560 Allen, Pattern Development in Teal. [oct. 



tend to occur at the peripheries of the pigment centers as above 

 defined, and result from the failure of pigment to develop at the 

 edges of these centers. The more the pigmentation is restricted, 

 the greater is the amount of white between the respective centers. 

 If each patch or center were to be slightly reduced, a series of five 

 pigment spots on each side, and one on the crown would result, 

 bounded by white lines — a median white line from the occiput 

 to tail, and cross stripes separating the five patches of each side. 

 A much greater but regular restriction of each patch would result 

 in reducing the pattern to a series of five small spots on each side 

 with a single median one on the crown; and still further reduction 

 brings about a pure white condition with black eyes — (possibly 



Figure 1. — Diagram showing chief pigment areas of a bird's body, from 

 above. 



the eyes being in part of ectodermal origin, should themselves be 

 regarded as an additional pair of pigment centers). Such white 

 animals with black eyes occur as artificial breeds in a number of 

 species, and on account of their possessing a potential pigmenta- 

 tion, act as pigmented individuals in crosses with true albinos 

 which do really lack the pigment-producing factor. Actually 

 there is great variation in the amount of reduction, for not only 



