METAMORPHOSIS IN FROG LARVAE 



539 



limb buds had not increased in size; the tails of the larvae had 

 dwindled to half their original width of November 1. The 

 larvae were very sluggish and swam about only when violently 

 disturbed. April 8, 1916, five of these starved tadpoles were 



Fig. 10 Gonad of thyroid-fed larva. From animal shown in figure 9. 



started upon the thyroid-flour-paste diet; the remaining five 

 animals were fed corresponding amounts of flour paste without 

 the thyroid extract, and in addition, finely shredded pieces of 

 beef liver. 



At the end of the ten days, the thyroid-fed animals showed 

 indications of the typical thyroid reaction. Twenty days from 



