398 WILLIAM H. COLE 



of the dermis was observed. But in none of the sections was there 

 conclusive evidence as to the origin of the melanophores. Be- 

 fore proceeding to a discussion of these results and a possible 

 explanation of them, a brief review of some work done on other 

 animals will be given. 



Carnot et Deflandre ('96) grafted small pieces of black skin 

 into unpigmented regions of guinea-pigs, and observed the spread- 

 ing of pigment from such grafts into the surrounding white skin. 

 The process was slow, requiring weeks before the pigment became 

 noticeable. They further found that the rate of extension of the 

 pigment varied according to whether the host was an albino or a 

 dark colored animal. In the latter case, the rate was described 

 as 'rapid,' while in the former it was extremely slow. This result 

 indicated to them that the extension of pigment was not de- 

 pendent upon the grafted cells alone, but upon the available 

 supply of melaniferous substances in the host as well. Their 

 account implies that pigment is formed in situ as the result of 

 some stimulus from the graft's acting upon the neighboring skin. 



In the following year Loeb ('97) reported that when pieces of 

 black skin from guinea-pigs' ears are grafted to a white region 

 denuded of skin, the pigment spreads out from the graft into the 

 white skin; also that when the reciprocal graft was made, the 

 white skin became pigmented, the process beginning at the 

 edges of the graft and proceeding to the center. From these and 

 later experiments (Loeb and Strong, '04), he concludes that the 

 epidermal melanophores arise from ordinary epidermal cells which 

 have become filled by pigment and become branched, and that 

 they are also capable of rapid migration. Winkler ('10) found 

 that the white skin of frogs or tadpoles transplanted to a black 

 region became black. He believed that the pigment is formed 

 in situ, and that the formation of pigment is an inherent function 

 of the epidermis. 



In order to discover any variations in the process that might 

 be found in autotransplants and homoiotransplants, the experi- 

 ments of Loeb were repeated by Sale and Seehg. They both 

 used guinea-pigs. Sale ('13) found that an autotransplant of 

 black skin on a white region extends its pigment into the sur- 



