Significance of Coiispicuousiicss in Coral-Rccf Fishes. 307 



once taken. It also is inconspicuous. Medusae and Ctenophores of vari- 

 ous sorts, usually inconspicuous, are not eaten. 



We may say by way of summary that the gray snapper discriminates 

 with great rapidity and delicacy betzveen the various possible-food elements 

 of its environment, which are not conspicuously different from each other. 



X. GENERAL DISCUSSION OF CONSPICUOUSNESS IN ANIMALS. 



THE SIGNIFICANCE OF CONSPICUOUS COLORATION IN CORAL-REEF FISHES. 



If the foregoing account is correct the gray snappers, the commonest 

 predaceous fish of the coral reefs, possess all the qualities required by the 

 theory of warning coloration. They distinguish colors, form associations 

 with great readiness, and retain these associations for a considerable time. 

 Presumably other predaceous fish of the region do the like. By these 

 qualities the snappers adjust themselves continually to their environment. 

 Their capacity for behavior adjustment is indeed so great that a familiar 

 disagreeable quality added to their wonted food is enough to render that 

 food immune from their attacks, and this happens after approximately a 

 single experience of taking the food into the mouth (experiment 32, p. 285). 

 An adjustment even more rapid takes place toward food of unfamiliar ap- 

 pearance, but with well-known unpalatable qualities (atherina-shaped colored 

 cassiopea pieces, experiment 34, p. 305). Their capacity for adjustment is 

 such that the snappers have learned all the food possibilities of the environ- 

 ment — what is good for them to eat and what is not. They refuse at sight 

 jelly-fish and brittle-stars, and in spite of the fact that these forms are very 

 inconspicuous, they distinguish them as not good to eat. A warning colora- 

 tion is quite unnecessary for the protection of these unpalatable forms 

 There can be no doubt that if any animal in the environment of the snappers, 

 whether conspicuous or inconspicuous, should develop highly disagreeable 

 qualities, it would, after a brief experience, be unmolested by them. 



When, under quite normal conditions, the gray snappers were given an 

 opportunity to feed on conspicuously colored coral-reef fishes of suitable 

 size they took without hesitation all the species offered them. Most of these 

 22 species are highly conspicuous fish ; several have both conspicuousness 

 and formidable means of defense. That they are greedily taken by the gray 

 snappers and that the fish themselves make every effort to escape are facts 

 which seem to admit of no other interpretation than that their conspicuous- 

 ness has no warning significance. We must, then, seek some other meaning 

 of the conspicuousness of these fish. Reasons have been already given (p. 

 263) for the belief that we are not dealing here with sexual selection. 



That the conspicuous coral-reef fish are not instances of aggressive re- 

 semblance either general or special is evidenced by their conspicuousness, 

 as shown in the photographs (plates i to 5, except plate 4, fig. 9). That an 

 aggressive resemblance (enabling them to approach their prey) is unneces- 



