248 EDUARD UHLENHUTH 



III. THE EXPERIMENTS 



A. HOMOPLASTIC TRANSPLANTATION BETWEEN LARVAE OF 

 AMBLYSTOMA PUNCTATUM 



1 . Material and method 



The general method of these experiments should be to remove 

 one piece of skin from the larva just before the factor inducing 

 metamorphosis is developing in the body, and to graft the piece 

 to another larva in which this factof will not develop for a long 

 time. The animal from which the skin graft is taken should 

 metamorphose long before the piece of skin which was grafted 

 onto the young host would metamorphose, provided the meta- 

 morphosis of the skin follows the same rules as that of the eye 

 and gills. Grafting of a young skin to an old larva in which 

 the metamorphosis factor is just to develop should give a re- 

 sult opposite to that of the first mentioned experiment; meta- 

 morphosis of the skin graft should be accelerated and should 

 occur before the animal from which the graft was taken would 

 metamorphose. 



In order to use this method, it is necessary to have on hand 

 larvae whose age varies sufficiently to make it certain that with 

 a younger animal also, an earlier stage of development will corre- 

 spond, which relation according to a well known experience 

 exists in Amphibians, only if the individuals differ in age by 

 months. Since we used larvae whose age varied only by a few 

 days we had to modify our method. The new method was based 

 on the fact that in a lot of animals hatched on the same date, 

 the rate of development varies, sometimes to the extent of several 

 months, in spite of apparently the same treatment. It was 

 hoped then, that of two individuals chosen at random, one might 

 develop more rapidly than the other; by increasing the number 

 of pairs there would also be an increase in such pairs whose 

 individuals would develop unequally. Thus each experiment 

 consisted of two animals, X and Y (text fig. a), to each of them 

 one of the two eyes of a third animal A and the skin of the 

 corresponding half of the head of animal A was grafted. If 



