26 E. R. HOSKINS AND M. M. HOSKINS 



a still greater hypertrophy seems to be indicated than in the 

 hypophysis of the smaller animals, and especially is this true 

 of the inferior lobe. The shape of these larger hypophyses varies. 

 In some specimens the superior lobe is not so completely covered 

 by the inferior as in figure 42, and this increases the irregularity 

 of the outline of the gland and also the error in any attempt to 

 estimate its volume by multiplying together its three principal 

 diameters. This irregularity is indicated in figure 44 of the 

 hypophysis of a thyroidless larva that survived the second season. 

 In such older larvae the large proportions of the hypophysis 

 (fig. 44) are pretty well maintained; but we have autopsied only 

 three of these specimens, and their hypophyses are quite variable 

 in size, so we cannot be certain whether or not there is any further 

 change in the relative volume of the gland during the winter 

 and second spring and summer. The three hypophyses just 

 referred to are, however, all smaller than those of much younger 

 larvae of the same size. 



It cannot be determined how much of the overgrowth of the 

 hypophysis in larger thyroidless larvae is a true hyperplasia, 

 because of the lack of a proper basis of comparison. If the 

 control larvae could in any way be induced to grow as large as 

 these larger thyroidless larvae, their hypophyses might also be- 

 come relatively larger than those of smaller tadpoles. It is well 

 known that the relative size of most organs of an animal changes 

 as the animal becomes larger, and age changes also are evident. 



In a given time the body of the thyroidless larva becomes 

 larger than that of the control and its hypophysis increases 

 greatly in size, but it must be admitted that the great increase 

 in the size of this organ may be due to the factors' causing over- 

 growth of the entire body rather than that the reverse is the 

 case. However, from what is known in other animals and from 

 the fact that the hypophysis in the larger thyroidless larvae is 

 relatively larger than in the smaller thyroidless or control larvae, 

 it is probable that the overgrowth of the hypophysis accounts 

 partly at least for the overgrowth of the body as a whole. 



As stated above, the principal lobe of the hypophysis appears 

 to be the inferior. This lobe is actually wedge-shaped, as in- 



