GROWTH OF AMPHIBIA AFTER THYROIDECTOMY 



Showing that the removal of the thyroid from small frog larvae hastens their growth. 



Thyroidless larvae which do not have defects of the lower jaw or 



its muscles grow more rapidly than the controls 



R. sylvatica 



DATE OF OPERATION 



1916 



1917 



April 17. 

 April 9. 

 April 10. 

 Aprilll. 

 April 12. 

 April 14. 

 April 15. 

 April 27. 

 April 28. 

 April 30. 

 May 1 . . 

 May 3.. 

 May 5.. 

 May 6.. 



1918 



April 14. 

 April 22. 

 May 2.. 



Aver, max./ 1916-17. 

 or total \ 1916-18. 



EXCEED 

 CON. MM. 



AVER. 



Op. I Con 



17.015.0 

 18.518.0 



12.0 

 15.5 

 17.5 

 19.5 

 21.0 

 23.0 

 20.5 

 19.0 

 18.7 

 17.5 

 29.5 



11.5 

 14.5 

 17.0 

 19.0 

 19.0 

 20.0 

 19.0 

 17.0 

 16.5 

 18.0 

 29.0 



30.023.0 



38.032.0 



18.3 



17.2 



NUMBER 



WHEN OP. 



EXCEED 



CON. 



Op. I Con. 



10 



55 



29 13 



260 



218 



NUMBER 



WHEN 



CON. MET. 



LENGTH 



AT TIME 



WHEN CON 



MET. MM. 



Op. Con 



58 



Killed at 56 



Killed at 62 

 68 

 70 



68 

 67 



72 

 68 



72 



Killed at 65 

 Killed at 56 

 Killed at 48 



72 



N. B. — The 1918 larvae were not measured at the 18 to 20-mm. stage. The 5 /5 

 group of thyroidless larvae had defective jaws. Abbreviations: Aver., average; 

 Con., control larvae; Op., thyroidless larvae; iVx., not measured; Max., maximum; 

 Met., metamorphosis or metamorphosed. 



1 Only one of all the control larvae studied became over 50 mm. in length. 



