METAMORPHOSIS OF AMPHIBIAN ORGANS 255 



and as the animal died soon after being set on land-condition 

 it was not possible to watch the process of clearing up. 



In the pair 19 and 20 the grafts of both animals did not de- 

 velop spots and also did not show any network, but in both 

 animals the changes of the background progressed simultane- 

 ously. When the animals died (September 19) they were pre- 

 served in formalin; from the formalin specimens it can still be 

 seen that in both animals graft and host are at the same stage of 

 development. Unfortunately, as both hosts had developed at 

 the same rate, this pair does not permit of any conclusions con- 

 cerning the determination of the metamorphosis of the grafts. 



In pair 23 and 24 both grafts were spotless pieces of skin. They 

 nevertheless developed a network; but as both animals X and Y 

 formed their network at the same time the grafts also develop- 

 ing simultaneously with their respective hosts, also formed the 

 network at the same time and there was no way of knowing 

 whether the formation of the network was determined by the 

 hosts X and Y or by the animal A from which both grafts were 

 taken. In experiment 23 the graft developed a little spot under- 

 neath the eye just at the same time that the host's network 

 separated into yellowish green spots. This little spot soon dis- 

 appeared. In experiment 24 however, no spots developed at all 

 except a faint little patch of tiny pigment dots believed to be 

 seen for only two days on the hind corner of the graft, about 1 

 month after the host's network had separated into spots. It is 

 however impossible to draw any conclusions from these 2 experi- 

 ments. 



In experiments 29 and 30 the graft of animal X (experiment 29) 

 never developed any spots, while the graft of animal Y never 

 formed a network; so there was no way of comparing the two 

 experiments with each other. It may be mentioned however, 

 that in experiment 29 the network of the host appeared simul- 

 taneously with that of the graft (August 14) and that in experi- 

 ment 30 host and graft formed their spots at the same time. 



In the pair 35-36, network and spots of host and graft were 

 formed simultaneously in experiment 35, but the graft of experi- 

 ment 36 was a piece of skin which did not develop spots, the 



