The spines of the first back-fin and of the gill-cover are highly poisonous.
Passing over one or two unimportant groups, we come to the family of the Frog-fishes, which, but for the fact that many of its members are poisonous, calls for no special comment here. One species, however, from the coasts of Central America, possesses the distinction of having the most highly developed poison-organs of any fishes, being equalled only by the Venomous Snakes. The poison-weapons are a spine on the gill-cover and two spines of the back-fin. The former is of the same shape as the hollow venom-fang of a snake, perforated at both ends. A little bag containing the poison lies at the base of the spine, and when pressed by the spine as it makes its puncture ejects its contents into the body of the latter, whence it escapes from the hole in the top. The structure of the back-spines is similar.
Photo by Reinhold Thiele & Co.] [Chancery Lane, W.C.
ANGLER-FISH.
This hideous species is also called the Frog-fish.
The family of the Angler-fishes contain more strange forms than any other. Living on the sea-bottom and seeking their prey by stealth, angler-fishes do not need powerful swimming-muscles; consequently the size of the body and tail has become considerably reduced, so that the head, relatively to the rest of the body, is unusually large. The head, jaws, and belly are indeed of great size and capacity. The side or paired fins are not used for swimming, but have become modified to serve as feet, enabling the fish to shuffle along the ground. A further remarkable feature of these fishes is seen in the back-fin, the rays of which are very long, the foremost being provided with a flag-like flap of skin at the top, extremely sensitive to touch, and playing a very important part in the capture of food. It seems that the fish commonly lies concealed on the sea-bottom, with this "flag" erected. From its general resemblance to the surrounding seaweed it is quite inconspicuous, so that passing fishes take no trouble to avoid it. If by any chance they should touch it, however, the jaws beneath open instantly, and the unfortunate trespasser is suddenly engulfed. This elaborate and sensitive mechanism has been likened to a spring-trap, which is always set, and never betrays its presence. It seems probable, however, that this flag serves also as a lure, passing fishes being occasionally attracted by the waving flap of skin. Should they become sufficiently curious as to proceed to touch it, capture in the manner above described is certain. Certain deep-sea forms have a luminous organ in the place of the flap of skin, and this certainly seems to act only as a lure.
Angler-fishes are found all over the world; some, as we have seen, are bottom-fishes, some inhabit deep sea, whilst others lie hidden amongst floating seaweed, to which they cling by means of their arm-like fins. Only one species occurs in British waters. Its method of spawning is remarkable, in that the eggs are laid in the form of large raft-like sheets, which float on the surface of the sea. The number of eggs laid by a single fish has been computed to be 1,345,000. A single sheet of spawn may measure from 2 to 3 feet in breadth and from 25 to 30 feet long.
Photo by by W. Saville-Kent, F.Z.S.] [Milford-on-Sea.