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THE AMERICAN NATURALIST [Vol.XLVI[I 



The approximate boundaries of the five bilateral patches 

 are indicated in Fig. 20 by dotted lines ; 2 is the ear patch, 

 3 the neck patch, 4 the shoulder patch, 5 the side patch, 

 and 6 the rump patch. 



Among domesticated rodents the pigment patches have 

 been studied in rats, house mice, and guinea-pigs. In 

 all, the same patches appear except that in rats and mice 

 the median crown patch appears to be lost, though in the 

 guinea-pig it is often present. Diagrams of parti-colored 

 mice are shown in Figs. 21-24, and sufficiently indicate 



the primary pigment areas. The white spot on the fore- 

 head of Fig. 21 indicates a primary break between the 

 two ear patches, and varies widely in different individ- 

 uals, from a few white hairs only to a large blaze The 

 inheritance of such a blaze has been studied by Little 

 (1914). The white mark at the base of the neck in Fig. 

 21 indicates the beginning of separation of the neck from 

 the shoulder patches and perhaps of the two neck patches 

 from each other, because of its longitudinal extension. 

 The white band across the neck in Fig. 23, however, 

 indicates probably only the beginning of a separation of 

 the neck from the shoulder patches, which in Fig. 24 has 



