No. 572] PATTERN DEVELOPMENT 481 



break occurs between the neck patches and those of the 

 head as in Fig. 50. Posteriorly the neck patch under 

 reduction may become separated by a white ring at the 

 base of the neck, from the shoulder patches as iti Fig. 50. 

 The ultimate centers of these patches seem to be in the 

 pigeon well back on the base of the neck. These are 

 shown, of small extent, in Fig. 51, as two small areas of 

 pigmented feathers, one on each side of the base of the 

 neck. In Fig. 53, further reduction has taken place, so 

 that the patch of the left side only remains as a small 

 center. In Fig. 52 there is a large median dorsal patch, 

 which, as in mammals, may represent the two centers of 

 opposite sides which even under much reduction have not 

 in this individual become divided medially. 



A very common manifestation of pigment reduction in 

 pigeons is to have the primaries or some of them white, 

 as in Figs. 49 or 50. . This indicates a failure of pigment 

 to develop at the extremities of the shoulder patches, 

 just as in mammals white forefeet mark a slight reduc- 

 tion of the same areas. It is a fact of much interest that 

 in the guinea fowl (Numida), which has been under 

 domestication but a short time comparatively, a distinct 

 breed has arisen in which this same reduction of pigment 

 is present, resulting in a speckled bird with pure white 

 primaries and often a pure white area on the breast. In 

 the pigeon, further reduction cuts off a narrow ring of 

 pigment encircling the breast, or, it may be, broken in the 

 mid-ventral line. This ring represents the reduced 

 shoulder patches, and is to be seen in many wild species 

 as a permanent part of the pattern. The white collar at 

 the base of the neck in Fig. 50 marks the separation 

 between the neck and the shoulder patches at the ante- 

 rior border of the latter. In other specimens the patches 

 are separated medially by a white area down the back. 

 The ultimate centers of these patches seem to be near 

 the elbow or on the upper arm at the base of the tertiaries, 

 as seen in Figs. 52 and 53. 



