246 Kansas Academy of Science. 



Fourteen thyroidless tadpoles were found to have retained 

 their larval condition last September, while all of the control 

 tadpoles had metamorphosed by the 13th of August. The 

 thyroidless tadpoles continued to grow in size, but remained 

 absolutely stationary in their differentiation. A study was 

 made of the thyroidless tadpoles killed from time to time, and 

 most interesting facts were gained. 



One of my students, Mr. George Terry, made a study of the 

 skeletal system, and found that the vertebrae and the bones of 

 the limbs remained in that stage of development that they had 

 attained when the frog ceased to show further signs of meta- 

 morphosis. 



Another student, Mr. James Rogers, studied the effects of 

 thyroid removal upon the thymus and pituitary glands. He 

 found that the thymus gland in the thyroidless tadpoles con- 

 tinued to develop after it had ceased to grow in normal con- 

 trols. The pituitary gland reached at least full size in the 

 absence of the thyroid, and apparently grew even larger than 

 normally. These glands are all closely interrelated, and the 

 results thus obtained are of considerable interest. 



The most interesting feature was the development of the 

 gonads and germ cells. While the body as a whole remained 

 absolutely stationary in its stage of development, the germ 

 glands and germ cells developed almost normally. Ripe sperm 

 were found in tadpoles killed December 15 and February 7. 

 The ova continued their development until they were easily 

 visible with the naked eye. A comparison with the germ 

 glands of young frogs that had metamorphosed last summer, 

 and had undergone normal growth, showed no higher degree 

 of development than that found in these thyroidless tadpoles. 

 It is true that the latter had gonads a trifle smaller than those 

 of the normal frogs, but this is readily explainable upon the 

 basis of the smaller size of the body. The gonads are pro- 

 portionately as large in these thyroidless tadpoles as in the 

 control frogs of the same age. It is most significant that of all 

 organs studied, the germ glands alone have continued in their 

 development. 



This is very beautifully substantiated in a piece of research 

 carried out during the previous year by Mr. W. W. Swingle, 

 who under my direction studied the effects of thyroid feeding 

 upon the germ glands of tadpoles of this same species. He 



