FEEDING EXPERIMENTS ON TADPOLES 433 



used for the different experiments, but this was of no importance, 

 so long as the tadpoles used for one experiment were kept under 

 uniform conditions. 



As during the previous year, the food in small pieces was placed 

 in the water and there voraciously taken by the animals, with 

 the exception of pancreas which never seemed to excite their 

 appetite very greatly. 



Last year the tadpoles had their natural food previous to the 

 experiments, this year in all but one experiment no other food was 

 received except the one chosen for the studies. In 1911 after 

 the feeding began the animals were kept exclusively on a one- 

 gland diet; in 1912 these experiments were repeated with part 

 of the animals while in addition a mixed, either two-animal tis- 

 sues or gland-plant diet, was introduced. 



The following were used as foods: thyroid, adrenal, liver, 

 spleen, hypophysis, brain, pancreas and muscle from the horse, 

 testicle, ovary and thymus from cattle, and as vegetable food 

 Elodea canadensis and Ceratophyllum demersum. 



It would not have been possible to perform such an extensive 

 series of experiments but for the courtesy and generosity of Prof. 

 S. Mollier, in whose laboratory in Munich the experimental part 

 of this paper was carried out. It is with pleasure that I express 

 my best thanks for the many kindnesses shown me during my 

 stay in his laboratory. 



Experiment I 



Rana temporaria, Set I. Figure 1, a to zf. Hatched April 4 to 7, 

 1912. Feeding began April 13, 1912. Original size 10.2 to 12 mm. 



The diary reads as follows : 



April 4 The feeding begins. 



April 22 Thyroid-fed have hind legs forming. 



April 24 ThjToid-fed have fore legs forming. 



April 25 Thyroid-fed begin to die off. 



April 29 Last thyroid-fed animals dead. Thymus- liver- spleen- and 



muscle-fed tadpoles are larger than the other groups. 

 April 30 Muscle, liver and spleen ones show hind leg buds. 

 May 4 Adrenal cortex, adrenal medulla and ovary have hind leg 



buds faintlv noticeable. 



