466 J. F. GUDERNATSCH 



The main interest of Experiment X lies in the results following 

 the mixed feedings of two kinds of animal tissues or animal tis- 

 sue and plants. 



It will be seen from the notes that, whenever thyroid tissue 

 was one of the two foods it exerted an accelerating influence on 

 development. The four groups fed on thyroid-thymus (fig. 9 h), 

 thyroid-muscle (fig. 9/, 9 n), thyroid-hypophysis (fig. 9 i, 9 p) 

 and thyroid-plants (fig. 9 g, 9 q) developed their hind legs on the 

 5th day. The fore legs appeared in the third and fourth groups 

 on the 21st day, in the second group on the 22d day and in the 

 1st group on the 24th day and the tadpoles of the several groups 

 began to metamorphose in the same order. These facts indicate 

 that the thymus was best able to counteract the thyroid, the 

 h^-pophysis and plants least. It is peculiar, however, that the or- 

 der of the last individual metamorphoses is exactly the reverse, 

 the thyroid-thymus group completing the change first, the thy- 

 roid-plant group last. It is doubtful whether this has any con- 

 nection with the fact that the greatest reduction in size was in 

 the first group and gradually less down to the fourth. 



We may now compare these thyroid-thymus results with those 

 of Experiments VIII and IX. They are essentially alike, the 

 thymus always being able to check the thyroid influence to some 

 degree, but unable to suppress it entirely (fig. 2 k, 2 m, 6 6, 6 c?, 



9/7.). 



The remaining three groups, thymus-hypophysis (fig. 9 i, 9 p), 

 thymus-plants (fig. 9 k, 9 q) and hypophysis-plants run much 

 slower than the corresponding thyroid groups. Their hind legs 

 appear from 16 to 19 days later than in the thyroid combination 

 feedings. 



The hypophysis-plant group leads the three, the thymus-plant 

 group is a few days behind. This corresponds to the thyroid 

 groups, where the hypophysis was less able to counteract the thy- 

 roid acceleration than was the thymus. In the thymus-hypophy- 

 sis group (9 I, 9 r) two retarding factors combine, therefore the 

 tadpoles fed on this diet never develop fore legs nor do they be- 

 gin to metamorphose. Yet they are very big healthy specimens. 



