SKIN TRANSPLANTATION IN FROG TADPOLES 391 



congestion, the graft remained unchanged for two or three days. 

 The second feature of the grafts was a lymphocytic reaction 

 similar to that described by Loeb ('20). It was seen in sections 

 that nearly all of the available spaces between the dermis and the 

 epidermis were filled by lymphocytes. Several weeks after this 

 condition appeared, the fibrous layer of the dermis showed evi- 

 dence of disintegration and replacement by new tissue. The 

 more less continuous sheet of dermal melanophores found in 

 normal back skin was broken up into isolated irregular pigment 

 masses. The epidermal melanophores had greatly increased in 

 number and melanin granules were frequently abundant through- 

 out the epidermis. Macroscopically, the graft was considerably 

 Ughter in color than the surrounding skin, due to the condition 

 of the dermal pigment cells. Sections of grafts from the venter 

 also showed the degeneration of the dermal layer. The lympho- 

 cytes were very numerous and the epidermis contained many 

 melanophores, and scattered melanin granules. Dermal melano- 

 phores, of course, were absent. The acquisition of black pigment 

 cells by white belly-skin grafts is the subject of the following 

 section of this paper and will be described there. 



The congestion and lymphocytic reaction are interpreted as the 

 first steps in a process of replacement of the graft by new tissue 

 formed by the host. The occurrence of such a process is evidence 

 of a rather violent chemical reaction going on between the pro- 

 toplasms of the graft and host, and a merely specific difference 

 between the two could set up the reaction. This condition con- 

 firms the observation of many others that the protoplasm of one 

 individual is chemically different from that of a second individual 

 of the same species. Winkler ('10) made reciprocal homoio- 

 transplants of back and belly skin in Hyla, and found that they 

 retain their individual characteristics. In 1913 Borst presented 

 to the International Medical Congress at London a review of the 

 evidence on the specificity of protoplasm, which had been obtained 

 up to that time. For a list of papers on this subject, the reader is 

 referred to his inclusive bibliography. Later in that year Weigl 

 ('13) reported that homoiotransplants of skin in salamander lar- 

 vae retain their specific character, as far as color and markings 



