254 EDUARD UHLENHUTH 



In experiment 18 host and graft had become quite dark yel- 

 low brown on August 28 and on this -day both had developed 

 greenish spots. After the animal was set on land-condition 

 '(September 1) host and graft turned continuously darker and 

 their spots grew more yellow. Finally, when the spots of the 

 host began to brighten up the graft lost its spot, but its back- 

 ground changed simultaneously with the host into a clear black. 



Though in five of these experiments — the sixth will be referred 

 to later — the graft metamorphosed simultaneously with the 

 host, the result is of course, not conclusive, as none of these 

 grafts was controlled by the other animal of the pair, which 

 carried the other half of the skin of the head of animal A; it 

 could therefore be possible that the animal A from which the 

 grafts were taken would have metamorphosed — if living — at the 

 same time as the respective new hosts. Hence the time of 

 metamorphosis in the grafts might have been determined by the 

 animals from which the grafts were taken and not by the new 

 hosts. On the other hand, the results obtained by these ex- 

 periments are not contradictory to the idea that metamorphosis 

 of the grafted organs is governed by the body of the host and 

 might be even explained on the basis of this rule in case a number 

 of other conclusive experiments could be shown to prove the 

 existence of such a rule. 



2. In 6 pairs (experiments 15 and 16, 19 and 20, 23 and 24, 

 29 and 30, 35 and 36, 37 and 38) both animals lived long enough 

 to metamorphose, but the results were not conclusive for some 

 other reasons. In some of them either the graft or the host did 

 not develop spots, while in others both hosts metamorphosed 

 at the same time, and still in some other experiments the ob- 

 servations made during the development of the skin were not 

 complete enough. 



In pair 15 and 16 the graft of experiment 15 did not develop 

 either network or spots ; nevertheless it developed simultaneously 

 with the host as indicated by the notes on the changes of the 

 background, and after metamorphosis cleared up into black at 

 the same .time that the host's skin did. In experiment 16 the 

 notes on the development of network and spots are incomplete 



