536 



w. w. SWINGLE 



was 346 mm. The alimentary tract was simply a long coiled 

 tube, with no differentiation into stomach, small and large 

 intestine. When one pauses to consider that in the short space 

 of two weeks or so the gut of the thyroid-fed larvae actually 

 decreased 246 mm. in length, and differentiated from a long 

 coiled tube into a stomach, a small intestine and a large in- 

 testine, one is astonished indeed (figs. 8 and 9 ] . 



Fig. 7 Photograph of same series of animals as shown in figure 6. 



Macroscopic examination of the gonads of both experimental 

 and control larvae, revealed considerable variation in regard to 

 the size of the glands among the animals of each series. Only 

 animals of the same sex were compared. The germ glands of the 

 thyroid-fed larvae were slightly smaller than those of the control 

 animals. In female tadpoles, a comparison of the ovaries of 

 the normal and thyroid-fed animals showed fewer convolutions 

 in the glands of the thyroid series. The number and depth of 



