FUR ANIMALS 



1393 



indicates that two different genes are involved in Alaskan and standard 

 black foxes. 



In some instances when Alaskan blacks and standard blacks were 

 mated, black young occurred in the litters. Check ma tings demon- 

 strated that the occurrence of black in the first filial generation was 

 due to the fact that one or the other of the parents was not pure but 

 hybrid for either A or B. 



Inadequate facilities and lack of funds made it impossible to main- 

 tain a sufficient number of foxes at the Fur Animal Station to make a 

 complete investigation of this kind. Therefore, the research workers 

 had to solicit the cooperation of fox farmers who had been conducting 

 cross-breeding experiments in the United States and Canada. They 

 willingly furnished the data obtained from their breeding operations, 

 and these proved to be most valuable in amplifying the results ob- 

 tained at the experiment station. 



Hanson made a biometrical analysis of these data and found that 

 three principal colors in foxes are inherited in accordance with the 

 factor hypothesis previously mentioned. In 775 Utters, including 

 over 3,000 pups, representing 30 different combinations of types, 

 only 4 litters were reported in which the results were contrary to the 

 hypothesis. In at least two of these cases there was some doubt as 

 to whether the vixen was served by two different males or whether 

 the parents were improperly classified as to color. 



Hanson designed a chart to illustrate the results of the various 

 matings on the basis of two-factor inheritance (fig. 6). At the top of 

 this chart is a key to the three different colorings and the nine different 

 combinations of genes that result in nine different types. Directly 

 under the key is a series of smaller nine-block squares giving the 45 

 different mating combinations of these nine types. The black squares 

 in the blocks represent the genetic types mated and the numerals 

 represent the expected distribution of progeny in proportions. Refer- 

 ence should be made to the key at the top of the chart to determine 

 the colors (fig. 7) and genetic make-up of the animals being mated 

 and also the progeny. 2 



As examples of the use of the chart: Suppose Alaskan blacks are to 

 be mated with standard blacks. This mating is given in the set of 



2 In matings producing more than one kind of progeny the result may deviate in the distribution of progeny 

 in individual litters or in a small number of litters, not only among foxes but among other animals also. 

 For example, the expectation from crossing a substandard black with an Alaskan black (fig. 6, square 32) 

 is that the progeny will consist of blended crosses and sub-Alaskan blacks in a 1:1 (50:50) ratio. As likely 

 as not, this mating will produce an equal number of crosses and blacks (silvers). The probable occurrence 

 of different combinations of cross and black foxes in Utters of four thus produced is as follows: 



Black (silver) foxes 4-3-2-1-0 



Cross foxes -- 0-1-2-3-4 



Total 1111 -4 



Although these figures represent the proportion of black (silver) and cross foxes that may occur in litters 

 of four, fitters of that size do not always occur. In sufficient numbers there would be produced six times 

 as many litters containing equal numbers of silver and cross foxes as there would be litters of all silvers or all 

 crosses. Likewise the litters with three pups of one color and one of the other would be produced four 

 times as frequently as would be litters of all one color. 



Figure 7. — Fox pelts of the nine genetic types, upper and under side illustrated in 

 each case, and grouped as in the square diagram in figure 6: A, Red, A ABB; B, 

 smoky red, AABb; C, standard black, A Abb; D, Alaskan red cross fox, AaBB; E, 

 blended cross fox, AaBb; F, substandard black, Aabb; G, Alaskan black, aaBB; 

 H, sub-Alaskan black, aaBb; i, double black, aabb. 



