No. 571] PATTERN DEVELOPMENT 



395 



the ear patch is missing, while those of the left side are 

 fully developed. In Fig. 4 both neck patches are missing, 

 so that a white collar is formed. In dogs the neck patch 

 is usually the first to drop out altogether, so that a white- 

 collared dog is of very frequent occurrence. In fox 

 hounds this patch is shown unusually well, either wholly 

 or partly separated from neighboring patches. The sep- 

 aration of the ear patches, wholly or partially, so as to 

 produce a white blaze or line in the middle of the forehead 

 is about as frequent. In Figs. 8 and 12 a single neck spot 

 only (as it happens, in one on the right, in the other on 

 the left side) is still present but so slightly developed as 

 to be only a small island of pigment wholly separate from 

 the neighboring patches. 



The crown spot is so often present in dogs as a little 

 oval island, always on the top of the head about in line 

 with the anterior bases of the ears (Fig. 4) that I am 

 convinced it is a primary patch. It is common in bull 

 dogs and bull terriers, and in other breeds is often seen 

 but is so commonly not indicated at all, that it seems 

 probable it is becoming lost, and its area is filled by the 

 ear patches, since these are often separated by a very 

 narrow median line only, which, as in Fig. 13, may con- 

 tinue posteriorly to separate the two neck patches 

 medially as well. In other cases (Figs. 1,6) the failure of 

 the white nose stripe to extend farther posteriorly may 

 be due to the persistence of this patch. 



The demarcation of the side from the rump patches is 

 indicated by the imperfect primary break across the 

 lower part of the back in Fig. 4, while in Fig. 5, a similar 

 primary break farther forward indicates the limits of the 

 shoulder and side patches. In each case the break is 

 incomplete transversely, with a narrow isthmus near the 

 median line. In dogs there is a marked tendency for the 

 ultimate centers of the side and rump patches to be close 

 to the median line, so that the corresponding patches of 

 opposite sides are confluent dorsally. This is espeeially 

 the case with the rump patches, with the result that it is 



