1 Amblystoma. 

 8/15/16. X 9 



2 Amblystoma. 

 8/15/16. X 9 



Amblystoma. 

 Amblystoma. 

 Amblystoma. 

 R sylvatica 

 R. sylvatica. 



7 

 X20. 



8 R. sylvatica. 

 tomy. X 20. 



9 R. sylvatica. 



PLATE 1 



EXPLANATION OF FIGURES 



Control. Tot., 24 mm. Transverse section. 5/15 to 



Thyroidless. Tot., 30 mm. Transverse section. 5/15 to 



Control. Tot., 24 mm. Hypophysis. X 96. 

 Thyroidless. Tot., 30 mm. Hypophysis. X 96. 

 Control. Tot., 24 mm. Thyroid. X 96. 

 Control. Tot., 6.5 mm. 4/20/16. X 20. 

 Thyroidless. Tot., 6.5 mm. One hour after thyroidectomy. 



Thyroidless. Tot., 10.5 mm. Four days after thyroidec- 



Control. Tot., 10 mm. X 20. 



In stating the length of the animals. Tot. = total length. The dates given refer 

 to the date of the beginning of the experiment and the date of killing the animal 

 e.g., 5/15 to 8/15/16 = May 15th to August 15th, 1916. Abbreviations: ^., aorta; 

 B. v., blood-vessel; H., hypophysis; Mes., mesoderm; P.C, pericardial cavity; 

 Ph., pharynx., T., thyroid; X., location of thyroid in normal larvae. 



52 



