442 J. F. GUDERNATSCH 



April 21 The thyroid individuals are budding fore legs, the left one 



first ;^ 16 days old. 

 April 22 Thyroid ones begin to die. 



Only 3 days after the thymus-fed ones were changed to 



thyroid the influence is noticeable. They have become 



reduced in size, take on frog shape and bud hind legs. 

 April 23 Fore legs budding after a treatment of only four days. Thy- 



mus-thyroid I do not seem as frail as animals fed on thy- 

 roid alone. 

 April 25 ThjToid-fed anjmals do not develop their limbs any further, 



nor do they reduce their tails much further since last ob- 

 served; progress has ceased. 

 April 29 The last thyroid and thymus-thyroid I fed animals die. 

 May 6 A second group of thymus-fed animals is changed to thyroid, 



thymus-thyroid II. 

 May 9 Thymus-thyroid II have hind legs appearing and the frog 



shape is noticeable. 

 May 10 Thymus-thyroid II have fore legs budding out, the left one 



first. 

 May 13 A third group of thymus-fed animals is changed to thyroid, 



thymus-thyroid III. 

 May 15 The control animals have not been fed so far. They do not 



show any sign of differentiation and very little growth. 



From now they are fed on Elodea canadensis. 

 May 18 All thymus-thyroid II have both fore legs. 



Thymus-thyroid III have hind leg buds. 

 May 22 All thymus-thyroid III have their hind legs well developed. 

 Other thymus-fed animals changed to thyroid, thvmus-thy- 



roid IV. 

 May 28 Thymus-thyroid III have fore legs. 

 Thymus-thyroid IV have hind legs. 

 June 2 Thymus-thyroid IV have fore legs. 

 June 5 Thymus-thyroid II begin to die. 

 June 6 Some muscle-fed tadpoles have hind legs beginning. 

 June 7 Another group of thymus-fed animals put on a thyroid diet, 



thymus-thyroid V. 

 June 12 Thymus-thyroid V have hind legs beginning and the frog 



shape faintly noticeable. 

 June 17 Again a group of thymus-fed tadpoles changed to thyroid 



diet, thymus-thyroid VI. 

 Part of muscle and spleen fed animals put on a thyroid diet, 



muscle-thyroid and spleen-thyroid. 

 June 18 Last thymus-thyroid II dies. 



The members of the thymus-thyroid V group have fore leg 



buds. 



1 Barfurth states that in 80% of the tadpoles the right fore leg appears first. 

 I have always observed the opposite. 



