FEEDING EXPERIMENTS ON TADPOLES 443 



June 19 All thymus-thyroid V die, thyroid had been placed in the 



water every day. 

 June 20 Thymus-thyroid VI have hind leg buds. 

 June 21 Muscle-thyroid have hind leg buds. 

 June 24 Spleen-thyroid have hind leg buds. 

 June 25 Thymus-thyroid VI and muscle-thyroid groups have fore leg 



buds. 

 June 26 Spleen-fed tadpoles have hind legs. 

 June 27 Spleen-thyroid group have beginning fore legs. 

 June 8 Thymus group have hind leg buds. 

 June 29 Control tadpoles have hind leg budsi 

 July 3 Last animal of the thymus-thyroid III group dies. 

 July 6 Last indi\dduals of the muscle-thyroid and spleen-thyroid 



animals are preserved. 

 July 10 The remaining thymus-j/hyroid VI are preserved. 

 July 14 Last one of the thymus-thyroid IV group dies. 

 July 20 The experynent is discontinued. 



The muscle-fed tadpoles are best differentiated. 



Since Experiment III was performed along the same lines as 

 Experiment II, it may be well now to give the data of Experiment 

 III and discuss the two groups together. 



Experiment III 



Rana temporaria, Set III. Figure 3, a to n. Contained apparently 

 three lots of eggs mixed; they hatched April 7 to 8 and the feedings 

 began April 13, 1912. The original lengths of the tadpoles were from 

 10 to 11.5 mm. 



The experimental data are as follows: 



April 13 Food is placed in the dishes for the first time. 



April 15 Food is first taken by the animals. 



April 18 Thymus-fed specimens become darker in color. 



April 20 Some of the muscle- and thymus-fed tadpoles show hind leg 



buds. 

 j\Iay 6 Part of the thymus-fed animals changed to thyroid diet, 



thymus-thyroid I. 

 May 10 All individuals of the thymus-thyroid I group have hind legs 



and the frog shape is noticeable. 

 ;May 13 Thymus-thyroid I group have fore legs budding, the left one 



first. They lie on their backs and breathe rapidlj-. 

 A second group of thymus-fed animals is put on thyroid, thy- 

 mus-thyroid II. 

 May 15 The control has not yet been fed. It remains far behind the 



other groups in size and shows no signs of differentiation. 



From now on the control group is fed on Elodea canadensis. 



