Metamorphosis of, Axolotls 
51 
a larva, with fig. 3, the epithelium of a transformed Amblystoma r 
both magnified to the same extent, shows that in the transformed 
animal the number of epithelial layers is much reduced in comparison 
with the same number in larvae. Its breadth attains here only 70 to 
90 f,i. On the surface a narrow plasmatic layer appears, containing flat, 
long nuclei which become intensely coloured by eosine. Nucler lying 
beneath are also abnormal, low and long with compact chromatine; 
they are stained by haematoxyline. Ley dig’s glands are absent. 
The breadth of the connective tissue is diminished by one-half 
(cf. fig. 1, representing the skin of an axolotl-larva; and fig. 4, 
the skin of a specimen after metamorphosis). The venomous glands 
are transferred almost exactly under epithelium and the ducts on 
the surface of the skin are completely formed. 
No difference in the frequency of blood-vessels in the skin of 
the axolotl and that of Amblystoma was noticed. In both cases the 
vessels lying under the epithelium are numerous (see figs. 1 and 4). 
These vessels become easily seen through the epithelium of a trans¬ 
formed albinotic animal, whose epithelium is thinner than in the 
larva; this transparency causes the pink colour of the skin, already 
mentioned above. Figs. 1 to 4 refer to the skin of albinotic animals; 
in the skin of a transformed black specimen we notice large 
quantities of pigment. Formation of supernormal quantities of 
pigment produced by chemical changes of albuminous substances, 
according to Rûziôka, should be considered a proof of accelerated 
metabolism. 
Decrease in the number of epithelial layers, and formation of 
horny parts on the surface as well as increase in the quantity of 
pigment in the skin of axolotls fed on thyroidine, must be ascribed 
to processes analogous to those which are produced by subjecting 
full-grown animals to starvation. The formation of the first 
moult in the neotenic larvae, fed on extracts of the 
thyroid gland, is due to the same cause as the acceler¬ 
ation of moulting in amphibians subjected to inani¬ 
tion, i. e. the preponderance of disassimilatory over 
assimiTatory processes. 
The lungs. 
The lungs of amphibians are known to develop early; in tadpoles 
they are already containing air. Their rôle however in the inter- 
4 ;* 
