330 Papers from the Marine Biological Laboratory at Tortuyas. 



XI. SUMMARY. 



This paper embodies a search for the biological significance of the con- 

 spicuousness which it attempts to show characterizes many of the coral-reef 

 fish of the Tortugas region. After showing that this conspicuousness is not 

 a secondary sexual character and that it serves neither for protective or 

 aggressive resemblance its value as a warning character is subjected to 

 experimental test. 



E.xperimental evidence is presented to show that the gray snapper, the 

 commonest predaceous fish of the region, discriminates certain colors, forms 

 associations with great rapidity, and retains these associations for a consid- 

 erable time (memory). If any of the coral-reef fishes possess a combina- 

 tion of conspicuousness with such unpleasant attributes as render them 

 unpalatable, the gray snapper should have learned to avoid them at sight and 

 their conspicuousness would then have a warning significance. It is shown 

 that when atherina, an inconspicuous fish which serves normally as the food 

 of the gray snapper, is given an artificial warning color and at the same time 

 rendered unpalatable, it is, after a brief experience, no longer taken as food 

 by the gray snapper. Artificially colored atherinas thus come to have a 

 warning significance for the gray snapper and are avoided, even when not 

 unpalatable, although normal atherinas are still readily eaten. The conclu- 

 sion is thus reached that the existence of a warning coloration or of warning 

 conspicuousness in coral fishes is easily possible. 



This possibility was tested by feeding to gray snappers in their natural 

 environment but at a distance from the reefs, conspicuous coral-reef fishes 

 both living and dead. Of the 21 species thus fed all were taken by the gray 

 snapper, with the exception of one which escaped by reason of the large size 

 of the individual used. It is concluded that these coral-reef fishes do not 

 possess that combination of conspicuousness with unpleasant attributes neces- 

 sarv to the theory of warning coloration. Their conspicuousness has no 

 warning significance. Certain further evidence is presented to show that the 

 rapidity and nicety of adjustment of the gray snapper to its food is such that 

 it learns to avoid what is unpalatable without the necessity of its being warn- 

 ingly colored or otherwise conspicuous. 



The conclusion is reached that the conspicuousness of coral-reef fishes, 

 since it is not a secondary sexual character and has no necessary meaning 

 for protection, aggression, or as warning, is without biological significance. 

 The coral-reef fishes have no need of aggressive inconspicuousness because 

 their food consists of invertebrates, chiefly fixed. They have no need of 

 protective inconspicuousness because the reefs and their agility afi^ord them 

 abundant protection. Selection has therefore not acted on their colors or 

 other conspicuous characters, but these have developed in the absence of 

 selection and through internal forces. They are the result of race tendency 

 unchecked bv selection. 



