THE TRUE FISHES. 189 
the bottom, lying upon its left’ side, the eye moving over, 
the successive stages of the movement being shown in 
Fig. 231, until both eyes are upon the right side, which 
is now the upper portion. The mouth is generally twist- 
ed to conform with the new position. On the lower 
side the pigment-cells are not developed, and the skin is 
white, but the upper surface is colored and susceptible 
to change and adaptation to the prevailing color of the 
bottom. 
Note.—This protection, afforded many animals, is due to the. con-- 
traction and expansion of the different colored pigment-cells that arc 
contained principally in the cutis. They contract or expand according 
to the light reflected ; the impression is received by the eye and trans- 
mitted by the sympathetic nerves. A blind flounder does not adapt 
its color to the surroundings. By severing some of the nerves Pou- 
chet produced, at pleasure, a fish striped on one side and. spotted on 
the other, etc. The experiment may easily be tried by placing floun- 
ders on white, brown, and black bottoms, and changing them about ; 
so also with the octopus, anolis, and many others. 
Order VI. Pediculati. Walking-Fishes (Axzen- 
nartide).—These are pelagic fishes, floating about upon 
the surface of the sea among the vast fields of sargassurn. 
The body is compressed, and three or four inches long ; 
the fins ornamented with barbels, so that they can be 
scarcely distinguished from the weed, which they also 
mimic in-color. They are interesting nest-builders (Fig. 
232), collecting the floating weed into balls as large’ as 
a cheese, connecting it by bands of a glutinous secretion 
probably taken from a special gland, as in the stickle- 
backs (Fig. 206). The eggs are attached on the sides 
and within, Allied are the anglers (Lophitde) (Fig. 233), 
so called from several spines on the head that have 
upon their ends barbels of flesh. The spines move up 
and down over the enormous mouth like a fishing-rod ; 
the waving bait attracting the smaller fishes, that often 
fall victims to the curious fisherman. Some of this fam- 
