THYROID REMOVAL IN LARVAE OF RANA PIPIENS 



511 



prevented normal activity in securing food. Taking all of these 

 features into consideration, we are justified in considering the 

 testes of the thyroidless tadpoles to be roughly equivalent to those 

 of the normal frogs that had metamorphosed the summer before. 

 A tadpole that was starved during the summer, only being 

 fed sufficiently to keep it alive, was fed sparingly from the middle 

 of November up to February 22, when it was killed. It was 

 found to have food in the intestinal tract. The body length was 

 27 mm. and the total length GO mm. The legs were 5 mm. long. 

 It had retained the great length of the alimentary tract character- 

 istic of tadpoles, but the gonads were very poorly developed and 



Text fig. 4 Transverse section of a testis of a thyroidless tadpole killed Feb- 

 uary 7. 



Text fig. 5 Transverse section of a testis of a young, sexually mature frog 

 51 mm. body length. Killed February 22. 



Text fig. 6 Transverse section of a testis of an unoperated, starved, control 

 tadpole, 27 mm. body length. Killed February 22. 



thus in sharp contrast to those of the thyroidless tadpoles. The 

 total volume estimates for the testes of this specimen are 0.0419 

 mm. and 0.0581 mm., an average of 0.0500 mm. Compare this 

 with the volume estimate of the thyroidless tadpole killed Feb- 

 ruary 7. Here the volume estimates for the testes are 0.9333 

 mm. and 0.8835 mm. with an average of 0.9084 mm. The latter 

 estimate is roughly 18 times as large as the average testes of the 



