Page:Popular Science Monthly Volume 76.djvu/409

Rh bottom around the corals swims the gray snapper, the commonest predaceous fish of the reefs. Yet these gray snappers are not seen to attempt to devour the reef fishes. Professor Reighard found, however, that when lie captured these beautiful reef fish and threw them in among the gray snappers far from the reefs they were greedily devoured without a moment's hesitation. It became evident that the gray snapper could not capture the brilliant little fishes as long as they enjoyed the protection afforded by the stings of the coral polyps, or remained near the entrances to the intricate caverns of the reefs. Hence these fishes are not warningly colored, and Wallace's hypothesis does not apply to them.

Nevertheless, Professor Reighard found that the gray snapper could distinguish colors, and that it could be taught to associate a brilliant coior with an unpleasant taste.

In order to prove this, he made use of the little silvery sardine (Atherina) which swarms in thousands over the shallows of the reefs, and whose only office in life seems to be to supply food for all larger fishes. Reighard dyed these silvery fish a brilliant carmine red and the gray snappers devoured them without hesitation. Then, however, the tentacles of a medusa were placed in the mouths of the red-colored sardines and the gray snappers soon learned after a brief experience with the stings to avoid them; and they remembered to avoid red-colored sardines after an interval of twenty days had elapsed since they had last seen them, although these later red fish had no medusa tentacles in their mouths. Thus he created a warning coloration; something nature herself had not done.

Professor Reighard's experiments are by far the most convincing that have ever been carried out upon the subject of warning coloration, being performed in surroundings natural to the animals themselves. He concludes that the conspicuous coloration of coral-reef fishes is is not for warning enemies, and is the result of race tendency unchecked by selection.

Another research of interest was that of Dr. Stockard, of the Cornell Medical College, upon the habits of the walking-stick insect, Aplopus, which lives upon the bay cedar (Suriana) bushes at Tortugas and bears an extraordinary resemblance to a stick of the bush itself, while its eggs resemble the seeds of the same bush. Professor Stockard finds that the habits of the insect accord perfectly with and enhance the value of its protective coloration. The insect is active only at night, or in darkness, and in daylight they may be piled one on top of another, remaining motionless as real sticks in any attitude, but if they then be placed in the dark they immediately scramble off in all directions.

In another research Dr. Stockard studied the regeneration of the claws of the snapping-shrimp Alpheus which lives within the cavities