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THE AMERICAN NATURALIST [Vol. XLV 



Cause of Degree of Coloration. — Theoretically at least 

 six possibilities are conceivable: (1) Number of pigmented 

 epidermal cells, or, indirectly, (2) number of pigmented 

 connective tissue cells of cutis, (3) number of pigment 

 granules in pigmented epidermal cell, (4) coloration of 

 granules in pigmented epidermal cells, (5) numbers 1 and 

 3, (6) combination of 1 or 3 and 4, or a combination of the 

 three. It is also theoretically possible that a difference in 

 the size of the granules may play a part in determining the 

 degree of coloration. In view of what was said under the 

 previous heading, number 2 can be disregarded and there 

 remain five plausible possibilities. Which " possibility " 

 or set of possibilities expresses the reality will become 

 clear from the description of the several types of skin. 

 In anticipation of ensuing results it may be said in brief 

 that there seems to be only one factor in skin coloration, 

 viz., the number of the pigment granules, a greater num- 

 ber of granules of course involving a greater number of 

 cells — with a small and possibly negligible variation in 



Description of Negro Skins 

 The several samples of skin will be described in the 

 order of their degree of coloration as seen from the sur- 

 face. This agrees almost absolutely with the degree (i. e. f 

 quantity) of the pigmentation factor, as will appear below. 



findings in lru.-„d,. r m;. ,|„ no! accord with thus.- of Dyson: (J) While it 

 may be true that the pigment granules of the cutis cells are slightly 



(2) In no case have /been able to discern melan.c granules in the nudei 



