peared.

Sir Wyville Thomson mentions a kind of Crab (Ethusa granulata), which
when living near the surface has well developed eyes; in deeper water,
100 to 400 fathoms, eyestalks are present, but the animal is apparently
blind, the eyes themselves being absent; while in specimens from a depth
of 500-700 fathoms the eyestalks themselves have lost their special
character, and have become fixed, their terminations being combined into
a strong, pointed beak.

In other deep sea creatures, on the contrary, the eyes gradually become
more and more developed, so that while in some species the eyes
gradually dwindle, in others they become unusually large.

Many of the latter species may be said to be a light to themselves,
being provided with a larger or smaller number of curious luminous
organs. The deep sea fish are either silvery, pink, or in many cases
black, sometimes relieved with scarlet, and when the luminous organs
flash out must present a very remarkable appearance.

We have still much to learn as to the structure and functions of these
organs, but there are cases in which their use can be surmised with some
probability. The light is evidently under the will of the fish.[61] It
is easy to imagine a Photichthys (Light Fish) swimming in the black
depths of the Ocean, suddenly flashing out light from its luminous
organs, and thus bringing into view any prey which may be near; while,
if danger is disclosed, the light is again at once extinguished. It may
be observed that the largest of these organs is in this species situated
just under the eye, so that the fish is actually provided with a bull's
eye lantern. In other cases the light may rather serve as a defence,
some having, as, for instance, in the genus Scopelus, a pair of large
ones in the tail, so that "a strong ray of light shot forth from the
stern-chaser may dazzle and frighten an enemy."

In other cases they appear to serve as lures. The "Sea-devil" or
"Angler" of our coasts has on its head three long, very flexible,
reddish filaments, while all round its head are fringed appendages,
closely resembling fronds of sea-weed. The fish conceals itself at the
bottom, in the sand or among sea-weed, and dangles the long filaments in
front of its mouth. Little fishes, taking these filaments for worms,
unsuspectingly approach, and thus fall victims.

Several species of the same family live at great depths, and have very
similar habits. A mere red filament would be in