446 J. F. GUDERNATSCH 



May 18 The thymus-thyroid I animals are hardly able to swim; when 

 disturbed they move for a few seconds with convulsive 

 jerks, then drop again to the bottom of the dish. 



May 19 The thymus-thyroid II group (fed thyroid three times only, 

 May 13, 14 and 17) have hind legs and the frog shape 

 becomes noticeable. 



May 22 A third group of thymus-fed animals put on thyroid, thymus- 

 thyroid III. 



May 27 Thymus-thyroid II have fore leg buds. 



May 28 Thymus-thyroid III (fed four times on thyroid, May 22, 23, 

 25 and 26) have hijid leg buds. 



June 2 Thj^mus-thyroid III have fore leg buds. 



June 7 A fourth group of the thymus-fed tadpoles are put on thy- 

 roid, thymus-thyroid IV. 



June 9 The last specimens of the thymus-thyroid I group are dying. 



June 12 The thymus-thyroid IV animals have hind leg buds and the 

 frog-shape is noticeable. 



June 17 A fifth group of the thymus fed animals is changed to a thy- 

 roid diet, thj'mus-thyroid V. 

 Also some of the muscle-fed ones are put on thyroid. 



June 18 The thymus-thyroid IV animals have fore legs, but these 

 specimens are dying. 



June 20 Last of the thymus-thyroid II are dying. 



June 21 Thymus-thyroid V have hind legs. 



June 25 Thymus-thyroid IV have fore legs. 



June 26 The muscle-thyroid animals have hind legs. 



June 30 The muscle-thyroid animals have fore legs. 



July 1 A group of thymus-fed specimens put on a liver diet. 



July 4 Some of the thymus-thyroid III group that have been kept on 

 vegetable food since June 5 seem to recover from the thy- 

 roid influence. 



July 7 The last thymus-thyroid V are dying. 



July 14 Muscle-fed tadpoles grow hind legs. 



July 20 The experiment is discontinued, and only the muscle-fed ani- 

 mals have extremities. 



Experiments II and III were performed for the purpose of de- 

 termining whether tadpoles of different ages would react to the 

 thyroid diet in similar or different ways. For this purpose a 

 great number of tadpoles were kept on a thymus diet and groups 

 of these were changed to a thyi'oid diet at various times. Table 

 5 shows the time of reaction to the thyroid stimulus in the differ- 

 ent groups. The number of days in the first columns indicates 

 the respective ages of the animals at the start of the thyroid feed- 



