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THE AMERICAN NATURALIST [Vol. XLVIII 



domestic dog, all of which are carefully drawn from 

 photographs or from living animals, and are selected 

 from a great number to show various conditions in the 

 reduction of the pigment patches. In these and the other 

 diagrams the black portions represent pigmented areas, 

 irrespective of the actual colors. 



For convenience I have called the white stripes demark- 

 ing these chief or primary- patches, "primary breaks," 

 since they are the first indications of a decrease in pig- 

 mentation such that two adjoining patches no longer 

 meet. Secondary or further breaks result in a general 

 disintegration of these primary pigment patches, and are 

 apparently more irregular in nature, though often they 

 follow certain fairly well defined lines. The first of the 

 primary breaks generally occur as white patches on the 

 chest or belly, about in the median line. These are not 

 shown in the dagrams, but in most cases should be under- 

 stood as present. In Fig. 1 the pigment areas show a 

 beginning in reduction. The two aural patches have 

 become separated and their failure to spread to the 

 normal limit in the median line has resulted in a white 

 nose stripe. A short transverse white marking indicates 

 a separation of the neck patch at its anterior edge from 

 the ear patch. Elsewhere the various patches are contig- 

 uous; but the extremities of the limbs and tail are pig- 

 mentless, as if pigment had failed to spread to the tips of 

 these members in its reduction. In Fig. 2 the same 

 primary break between the ear patches is present, and in 

 dogs it is one of the first and most frequent to appear. 

 The same shrinkage of pigment from the extremities is 

 also seen. The neck patch of the left-hand side, however, 

 has completely dropped out, and its fellow of the right- 

 hand side is reduced posteriorly so that it fails to reach 

 the shoulder patch. Tims a white collar is formed. It 

 is also interesting to see that at its anterior end a distinct 

 constriction is present where the neck patch joins the ear 

 patch of the right side. Fig. 3 shows a somewhat similar 

 condition but the neck patch of the right side as well as 



