44 E. R. HOSKINS AND M. M. HOSKINS 



in July, so it is probable that those of the frogs would have done 

 so had these animals been kept alive. Hence the difference in 

 the rate of development of the testes between the 1917 and 1918 

 animals was not proportional to the difference in time required 

 for their development. This compromise indicates that while 

 the testes in their development are not independent of the body, 

 nevertheless they are not entirely dependent upon the rate of 

 differentiation of the body as a whole. 



In the larger 1917 thyroidless larvae killed in July, 1918 (fig. 

 93), the testes were relatively larger than in the control larvae 

 of the stage just preceding metamorphosis. The testes there- 

 fore grow relatively more rapidly in the larger than in the smaller 

 animals, but differences exist in the rate of growth of various 

 other organs at different periods of any animal's life, so this is 

 not characteristic of the gonads alone. Moreover, a part of the 

 great increase in the size of the testes is due simply to an ex- 

 pansion of the tubules that does not represent additional testicular 

 tissue. In this expansion the volume increases more than the 

 weight of the testes and prevents accurate comparisons where 

 volumes only are considered. 



In age alone the thyroidless larvae are sexually precocious 

 because their gonads develop much more rapidly than those of 

 the controls, but since the entire body grows still more rapidly 

 than the controls it might be argued that this is not true sexual 

 precocity, even through the animals remain in the larval form. 



Normally, synapsis occurs in the testis some weeks after meta- 

 morphosis (Swingle, '18). In our 1917 animals it had begun in- 

 many of the thyroidless larvae of the same age as the controls 

 at metamorphosis, but these thyroidless larvae were considerably 

 larger than the control larvae ever became and hence are not 

 directly comparable with them. In thyroidless larvae of the 

 same size as the controls (but younger) the condition in the 

 testis was the same in both groups, the growth of the testis thus 

 tending to keep pace with the body growth, as does that of 

 other organs. Swingle ('18) noted that inanition retards both 

 bodily and sexual differentiation in frog larvae. The testes do 

 not differentiate in starved animals for the reason that the larvae 



