EEMOVAL OF THYMUS GLANDS — TADPOLES 197 



CONCLUSIONS 



1. The thymus glands from their very inception exert no 

 influence upon growth or upon the progress of metamorphosis. 



2. They are not at any stage of development indispensable to 

 life, nor does their removal appear to cause any marked defici- 

 ency in the general metabolism of the body. 



3. The extirpation of the thymus glands does not in any way 

 modify the quality or the rate and degree of development of the 

 gonads. 



4. A rather incomplete study of the thjrroid glands in the thy- 

 musless frogs fails to show that they were in any sense abnormal. 

 It is fair to conclude that the thymus glands exert no influence 

 upon the thyroid glands. 



5. No modification of internal features was seen to result from 

 the absence of the thymus glands. 



