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THE AMERICAN NATURALIST 



[Vol. XLV 



and the view is indirectly supported by the comparative 

 findings above described, viz.: (a) absence of connective 

 tissue cells (chromatophores) among the epidermal cells 

 (admitted by Karg for normal negro skin), (b) compara- 

 tive rarity of pigmented processes from cutis cells, and 

 (c) an apparently disproportionate number of chromato- 

 phores as compared with the epidermal pigment cells. 



(8) The agreement between the cytologic facts of 

 Meirowsky and the chemical results of Chittenden and 

 Albro, and others, that the antecedent of melanin is some 

 form of proteid. 



(9) The observations of Meirowsky showing a passage 

 of granules from the nucleus to the cytoplasm as the 

 initial step in melanogenesis, and a progressive colora- 

 tion of these granules to a final stage of yellowish-brown 

 pigment. 



(10) The production of artificial melanins ("mela- 

 noidins"— Schmiedeberg) by Chittenden and Albro and 

 others from ''antialbumid" and various proteids, and the 

 results described by Spiegler and Riddle and others indi- 

 cating an interaction of a chromogen (tyrosin compound) 

 with an oxidizing enzyme (tyrosinase) in the formation 

 of melanin. 



Discussion 



There appears, then, proximately to he only one factor 

 in skin-pigmentation, viz., the number of granules of 

 identical shade (yellowish-brown), incidentally the num- 

 ber of cells containing such granules. The granules 

 would seem to be the result of intracellular activities 

 (Meirowsky) and to have origin in cell proteids (Chit- 

 tenden and Albro, and Meirowsky). In terms of chro- 

 mogen and oxidase, the granules may be thought of as 

 tyrosin which under the influence of tyrosinase from the 



The n.Hanoovnotic process scorns to stop at the same 

 point in all grades of colored skin, from negro to blond- 

 in hair of the same it may possibly proceed slightly 

 further, though even this seems doubtful in view of ap- 

 pearances in the hair bulb. One seems to be dealing, then, 

 with a continuous process, i. e., the production of melanic 



