THE TORTUGAS LABORATORY 405 



bottom around the corals swims the gray snapper, the commonest pre- 

 daceous fish of the reefs. Yet these gray snappers are not seen to 

 attempt to devour the reef fishes. Professor Reighard found, how- 

 ever, that when lie captured these beautiful reef fish and threw them in 

 among the gray snappers far from the reefs they were greedily de- 

 voured 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 bril- 

 liant 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-col- 

 ored sardines after an interval of twenty days had elapsed since they 

 had last seen them, although these later red fish had no medusa ten- 

 tacles in their mouths. Thus he created a warning coloration ; some- 

 thing 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 dark- 

 ness, and in daylight they may be piled one on top of another, remain- 

 ing 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 



