THE 



AMERICAN NATURALIST 



Vol. LIV. November-December, 1920 No. 



TYPES OF WHITE SPOTTING IN MICE 1 

 L. C. DUNN 



Storrs Agricultural Experiment Station, Storrs, Conn. 

 The occurrence of white spotting in the coats of col- 

 ored mammals is one of the commonest phenomena en- 

 countered by the student of variation and heredity. For 

 a long time spotting was thought to be of the same nature 

 as albinism, a condition in which no pigment is present in 

 the fur and eyes, leaving the pelage clear white and the 

 eyes pink. Many specimens of white spotted animals 

 are still to be seen in museums masquerading as ''partial 

 albinos. " 



As soon as the methods of experimental breeding were 

 employed in studying such variations, albinism and white 

 spotting were found to be genetically distinct. Albinism, 

 because of the striking nature of the variation and its 

 almost identical appearance wherever encountered was 

 one of the first mammalian variations to lie analyzed and 

 its mode of inheritance is now well known. The case of 

 white spotting is quite different. The spotting of most 

 animals presents an extremely wide range of variation. 

 An almost continuous series may be traced by the casual 

 observer from the extreme spotting of white dogs with 

 black eyes to the small star or blaze on the foreheads of 

 some colored horses. The solid colored condition, gen- 

 erally known as self, and spotting may thus in some in- 

 stances be distinguished only by the presence of a few 

 white hairs. Moreover, the inheritance of white spot- 

 ting in different animals and of the various grades of 



i The experiments reported in this paper were performed at the Bussey 

 Institution, Harvard University, Forest Hills, Mass. 



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