Significance of Conspiciiousncss in Coral-Rcef Fislirs. 309 



rather than for holding active prey. The only records of examinations of 

 stomach contents known to the writer are embodied in table 15. This includes 

 18 species represented by at least 108 individuals and shows the food to in- 

 clude the following fixed or very slow-moving forms: Algre, ascidians. bryo- 

 zoa, sea-urchins, gorgonians, mollusks, sponges. The annelids are in one 

 case sedentary or tube-inhabiting forms and are possibly so in all cases. Of 

 active forms, Crustacea are mentioned but four times and ophiurians once ; 

 both mav have been taken after death. The sand is probably adventitious 

 and the foraminifera may have been included in it. The conclusion seems 

 to be warranted that the food of these coral-reef fishes consists of in- 

 vertebrates, the bulk of it of fixed forms. There appears to be no evidence 

 that any of these aquatic invertebrates discriminate colors (Washburn, 1908, 

 Chapter VII). Aggressive color-resemblance can then afford no advan- 

 tage to fish approaching such prey and selection could not have operated 

 through the food to hold in check the development of their brilliant colors. 



Protective resemblance seems to have been equally unnecessary for the 

 conspicuous coral-reef fishes. Protected by their agility and their nearness 

 to the coral-rock labyrinths, they readily elude their enemies. The method 

 of escape and subsequent behavior of small Abudefduf marginaius and of 

 Elacatinns related on p. 302 show that these fish are immune from attack 

 when near a large flat surface, whether that surface is or is not clothed 

 with coral polyps. That the conspicuous coral-reef fishes are pursued and 

 captured by the gray snapper when they venture away from the reefs is 

 shown bv the feeding experiments already described. One of the fish thus 

 instantly devoured by the snappers was a young Anisotremus virginiais, 

 or porkfish, yet I have twice seen this conspicuous fish emerge from crev- 

 ices in the coral rock and go to a distance of 6 to 8 inches to nibi)le at 

 the surface of a gray snapper. It avoided the head of the snap|)er and 

 appeared to be seeking food in the region of the anal opening. Instead of 

 attempting to seize it the snapper lowered the dorsal, wriggled as though 

 annoyed, and then swam away. The instance illustrates the immunity en- 

 joyed by such fish when on the reefs and the recognition by the snapper of 

 their inaccessibility under these circumstances. The gray snappers were 

 never seen to attempt to pursue the conspicuous fish into the recesses of the 

 coral reefs. In the gloom prevailing there the colors of the fish would be 

 indistinguishable and could not then, even sliould we assume them to be 

 associated with disagreeable (|ualities, serve to warn their foes. Protective 

 resemblance is unnecessary for such fishes. For them coloration has no 

 selective value. Even were they protectively colored the sharp sight and fine 

 power of discrimination of the snappers would probably enable them to cap- 

 ture the fish at a distance from the reefs, but it is only when they reach a size 

 which renders them immune from attack that they venture to a distance. 

 Since these fishes, if removed from the reefs, would, on account of their 



