528 



W. W. SWINGLE 



shortened in the fourteen day interval of the experiment in the 

 thyroid-fed group as contrasted with their controls: 



Microscopic examination of the gonads and germ cells re- 

 vealed no observable differences between those of the thyroid- 

 fed and control larvae. This is rather striking, considering the 

 very great bodily changes rapidly taking place in those animals 

 given the thyroid diet. Even in the case of animals in which 

 metamorphosis had reached an advanced stage, there were no 

 changes in the condition of the gonads and germ cells observed, 

 differing from their controls. Body metamorphosis, in other 

 words, had not affected the germ glands or germ cells in any 

 way. 



On May 8, 1915, eighty larvae, averaging 25 mm. in length 

 vvere divided into two lots of forty each; one for thyroid feed- 

 ing, the other to serve as controls. The feeding began the same 

 day. 



May 16, the typical changes of hyperthyroidism made their 

 appearance in all of the thyroid-fed larvae. The feeding was 



