THYROID REMOVAL IN LARVAE OF RANA PIPIENS 



503 



ping from a tap. The Lawrence city water is very hard with 

 584 mg. of solids per litre. 



On June 10 both the thyroidless tadpoles and the controls hav- 

 ing reached a length of 35 to 40 mm. showed further unfavorable 

 effects that I have attributed to the quality of the city water. 

 This consisted in a lateral twisting of the tail that constituted a 

 marked deformity. It should be kept in mind that this was 



Text fig. 2 Photograph taken August 6. A, Undersized thyroidless tadpole; 

 B, large thyroidless tadpole with body length of 34.5 mm. The twist of the tail 

 is abnormal. It is discussed in the text. C, a metamorphosed control; D, 

 metamorphosed operated tadpole. Section of the head showed that there had 

 been incomplete removal of the thyroid gland. A sufficiently large thyroid 

 gland had developed to produce metamorphosis. 



equally true in both the operated and the control specimens and 

 hence was not in any sense attributable to the absence of the 

 thyroid. It appeared at the time when the mortality was 

 greatest. I have never seen such distortions of the tail in the 

 case of tadpoles kept in a normal w r ater supply. 



This modification affected only the tail and did not in any 

 degree hinder the metamorphosis of the controls, although many 

 of them showed extreme distortion of the tail. 



