SHANK COLORS IN DOMESTIC FOWL. 245 



the corium the latter cells lie in an almost unbroken mass. 

 Whenever either kind of pigment was found in the epidermis 

 the corium was also found to be supplied, but there appeared to 

 be no agreement between the quantities in the two layers. The 

 thickness of scales when granules lie in them is of importance 

 in regulating intensity of color. Naturally those scales which 

 are the thickest, everything else being equal, are the darkest. 



Lipochrome pigment may be diffused through the epidermis. 

 Where much melanin pigment is present in the epidermis the 

 yellow color of the oil has no eft'ect upon the resultant color, but 

 when the epidermis is sparsely supplied with melanin pigment 

 the black color is modified. This condition will be considered 

 later. 



It should be particularly noted that a dense black shank color 

 may be associated with any other underlying dermal or epi- 

 dermal color. Thus one gets, in different cross-bred birds, as 

 I am informed by Dr. Raymond Pearl, dense black over white, 

 over yellow, over blue, and over green. 



Green.- — -This colored shank is characterized by the presence 

 of lipochrome pigment in the epidermis, and numerous melanin 

 pigment cells in the upper corium. It is an optical color result- 

 ing from melanin pigment lying under the semi-transparent 

 yellow epidermis. There is no melanin pigment in the epider- 

 mis. 



Black over green. — This shank color is similar to that de- 

 scribed immediately above with the addition of masses of 

 melanin pigment in the epidermis. In the black portions the 

 melanin pigment occurs as granules in both layers, and often in 

 addition as pigment cells in the Malphigian layer. These black 

 spots seldom cover more than a single scale, and usually are 

 much smaller. 



Black over white (dusky white). In this case a thin sprink- 

 ling of melanin granules occurs in the epidermal layers, and 

 frequently in addition scattered melanin pigment cells in the 

 Malphigian layer. There are usually melanin pigment cells in 

 the corium but not in sufficient quantity to deepen the shade, 

 else the skin would appear black. There is no lipochrome pig- 

 ment in either layer. 



