356 WILLIAM H. COLE 



control the process, and the mystery of the earher cases disap- 

 peared. Partial absorption of the graft, which occurred in so 

 manj'' cases, was undoubtedly caused by a mechanical stimulus, 

 probably a tension. 



During the study of the pseudoregulation which was observed 

 in transplants taken from the tail region onl}'^, the problem of a 

 possible local specificity of integument was presented. With this 

 problem in mind, the experiments were continued, using skin 

 from three different regions of the tadpole, namely, posterior 

 part of tail, the belly, and the back. The results obtained can be 

 interpreted only by assuming that in the integument of those 

 regions there are specific substances which retain their individu- 

 ality when transplanted to another region and which determine 

 the future history of the transplant. The grafts which were 

 taken from the belly region were white, due to the absence of 

 melanophores. After transplantation to the dark back region 

 such grafts acquire melanophores. An attempt was made to 

 discover the method of such acquisition. Autotransplants and 

 homoiotransplants of belly skin on the back region were studied, 

 and their behavior led to the conclusion that the source of the 

 graft determines the method of melanophore appearance. Ho- 

 moiotransplants are pigmented chiefly by migration of epidermal 

 melanophores from the surrounding skin. Autotransplants are 

 pigmented chiefly by formation of melanophores in situ. Finally, 

 the pigmentation of the conjunctiva, which may be produced 

 experimentally by an injury to that tissue, was investigated. 

 The description of such experiments will be found in the last 

 section of this paper. 



It is not the purpose here to review the extensive literature 

 on the transplantation of tissues and organs. Since the time of 

 John Hunter, about the middle of the eighteenth century, zoolo- 

 gists and medical men have transplanted all kinds of tissues and 

 organs under many different conditions and on different species 

 of animals. Korschelt ('07), Schone ('12), and especially Bar- 

 furth ('14) have arranged excellent bibliographies with discus- 

 sions of the important researches on this subject. For the ear- 

 liest works, the lists given by Bert ('66) and Reverdin ('92) are 



