already described. 

 (See plate 2, fig. 19.) (2) A "dark" type of grade 1 to 7, which when 

 mated with bucks of the white type produced no "white" offspring, 

 but only those of the dark type. These mothers were evidently homozy- 

 gous "dark,'' the other pure type (see plate 2, fig. 20). (3) The third 

 type of doe is scarcely distinguishable from the pure dark type except 

 by breeding test. It consists of heterozygotes between the two types, 

 a little whiter on the average than the dark type, but not conspicu- 

 ously so. When they are mated with "white" bucks, young of two 

 types are produced in about equal numbers, viz, heterozygous darks 

 and pure whites. The original Dutch bucks from which the entire race 

 was derived were both of this heterozygous dark type. 



Neither the dark type nor the white type isolated from this race of 

 rabbits conforms closely with the ideal Dutch type of the fancier (our 

 grade 8). The one is usually too dark and the other too white. It 

 seems probable that the fanciers in breeding "prize-winners" have 

 consciously or unconsciously been producing heterozygotes, very much 

 as in the case of the Andalusian fowl. Certain it is that all the rabbits 

 which we have produced from this stock, which would have any 

 chance of winning a prize at an exhibition, have been heterozygotes 

 between these two types. 



While the experiments with standard-bred fanciers' Dutch rabbits 

 were in progress, and after the white and the dark types of Dutch had 

 been isolated, a third type of Dutch was discovered which kept crop- 

 ping out in a stock of black-and-tan rabbits under observation for 

 another purpose. This stock was derived from a single pure-bred 

 black-and-tan buck which had been crossed with various other stocks 

 of rabbits then in the laboratory. The Dutch pattern had been 

 introduced as a recessive character in a certain j^ellow rabbit of 

 unknown pedigree obtained by purchase. When the descendants of 

 this yellow rabbit were bred with each other, certain of the young 

 produced were Dutch marked. This type of Dutch resembled the 

 fanciers' type of Dutch (grade 8, plate 1) so far as the head markings 

 were concerned, but the belt was very narrow and placed far forward 

 over the shoulders. (See plate 2, fig. 21.) Because of its origin within 

 the black-and-tan stock we have adopted the name "tan" Dutch to 

 distinguish it from the other two types. 



In describing its variations we have used the same set of grades 

 (shown in plate 1) which were used in classifying the variations of 

 the other two types, but it must be understood that rabbits of the 



