PLATE 9 



EXPLANATION OP FIGURES 



31 (a) Ventral and (b) median views of a model of the left thyroid of a 38/3.5 

 normal frog tadpole (specimen 15). Liver diet. Fixed 63 days after the operative 

 stage. X89. 



32 (a) Ventral and (b) median views of a model of the left thyroid of a 43/0.1 

 albino frog tadpole (specimen 18). Liver diet. Fixed 101 days after epithelial 

 hypophysectomy. X89. 



130 



