48 
L. Kaufman: 
normal secretion of the thyroid gland. The question arises whether 
the prominence of the eyes in transformed amphibians is produced 
by a definite substance which passes to the blood from the thyroidea. 
From investigations published by Iscovesco it is known that by 
means of acetone it is possible to extract lipoid from the thyroid 
gland, causing exophthalmus that lasted several minutes, when the 
lipoid was injected into the blood of guinea-pigs. The rest of the 
thyreoidea. as shown by Fassin, is the active substance connected 
with iodine. If the shape of transformed amphibians' eyes is caused 
by the substance extracted by means of acetone and not correlated 
to other morphological characters of the terrestrial animal, it would 
be possible to produce prominent eyes in larvae on feeding them 
with the lipoid; and, on the other hand, to obtain terrestrial 
Amblystomata with larvally shaped eyes, by giving them thyroidine 
deprived of that substance. 
Petri k’s investigations seem to favour the view that the ap¬ 
pearance of prominent eyes is not directly connected with other 
morphological characters of the transformed amphibians. The larvae 
of Salamandra maculosa which had begun metamorphosis, preserve 
larval respiratory organs when fed on thymus, but their eyes are 
formed like those of terrestrial amphibians. Possibly therefore the 
thymus is able to prevent the influence of one factor caused by the 
thyroid gland (the acceleration of metabolism) but the other factor 
(which causes exophthalmus) appears independently. 
My experiments do not involve any definite conclusion as to 
te above question. In an axolotl fed on the substance extractedh 
from thyroidine tabloids by means of acetone, I observed a pro¬ 
minence of eyes which lasted for a time; but this effect was scarcely 
perceptible and of short duration, so it cannot be considered to 
confirm the hypothesis. The axolotl fed on thyroidine deprived of 
exophthalming substance underwent metamorphosis and had pro¬ 
minent eyes, as in normal terrestrial forms. This result however 
does not negative the hypothesis. From histological investigation it 
follows (see p. 57) that feeding with thyroidine induces changes in 
the structure of the thyreoidea in the animals; the secretion of this 
gland may cause exophthalmus. 
One of the physiological characters of transformed specimens 
are the movements of the throat, to be seen immediately when the 
animals are set on land. In larvae I observed no similar motion, 
