PLATE 2 



EXPLANATION OF FIGURES 



4, a to p Rana temporaria IV. Experiment II. a, control ; b, thymus; c, spleen ; 

 d, muscle (thyroid under 4, o and p) ; e, thymus-thyroid II ; /, thymus-thyroid III ; 

 g, thymus-thyroid IV; June 1, 1912. h, thymus-thyroid IV; /, thymus-thyroid V; 

 June 17, 1912. A", muscle; I, muscle-thyroid; to, spleen; n, spleen-thyroid; June 

 26, 1912. to p, 1 frog fed on liver, metamorphosing on July 12, and 5 pigmy 

 frogs, fed on thyroid metamorphosing on April 22, 81 days earlier, o, dorsal; p, 

 ventral view. 



7, a to 6 RanatemporariaVIII to XI. Experiment V. a, spleen; b, adrenal; 

 July 6, 1912. 



8, a to d Bufo vulgaris I. E>yjeriment VII. a, control ; b, muscle; c, thymus; 

 d, thyroid; June 6, 1912. 



9, a to r Bufo vulgaris III. Experiment X. a, original size; June 5, 1912. 

 b, control; c, thyroid-plants, thyroid given 1 day; (/, thyroid-plants, thyroid given 

 3 days; e, thyroid-plants, thyroid given 5 days; June 26, 1912. /, thyroid-muscle; 

 g, thyroid-plants (alternately); h, thyroid-thymus; i, thyroid-hypophysis; k. 

 thymus-plants; /, thymus-hypophysis; June 26, 1912. to, control; h, thyroid- 

 nmscle; o, thyroid-plants; p, thyroid-hypophysis; q, thymus-plants; r, thymus- 

 hypophysis; July 6, 1912. 



10, a to i Rana temporaria IV. Experiment II; compare figure 4, atop. 

 Thyroid-fed frogs, 16 to 18 days old, at the time of metamorphosis, figure 4, I. 



11, a to f. Tails of tadpoles fed on different substances, to show pigmenta- 

 tion; figure 4, /. a thymus; b, liver; c, spleen; d, muscle; c, adrenal cortex; /. 

 adrenal medulla. 



478 



