X 0l ' i9f(? VI1 ] Allen, Pattern Development in Teal 559 



of the body may be divided into some eleven areas from whose 

 individual centers the tendency to produce pigment in the epi- 

 dermal structures (hair or feathers) tends to become less and less 

 as the periphery of the particular area is reached. These areas 

 may bear some as yet unrecognized relation to the distribution 

 of nerves. The borders of contiguous areas may overlap, and 

 the details of their topography in different mammals and birds may 

 vary, but in general their outlines are fairly definable as follows: 



(1) a median crown patch, in birds pigmenting the top of the 

 head from base of beak to occiput above the eyes; (2) an ear 

 patch on each side covering the side of the head and upper throat 

 from the level of the eye to the median line above and below; 

 (3) a neck patch on each side pigmenting the area from the upper 

 throat to the shoulders ; (4) a shoulder patch on each side pigment- 

 ing the feathers of the wing and a narrow area at its base from 

 center of back to center of breast; (5) a side patch on each side of 

 the body which includes the area from shoulder to rump; and (6) 

 a rump patch on each side which pigments the posterior end of 

 the body, the tail, and most or all of the hind leg. These patches 

 are outlined in the accompanying diagram (Fig. 1). I have 

 called these color areas primary patches. They may break up 

 further to form complex patterns. 



The definition of these patches is sometimes complicated by two 

 (or three?) other types of pigmentation which in some species 

 co-exist with this centripetal type — namely, a diffuse pigmentation 

 from many small independent centers, producing the spotted 

 effect seen for example in the Dalmatian Coach Dog, and a cen- 

 trifugal type, which produces black "points" at tips of nose, ears, 

 limbs or tail in certain species. A black median area on the 

 spine is perhaps a manifestation of this same type. These three 

 types of pigmentation behave differently in heredity and have been 

 studied lately by several geneticists. It is likely that the median 

 crown patch, very small in mammals, may really consist of two 

 bilateral centers, here in close juxtaposition for in birds it is fre- 

 quently divided by a white median line, though in the few mammals 

 where I have seen it (e. g., dogs) it is not so divided. 



From a study of pied individuals of species which normally 

 have complete pigmentation, it is found that the white markings 



