HEEEDITY 



The color variations of guinea-pigs are simi- 

 lar to those of mice; the same series of unit- 

 character changes has produced them with one 

 exception. The pink-eyed modification is want- 

 ing in guinea-pigs. We are therefore limited 

 here to the intense series, the pale series, the 

 intense spotted series, and the pale spotted 

 series. In each of these occur gray (or agouti) 

 individuals, black ones, cinnamon ones, and 

 brown ones. 



The parallelism between the color variations 

 in guinea-pigs and in mice received an inter- 

 esting demonstration in a particular case. The 

 brown pigmented series in mice has been 

 known for some time, but in guinea-pigs the 

 brown variety is of comparatively recent origin, 

 and the cinnamon variety was wholly unknown 

 until some three years ago. After an analysis 

 had been made in terms of unit-characters of 

 the color varieties of the mouse, it became clear 

 that if the color variation of guinea-pigs fol- 

 lowed a like course, a then unknown variety 

 of guinea-pig, cinnamon, should be capable of 

 production by crossing an agouti animal with 

 a brown one. In 1907 a statement of the sci- 



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