180 
of the dorsal fin, reduction of the caudal fin, shrinkage of the giils 
and change of the form of the head) but in all cases the meta- 
morphoses were completed after certain intermissions. 
Observations of this kind might suggest that the artificially en- 
forced metamorphosis in the axolotl is going on in two phases 
which — provided the resorption of the thyroid preparations (or 
other effective iodine compounds) has been sufficient — run into 
each other without traceable bounds. The resorption of a certain 
minimum dose, on the other hånd, might initiate a partial meta¬ 
morphosis characterized through certain definite changes which can 
be permanent. 
30-2-1920. 
