302 Papers from the Marine Biological Laboratory at Tortugas. 



The 3 individuals which escaped joined others of their species which 

 had been for some days living apparently unmolested against the flat bottom 

 and sides of a large, floating live-box. This little group of perhaps a dozen 

 small Abudcfduf was within a few feet of lOO or more voracious snap- 

 pers. They were never seen to go more than a foot or two from the surface 

 of the box when feeding. When approached they retreated close to the box, 

 which was smooth on the outside and had no crannies in which they 

 could find shelter. The snappers were never seen to attempt the diticult 

 task of capturing one of these agile little fish against the smooth, hard sur- 

 face of the box. Not their coloration, but nearness to a large, hard sur- 

 face protected them. 



(5) Was nearly dead when thrown and was at once taken. The remain- 

 ing 6 Abudefduf were made immobile by cutting the spinal cord. 



(6) and (7) Thrown in the usual way. They were not at first noticed, 

 but as they sank and made no effort to escape, they were seized. 



(8) (9) (10) and (11) Offered to the snappers in the following man- 

 ner: Bread crumbs were thrown to the living Abudefduf at the side of the 

 live-box. They fed on these at and near the surface, but did not venture 

 to follow them as they sank. Beneath the Abudefduf the snappers assembled 

 to feed on the sinking bread crumbs. The immobile Abudefduf were 

 dropped one at a time past the edge of the live-box, so that they fell among 

 the living ones, which were only 2 or 3 feet above the snappers. As the 

 first immobile (No. 8) Abudefduf sank it was followed for a foot or so 

 by one or two living individuals. The snappers gave no heed to either. 

 The living fish returned to the surface, the motionless one sank, still un- 

 heeded, among the snappers. When it had reached the bottom and lain 

 there for a moment it was quickly seized. (9) (10) (11) were thrown 

 in precisely the same way as (8), and with the same result. 



Clearly the Abudefduf near the live-box are treated by the snappers 

 as inaccessible, while individuals of the same species at a distance from 

 the live-box are eagerly pursued and often captured. Immobile Abudefduf 

 that sink from the live-box group among the snappers are taken only after 

 a short time, time enough to bring to the snappers a perception of their 

 distinctness from the immune live-box group. 



(e) Elacatinus oceanops. This slender fish, 1.5 to 4 inches long, is found 

 on the surfaces of the massive coral (Orbicella), close pressed to the living 

 polyps. I have found it fully exposed, not " endeavoring to shelter itself in 

 bottom of grooves," as stated by Jordan and Thompson (1905). In this 

 position, where it is conspicuous by reason of its strongly contrasted stripes, 

 it is shown in plate 4, fig. 8. When dislodged it takes a zigzag course 

 to a new resting-place, as described by Jordan (1904). With the greatest 

 difficulty it may be captured from the coral with a hand net. 



Two individuals were thrown from the dock to the snappers. The first 

 was pursued, but went at once toward a spile beneath the dock. It was 

 lost to view, but later found clinging to the spile. A second individual 

 thrown in further from the dock was at once snapped up. Here, as in the 

 case of Abudefduf, coloration appears to be no protection, but erratic move- 

 ment aids escape, and nearness to a large, hard surface affords protection, 

 more effective, perhaps, in the case of Elaeatinns, because of the nettle-cells 

 of the coral polyp to which the fish clings. 



The case of Leptechineis naucrates is of interest in connection with that 



