FEEDING EXPERIMENTS ON TADPOLES 435 



May 14 To this time the controls have been starving, in order to test 



the possible influence of hunger on development. They 



show no signs of advancement, but are far behind in size. 



From now on they are fed on Elodea canadensis. 



A group originally intended for a hypophysis diet also starved 



up to this day, and from now on is fed on brain. 

 The liver-fed ones have a greenish color, the thymus-fed ani- 

 mals are deep black. 



May 24 The smallest individuals in all sets begin to die off. The 

 spleen-fed ones become very black, the bigger ones on ad- 

 renal cortex become very light, lighter than on adrenal 

 medulla. 



June 12 The first liver-fed ones show hind legs; this is 49 days later 

 than the time at which the thyroid-fed ones attained the 

 same condition. 



June 14 Hind legs appear in adrenal-cortex-fed tadpoles. Their body 

 assumes a peculiar triangular shape (fig. 7 6), very pointed 

 at the anterior end and broad at the posterior. They are 

 all becoming light, while all the adrenal-medulla-fed ones 

 are dark. 



June 17 A number of each group, 70 to 80, which have no hind legs 

 except the small buds, are placed on thyroid diet. 



June 19 The light color of the adrenal-thyroid tadpoles is disappear- 

 ing. 



June 20 Those liver-fed ones that have put out fore legs since June 

 12 shorten their tails. 

 The liver-thyroid animals develop hind legs. 



June 21 Adrenal medulla-thyroid and muscle-thyroid tadpoles de- 

 velop hind legs. The former are extremely active. 



June 22 Liver-thyroid and muscle-thyroid ones assume a frog shape. 



June 23 Spleen-thyroid and adrenal cortex-thyroid ones develop hind 

 legs. The first liver-fed frog leaves the water. 



June 24 Spleen-thyroid and adrenal cortex-thyroid animals assume 

 frog shape. Brain-thyroid ones develop hind legs. Ad- 

 renal cortex tadpoles are extremely light greenish-yellow. 

 Brain-fed ones assume somewhat the triangular adrenal cor- 

 tex shape described on June 14. 



June 25 Liver-thyroid and adrenal medulla-thyroid animals show fore 

 legs. 



June 26 Spleen-thjToid-fed ones show fore legs. 



Ovary-thyroid and brain-thyroid tadpoles assume frog shape, 

 the latter are very active. 



June 27 Muscle-thyroid animals show fore legs. 



June 29 Adrenal eortex-thyroid and brain-thyroid ones show fore legs. 



June 30 Ovary-thyroid ones show fore legs. 



July 6 All the thyroid-fed ones are fixed, since many of them die. 



July 7 Brain-fed tadpoles show hind leg buds. 



