454 THE AMERICAN NATURALIST [Vol. XLV 



study of white skin transplanted to a negro and vice 

 versa, i. e., negro skin transplanted to a white individ- 

 ual; (2) that of Meirowsky (1908), who studied the origin 

 of melanic pigment in the skin and eye and, more espe- 

 cially, on the basis of experiments with pigeons and find- 

 ings in pigmented skin kept alive for several days in a 

 paraffin bath at a temperature of 56 degrees, urges the 

 first view. These two masterly papers advance dia- 

 metrically opposing views. Karg unqualifiedly put aside 

 the idea that pigment may be formed within the epi- 

 dermal cell. He says, "Es gelang so, festzustellen, das 

 es nur eines Modus der Entstehung des Pigments giebt. 

 Aus der Lederhaut dringen pigmentirte Zellen in die 

 Epidermis, verasteln sich hier weit und geben ihr Pig- 

 ment an die Epithelzellen ab," p. 370. Meirowsky de- 

 scribes conditions more in conformity with our later 

 ideas of cellular physiology. According to him, the 

 melanic granules are passed out of the nucleus of the 

 epidermal cell into its cytoplasm, i. e., pigmentation is 

 an intracellular process, both dermal and epidermal. 



Historically Riehl (1884) appears to have been the 

 first to describe the condition afterwards interpreted by 

 Karg as supporting his view of epithelial pigmentation, 

 viz., invasion of processes of pigmented connective tissue 

 cells among the epidermal cells. Riehl studied more 

 especially the pigment of hair. He did not generalize, 

 however; and while he thought it improbable, he did 

 not regard it impossible, that pigment may arise out of 

 the protoplasm of epithelial cells. He seems rather to 

 incline to the third view above stated. Moreover, on the 

 basis of findings in a study of three cases of Addison's 

 disease, where the adventitia of blood vessels was richly 

 infiltrated with pigmented cells coincidentally with a 

 hemorrhagic aggregation of red blood cells, he concludes 

 that the pigment arises from the haemoglobin of the red 

 cells. Aeby (1885) likewise describes the transporta- 

 tion of pigment to the epidermis by wandering cells. 

 Ehrmann (1885-86), who studied the pigmented epi- 

 thelium of amphibia, differs from Riehl and Aeby only 

 in holding that the pigmented stellate cells of the cutis 



