No. 571] PATTERN DEVELOPMENT 391 



between two adjacent patches is merely indicated by a 

 white streak to that in which it is reduced to a small spot 

 of pigment, or to zero, when the entire patch drops out, 

 leaving a white area. These patches are wholly independ- 

 ent of each other in the extent to which they may be 

 developed, so that a particular patch may be quite want- 

 ing on one side of the body, while its fellow of the oppo- 

 site side is completely developed. Nevertheless, there is 

 often a marked tendency to bilateral symmetry in such 

 reduction. From a study of partial albinos in which the 

 pigment reduction is considerable, the location of the 

 ultimate centers of these patches becomes possible as well 

 as the determination of their normal extent, I have 

 studied several domesticated species in which white 

 marks are common, with the results briefly detailed below. 



When all the centers are- fully developed the animal is 

 completely pigmented; when none is developed, it is a 

 total albino. Between these extremes may lie found every 

 conceivable degree of development. In an ideal case in 

 which each center is slightly reduced so as to be circum- 

 scribed by white, the animal would have a dark coronal 

 or crown patch and a series of five patches on each side 

 separated by a median dorsal and a median ventral 

 stripe. The anteriormost of the lateral patches center at 

 the base of each ear, and each in its greatest development 

 covers the side of the head from muzzle to behind the 

 ear. These I have called the aural or ear patches; the 

 next posterior are the two neck or nuchal patches each 

 of which pigments its proper side of the neck, and extends 

 from behind the ear to the shoulder and anterior edge of 

 the foreleg. When much reduced the patch, as it were, 

 contracts to a small area on each side of the neck, varying 

 slightl v in its location among different species. Posterior 

 to these come the scapular or shoulder patches one on 



and foreleg, except (usually) the front edge of the upper 

 part of that member. This patch shows interesting^slight 



