METAMORPHOSIS OF AMPHIBIAN ORGANS 279 



Second: if replacement of the graft actually takes place it is 

 easy to notice it macroscopically, without the aid of microscopic 

 sections. This was demonstrated by the behavior of the graft 

 in experiment 46. 



Third: certain individual differences between the yellow spots 

 of different individuals may help in determining the origin of 

 the yellow spots on the graft, as they reappear in the graft even 

 if the spots of the host are of a very different type from that of 

 the graft's spots. In such cases it is easy to distinguish between 

 the spots of the graft and the host. For instance in experiments 

 11-12, and experiments 21-22, there could have been no doubt 

 that the almost orange yellow spots did not belong to the host 

 but to the graft, even if the history of these spots were unknown. 

 The spots of all four hosts were of a faint yellow, and orange 

 yellow spots could not be found on their bodies except where the 

 graft had been made. As both grafts of each pair were taken 

 from the same individual we would expect them to develop the 

 same type of spots, which is what actually happened. The 

 results in experiment 33 are similar. 



Fourth: Weigl, 6 who also studied homoplastic grafts of 

 Amphibian skin, had experiences similar to ours concerning the 

 possibilities of replacement of the graft by the skin of the host. 

 According to his statements, the surrounding skin of the host 

 never grows over or into the grafted piece of skin nor does the 

 pigment of the graft spread into the skin of the host nor the 

 pigment of the host migrate into the grafted skin. 



The heteroplastic grafts behave very differently from the 

 homoplastic ones insofar as they are actually replaced by the 

 skin of the host, as will be described in another article. It will 

 suffice to mention here that this replacement did not interfere 

 with our experiments since it did not begin before the host had 

 left the water (except in experiment VI). The fact that in 

 some heteroplastic skin grafts, spots of the Punctatum type were 

 formed, in itself demonstrates that. the grafts were normal at 

 least to such an extent as to produce that phenomenon upon 

 which our conclusions are based. The same is true for the eyes 



6 R. Weigl, 1913, p. 597. 



