THE GENETIC BEHAVIOR OF MICE OF THE 

 COLOR VARIETIES "BLACK-AND-TAN" 

 AND "RED" 



L. C. DUNN 



Eaely in 1914 there were received at the Bussey Insti- 

 tution certain stocks of mice obtained from fanciers in 

 England. Some preliminary studies of the mice were 

 made by Professor Castle and Dr. Little. A more inten- 

 sive study of one race, the black-eyed-white, was after- 

 ward made by Dr. Little and independently by Dr. Detlef- 

 sen. The remaining stocks were turned over to Mr. W. F. 

 Whittier, who carried on experiments with them partly 

 at the Bussey Institution, partly at the Massachusetts 

 Agricultural College, recording some 2,500 offspring. 

 After devising the color grading scale and the general 

 methods followed in the later experiments, he relinquished 

 the work to the present writer. Since that time about 

 2,000 young have been recorded, bringing the total to 

 4,500. All the work has been done under the advice and 

 direction of Professor Castle. 



The principal varieties which have been used in these 

 experiments are known in England as "black-and-tans" 

 and "reds." The genetic character of these mice was at 

 the outset quite unknown, and in this paper it is proposed 

 to give some account of their genetic behavior, and since 

 they have proved to be forms of yellow mice, to assign to 

 them and their derivatives places in a scheme of classifica- 

 tion of the yellow varieties. 



The black-and-tan race has presented throughout the 

 more interesting problem. In appearance these mice are 

 of an intense shiny black dorsally, with a belly super- 

 ficially dear yellow. The belly hairs, however, are marked 

 by having dull black bases, hidden by the longer and over- 

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