Page:Popular Science Monthly Volume 62.djvu/92

86 fauna of the tide-pools, neglected by almost all collectors. As the tide goes down, especially on rocky capes which project into the sea, myriads of little fishes will remain in the rock-pools, the algæ and the clefts of rock. In regions like California, where the rocks are buried with kelp, blennies will lie in the kelp as quiescent as the branches of the algæ themselves until the flow of water returns.

A sharp, three-tined fork will help in spearing them. The water in pools can be poisoned on the coast of Mexico, with the milky juice of the 'Hava' tree, a tree which yields strychnine. In default of this, pools can be poisoned by chloride of lime, sulphate of copper, or, if small enough, by formaline. Of these, a solution of commercial chloride of lime, yielding free chlorine gas is cheapest and most serviceable. By such means the contents of the pool can be secured and the next tide carries away the poison. The water in pools can be bailed out, or better emptied by a siphon made of small garden hose or rubber tubing. On rocky shores and about coral reefs dynamite can be used to very great advantage, if the collector or his assistant dare risk it, and if the laws of the country do not prevent. Most effective in rockpool work is the help of the small boy. In all lands the collector will do well to take him into his pay and confidence. Of the hundred or more new species of rock-pool fishes lately secured by the writer in Japan, fully two thirds were obtained by the Japanese boys. Equally effective is the 'muchacho' on the coasts of Mexico.

Masses of coral, sponges, tunicates and other porous or hollow organisms often contain small fishes and should be carefully examined. On the coral reefs the breaking up of large masses is often most remunerative. The importance of securing the young of pelagic fishes cannot be too strongly emphasized.

Fishes must be permanently preserved in alcohol. Dried skins are far from satisfactory, except as a choice of difficulties in the case of large species. Dr. Gunther thus describes the process of skinning fishes:

Scaly fishes are skinned thus: with a strong pair of scissors an incision is made along the median line of the abdomen from the foremost part of the throat, passing on one side of the base of the ventral and anal fins, to the root of the caudal fin, the cut being continued upwards to the back of the tail close to the base of the caudal. The skin of one side of the fish is then severed with the scalpel from the underlying muscles to the median line of the back; the bones which support the dorsal and caudal are cut through, so that these fins remain attached to the skin. The removal of the skin of the opposite side is easy. More difficult is the preparation of the head and scapulary region; the two halves of the scapular arch which have been severed from each other by the first incision are pressed towards the right and left, and the spine is severed behind the head, so that now only the head and shoulder bones remain attached to the skin. These parts have to be cleaned from the inside, all soft parts, the branchial and hyoid apparatus, and all smaller bones being cut away