n6 PAPERS FROM TORTUGAS LABORATORY vol. xxxiv 



colony of this snapper was fed with fish and crustaceans, which were marked by 

 drawing a black thread through them. This marked food was offered between 2 -.2^ 

 and 2:35 p.m., and 5 of the fish were killed with dynamite 2 l / 4 hours after the 

 feeding. The stomachs contained the marked food listed: Monacanthus sp., 4 

 specimens, 45 to 63 mm. long; Scants croicensis, 2, 35 and 40 mm. long; Hali- 

 choeres bivittatus, 4, 50 to 63 mm. long; Haemulon sciitrits, 2, 45 and 55 mm. 

 long; Malacoctenus macropus, 1, 32 mm. long; Mithrax hispid us, 3, 11 mm. 

 across carapace; and Portunus sp., 1, 21 mm. across carapace. Digestion had pro- 

 ceeded far enough in the fishes to destroy the color pattern, and in most instances 

 to erode the abdominal walls. The crabs, however, remained virtually unchanged. 



In a similar experiment 26 snappers were killed 3V2 hours after feeding. The 

 stomachs, however, were not examined until an hour later. Only 5 of the fish 

 contained marked food, consisting of the species listed as follows: }enhjnsina 

 lamprotaenia, 5 specimens, 2 reduced to fragments, 3, 40 to 50 mm. long; Hali- 

 choeres bivittatus, 6, 37 to 82 mm. long; Pomacentrus sp., 1, 55 mm. long; Poma- 

 centrus leucostictus , 1, 55 mm. long; Monacanthus sp., 1 fragment, and 1, 30 mm. 

 long; Malacoctenus macropus, 2, 30 and 33 mm. long; Harengula sardina, 1, 55 

 mm. long; Syngnathus sp., a fragment; Sphoeroides spengleri, 1, 50 mm. long; 

 Haemulon sciurus, 1, 40 mm. long; Sphyraena barracuda, 1, 50 mm. long; 

 Sparisoma sp., 1, 82 mm. long; Portunus sp., 1, 20 mm. across carapace; Mithrax 

 sp., 1, 12 mm. across carapace; Mithrax hispidus, 3, 13 to 22 mm. across carapace; 

 and a shrimp fragment. As already indicated, some of the food had been reduced 

 to fragments, and in all the species of fish the bodies had more or less disinte- 

 grated, but in the crabs digestion had scarcely begun. 



Sometimes at the Laboratory wharf the snapper colony exhibited the species' 

 power of adaptive color change. Usually the fish there were in an intermediate 

 gray phase, with or without an oblique dark line through the eye. Toward eve- 

 ning, however, over clear white sand I have seen them very pale, but over 

 adjacent bottom covered with dark brown, dead turtle grass and algae they 

 invariably and almost immediately turned quite dark. Along the beach rock, in 

 the brown zone between the intertidal strip and stirred sand, I found gray 

 snappers browner than in the other two places. Close beside or beneath Orbicella 

 heads or in the thickets of Acropora they sometimes appeared in a blotched 

 pattern, in which on a dark background there were light gray spots on the back 

 at the base of the dorsal fin. About a shoal cutting off a lateral pocket from the 

 upper blue hole inside Bird Key reef they sometimes floated high in ghostly gray; 

 toward the eastern side of the main Loggerhead bank, in deep water, I have seen 

 them high up, floating by hundreds in the same gray without even showing the 

 ocular stripe. W. H. L. 



Dr. Longley reported some interesting observations in his article entitled "Life 

 on a coral reef" (Nat. Geog. Mag., vol. 51, 1927, pp. 61-83, w i tn &g s -)> showing 

 that this snapper and the schoolmaster (and presumably others) mostly idle the 

 days away in schools on the reefs, but when dusk comes the schools break up and 

 the search for food begins. Dr. Longley also gave some interesting facts about the 



