INTEGUMENT OF NECTURUS MACULOSUS 519 
bundles very fine fibers could be seen extending into the outer 
layer, but they never quite reached the lower surface of the 
epidermis. 
CHANGES IN COLORATION 
A. Introduction 
Necturus possesses the ability, common to most Amphibia, 
of changing its color through its control of the black chromato- 
phores. Eycleshymer (’06 a) suspected this, but did not demon- 
strate it. Later (’14), in his work on Necturus larvae, he found 
that twenty-four hours after decapitation the black chromato- 
phores contracted, some partially and others completely. Reese 
(06), Pearse (10), and Sayle (’16) have given accounts of the 
responses of Necturus to light, but they do not make any mention 
of color changes. 
Only the dermal melanophores are concerned in the color 
changes. Those of the epidermis appear not to respond, but 
under any given condition some may be rounded, while others 
are branched. Laurens (15) found that in Amblystoma epi- 
dermal chromatophores are more irregular and variable in their 
responses than the dermal pigment cells. Hooker (14a) did 
not find any correlation in response between the dermal and 
epidermal chromatophores of tadpoles. The xanthophores in 
Necturus, as far as could be ascertained, remain expanded under 
all conditions. 
On account of the great variability in pigmentation, color 
changes are easily overlooked. A densely pigmented animal with 
contracted melanophores is darker than a light colored animal 
with expanded pigment cells, but under the microscope the 
individual cells can be observed, and no mistake as to whether 
they are contracted or expanded is possible. Changes in color, 
due to contraction of the melanophores, become apparent, first 
on the legs, and the venter, if pigmented, will also be found to 
have become much paler. On the sides and dorsal surface of 
the body the changes are not so noticeable. In very dark indi- 
viduals the contraction of the melanophores produces practically 
no change in coloration, but sometimes a gray effect is noted on 
JOURNAL OF MORPHOLOGY. VOL. 34, NO. 3 
