May 6. A number of the thyroid-fed were dying, and the skin and opercular membranes were swollen out away from the tissues beneath.
Largest normal tadpole, 2.7 cm. long.
body, 1.0 "
tail, 1.7 "
Largest thyroid-fed tadpole, 1.1 cm. long.
body, 0.5 "
tail, 0.6 "
May 10. A great number of the thyroid-fed dead and the rest dying, lying at the bottom motionless. They now had the tail much shorter, and the fore-legs showing as well as the hind, but the latter not very long, and without joints or toes.
Period from first feeding with thyroid, thirty days. I now decided to feed the controls with thyroid, expecting that as they were large and vigorous they would have strength enough to complete the metamorphosis and become frogs.
May 15. Fed the controls with thyroid for first time.
The smallest of them was in total length 1.7 cm.
body, 0.7 "
tail, 1.0 "
The largest measured was in total length 2.2 "
body, 0.8 "
tail, 1.4 "
May 25. All but two of the tadpoles dead. The tails were only half the original length, all had well-developed hind-legs, some with toes, but the fore-legs were beneath the opercula, not projecting from the surface.
Smallest total length, 1.2 cm.
body, 0.5 "
tail, 0.7 "
Largest total length, 1.8 "
body, 0.7 "
tail, 1.1 "
These last measurements were made after the tadpoles had been preserved in spirit, and were therefore doubtless somewhat less than in the fresh condition. Making allowance for this it is evident that the tails had undergone reduction as part of the metamorphosis, but the body was also shorter. There is some reason therefore for concluding that actual reduction in size of body occurs as the result of metamorphosis induced by thyroid feeding. As in the other case the skin and opercular membranes were distended by liquid beneath them.
The total period of the change in this second experiment was ten days.