FEEDING EXPERIMENTS ON TADPOLES 



439 



To show the different degrees of response to the thyroid food 

 in the various groups, table 2 may be added. While it does not 

 reveal, as said before, any important points as to the respective 

 value of the different foods given before the thyroid diet, it shows 

 some striking changes. in the .subsequent positions in the series 

 of the various groups, especially those fed on adrenal medulla, 

 spleen and adrenal cortex. 



Experiment II 



Rana temporaria, Set IV. Figures 4, a to p. The tadpoles hatched 

 on April 5 to 6, and the feedings began April 13, 1912. Original length 

 of the specimens was 12 to 12.5 mm. 



The diary records of the experiment are given below: 



April 13 The feeding was started. 



April 16 Those fed on thymus and spleen have become larger than 

 the others. 



April 17 Thyroid-fed tadpoles have become considerably smaller than 

 thymus-fed ones and the thymus ones are getting dark. 



April 18 Thymus-fed tadpoles are much darker than the others, spleen- 

 fed specimens are also getting dark. Thyroid ones now show 

 frog-like bodies. 



April 19 Thymus-fed individuals are almost black, spleen-fed very 

 dark, muscle-fed much lighter, thyroid-fed darker than 

 muscle, but lighter than thymus and spleen. Thyroid ones 

 have distinct frog shape, their hind legs are beginning to 

 bud (14 days old). 



One set of thymus-fed individuals is now changed to a 

 thyroid diet, thymus-thyroid I. 



April 20 The resorption of the tail in thyroid-fed individuals is dis- 

 tinctly noticeable. The specimens all lie on the bottom of 

 the dish and appear frail, taking no more food, while the 

 others in the experiment swim actively. 



