New York, September 22, 1915. No. 22 



OFEl 



Published to advance the Science of cold-blooded vertebrates 



A PECULIAR COLOR DISPLAY IN THE 

 YELLOW GRUNT. 



While at the Marine Biological Station of the 

 Carnegie Institution at the Tortugas Islands in the 

 Gnlf of Mexico, I had many opportunities to ob- 

 serve the brilliant colors of the coral-reef fishes. 

 These are seen at their best only when the fish are 

 at liberty in their natural waters. 



The yellow grunt, Hacmulon sciurus, has the 

 head and body broadly striped with chrome-yellow 

 and lavendar-blue. The anals and ventrals are yel- 

 low, the belly and throat white. The outside of the 

 fish would seem to afford a sufficient display; but, as 

 in other grunts, the interior of the mouth is bright- 

 colored. In this species it is vermilion everywhere 

 from the caudal margin of the breathing valves as 

 far back as the first gill slit. The mouth is large and 

 can be opened very wide. When so opened it ap- 

 pears as a conspicuous red patch. 



One morning in July, 1905, I crushed a large 

 black sea-urchin (Diadema) and threw it into the wa- 

 ter. Two yellow grunts soon appeared and began to 

 feed on it. When I first saw them they were about a 

 foot apart and directly facing each other. Presently 

 one of them opened its mouth very wide so as to dis- 

 play fully its red lining. He then swam toward the 

 other. The second fish opened its mouth in the same 

 way but did not move. The first kept on until the 



