INTEGUMENT OF NECTURUS MACULOSUS 499 
2. Molting. Kneeland (’57) states that Necturus sheds its 
epidermis in the winter. Eycleshymer (’06 a) reports, from notes 
made by one of his students on February 9, 1897, as follows: 
“The epidermis as a thin layer appeared to have loosened from 
the entire surface of the body, appearing frosty-white with 
bubbles of air. The loosened epidermis was split along the mid- 
dorsal line, its free edges floating upward in ragged streamers. 
‘On the following day none of the epidermis remained excepting 
glove-like portions which were yet attached to the feet; these 
portions were not cast until two days later.” Reese (’05) finds 
that Cryptobranchus, when kept in captivity, sheds a ‘thin 
transparent cuticle.’ ; 
I have invariably found that animals which have been sub- 
jected to trying conditions in the laboratory cast a thin layer 
of epidermis soon after. Mr. Cole’s description, quoted by 
Eycleshymer (’06 a), is an accurate account of the process, but 
the time of the year, under laboratory conditions at least, does 
not appear to have anything to do with the act, since molting 
can be induced in the same animal several times in close succes- 
sion by removing it from the water and allowing it to dry in the 
air for a short time. Only the cells bearing the cuticular margin 
are cast. Sections prepared from portions shed show the lower 
edge of the cuticular layer to be irregular, with the bases of the 
cells at higher and lower levels as they were when in position 
on the animal. Preparatory to molting, therefore, there is no 
flattening or other change in the form of the cells of the outer 
layer nor any differentiation of the outer surfaces of the under- 
lying cells such as has been described by Schuberg (’91 a) for 
the tree-frog. 
C. Horny layer 
An actual horny layer, such as is described for land-inhabiting 
Amphibia, is found only on the hands and feet of Necturus. All 
of the outer cells over the rest of the body bear on their edges 
the cuticular margin, typical of all permanently aquatic Amphibia 
and of the water-inhabiting stages of the terrestrial forms. The 
cornification involves several layers.and the cells are much 
