PLATE 1 



EXPLANATION OF FIGURES 



9 Brain of a tadpole of 27 mm. body length and 62 mm. total length. 



10 Brain of recently metamorphosed frog with body length of 24 mm. 



11 Brain of young frog, 51 mm. body length. Killed February 22. 



12 Brain of thyroidless tadpole with body length of 43 mm. and total length 

 of 123 mm. Killed February 7. 



518 



