GROWTH OF AMPHIBIA AFTER THYROIDECTOMY 25 



As is shown by figures 36 to 39, the hypophysis is larger in 

 thyroidless larvae than in controls of the same size at the time 

 of metamorphosis. These figures represent fairly closely the 

 difference in size between the hypophyses of our control and 

 experimental larvae at this stage of their development. The 

 hypophysis and especially the inferior lobe may be considered 

 to have hypertrophied in the thyroidless larva as compared with 

 that of the control of the~sairre; size (figs. 36 and 38) . The differ- 

 ence is slightly greater than is indicated by the two drawings, 

 because the thyroidless larva (fig. 36) was slightly smaller than 

 the control (fig. 38). The difference, however, is much less than 

 that described by Rogers ('18), who endeavors to compare the 

 hypophysis (or part of it) of control larvae with that of thyroid- 

 less larvae much larger. His method of 'correction' for body 

 length introduces a large error into his figures, as noted above. 

 In Rogers' summary (p. 594) he states that after correcting 

 for difference in the size of the animals, the hypophysis of the 

 controls is represented by the figure 152 and that of the thyroid- 

 less by 776. This would indicate an hypertrophy in the latter 

 of some 300 per cent, a figure obviously incorrect. Rogers 

 leaves out of his summary (p. 594) the hypophysis of his thyroid- 

 less larva no. 4, with no explanation for an omission which 

 changes greatly the 'average volume' of this group, as this par- 

 ticular hypophysis is but little more than half the average volume. 

 The hypophysis of Rogers' control larva no. 10 (which is about 

 the same size as the thyroidless larva no. 9, p. 594) has nearly 

 one-half the Volume' of the hypophysis of the thyroidless animal. 

 The difference between these two is less than the difference 

 between the extremes in either group of larvae. As a matter 

 of fact, the hypophysis of the thyroidless larvae has less than 

 two times the volume of that of controls of the same size in our 

 experiments (figs. 36 and 38). If there were no real difference 

 at all between the two, Rogers' method of 'correction' would 

 still show an apparent difference in all cases in which the glands 

 of animals of different sizes were compared. 



In our larger thyroidless larvae, the hypophysis (fig. 42) is 

 relatively larger than in the smaller thyroidless larvae, so that 



