626 
The changes undergone by the tissues are seen in 
the structure of the skin, muscles, and bones. The 
skin is thin, and destitute of bright colors, the shades 
varying from grayish to velvet black (fig. 3). The 
scales, often much reduced in size, are weakly at- 
tached, and the friction which they experience dur- 
ing the ascent of the trawl removes almost all of 
them. The muscles have little resistance, and, being 
without flavor, the fish are not edible. ‘The bones are 
friable, and spongy inside. 
In fishes living continuously at a depth to which 
a little light penetrates, the eyes are quite large in 
SCIENCE. 
[Vou. III., No. 68 
ofafisherman. This fact has been verified, long since, 
in the case of surface fishes which hunt at night. 
Thus Bennett describes a species of shark remarka- 
ble for a bright green phosphorescence, which is 
emitted from the whole lower portion of its body. 
This learned zodlogist one day brought one of these 
fishes into a dark room, which was immediately illu- 
minated by its body. The light is increased neither by 
motion nor by rubbing. After the shark’s death, the 
light from the stomach first disappeared. The jaws 
and the fins were the last to retain the phospho- 
rescence. The various sharks found only at a depth 
Kic. 3.— EUSTOMIAS OBSCURUS. 
order to present a larger sensitive surface. This fact 
recalls what we notice in crepuscular birds, whose 
visual organs are also much developed. Among fishes 
at a great depth, this increase of the size of the eye 
is not observed. These organs are of normal size, 
and possess nothing peculiar, either in their position 
or structure. Their function in absolute darkness 
seems at first almost incomprehensible. When, how- 
ever, one recognizes the fact that these animals pos- 
sess phosphorescent plates, or, rather, that they are 
covered by a luminous mucous coating capable of 
lighting a considerable space, the explanation is 
found. This phosphorescence serves partly to guide 
them, and partly to attract prey. It serves, in the 
latter case, the same purpose as a torch in the hand 
of two thousand metres, of which several specimens 
were taken by the Talisman off the coast of Portu- 
gal, must, like the fish of which Bennett spoke, use 
the light which they emit to attract the fishes on 
which they feed. What is the origin of this mucous 
coating, which is thus able to shed so bright light ? 
It must be due to the existence of glandular organs, 
scattered along the sides and the tail, near the eyes 
on the head, and sometimes more sparsely on the 
back. But, besides these glandular follicles, certain 
fishes have apparatus of a quite different kind, which 
emits light. These organs consist of a sort of bicon- 
vex transparent lens, closing externally a chamber 
filled with transparent liquid. This chamber is fur- 
nished with a membrane of black color, formed of 
