I 4 6 



E. UHLENHUTH. 



FIG. i. Control larva 134 days after the beginning of the experiment. 

 Note the shortened gills and the almost complete absence of the anterior 

 portion of the ventral fin. 



FIG. 2. Iodine-fed larva 134 days after the beginning of the experiment. 

 Note the long gills and the completeness of the fin. This larva, although large 

 amounts of inorganic iodine were administered to it, is less far advanced 

 towards metamorphosis than the control animal. 



FIG. 3. An animal to which iodothyrin was administered, photographed 

 134 days after the beginning of the experiment. This animal metamorphosed 

 13 days after the first administration of iodothyrin; it was a completely 

 metamorphosed terrestric salamander when the photograph was made, and had 

 been so several months before it was photographed. 



