FEEDING EXPERIMENTS ON TADPOLES 453 



The tadpoles which again received muscle after the thyroid 

 treatment reacted more strongly to the stimulus than those put 

 on a vegetable diet. They all grew hind legs within from 1 to 

 5 days, the frog shape became noticeable very soon, and they 

 died in great numbers, so that 7 days after the beginning of the 

 experiment only 20 per cent were alive. The animals treated 

 from 3 to 5 days grew fore legs on the 8th day, those treated 2 

 days were all dead on the 9th day; this group was affected most 

 strongly, which may be a mere coincidence. The groups fed only 

 one day grew fore legs on the 42d day, at this time only four 

 of this group were alive, only one of the 3 day group, artd none 

 of the '4 and 5 day groups, the last ones having died on the 29th 

 day of the experiment. That is, out of 400 individuals only 4 

 in the 1 day group and 1 in the 3 day group were able to survive 

 the thyroid shock. The table of growth on page 450 shows that 

 these surviving individuals actually begin to grow again. These 

 4 animals of the 1 day group seem to have absorbed a very small 

 quantity of the thyroid agens. They stop their precocious dif- 

 ferentiation very soon and do not grow fore legs until July 17, 

 which is 34 days later than the 3 and 5 day groups. 



The second set of tadpoles, those put on a vegetable diet after 

 a thyroid treatment, reacted in a similar fashion to that just de- 

 scribed, except perhaps as stated above, they were somewhat less 

 affected. This might suggest that a meat free diet may help to 

 counteract thyroid influences. The 3 and 5 day groups grow 

 hind legs on the 5th day of the experiment, the 2 day group on 

 the 6th day, and the 1 day group not until the 14th day. Fore 

 legs appear in the 3, 4 and 5 day groups on the 10th day, in the 

 2 day group on the 9th day, in the 1 day group none had ap- 

 peared on the 46th day, when the experiment was discontinued. 

 While many animals died during the first few days, some were 

 able to keep alive. On the 27th day the last ones of the 5 day 

 group died, and on the 33d day all of the 2 and 3 day groups 

 were dead. There were five of the 1 day group and one of the 

 4 day group alive on the 42d day. These, as the table of 

 growth of page 450 shows, start again to grow. 



