PLATE 9 



EXPLANATION OF FIGURES 



R. sylvatica. Testes 



104 A, T. S. Control larva at beginning of metamorphosis (July 29, 1917). 

 X 34. B, same, showing beginning of tubule formation, but no synapsis. X 240. 



105 A, T. S. Young control frog. X 34. B, same. X 240. 



106 A, T. S. Thyroidless larva larger but of same age as larva of figure 

 104. X 34. B, same, showing advance in tubule formation, but no synapsis. 

 X 240. 



107 A, T. S. Large thyroidless larva, killed four months after thyroidectomy 

 (August 20, 1917). X 34. B, same, spermatogenesis begun. X 240. 



108 A, T. S. Large thyroidless larva, six months after thyroidectomy. X 34. 

 B, same, showing spermatozoa in tubules. X 240. 



109 Large thyroidless larva one year older than that shown in figure 106. 

 Shows fully matured testis. V. E., efferent tubule leading into kidney and con- 

 taining spermatozoa. X 34. 



