454 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 60 



lyfishes, siphonopliores, comb-jellies (pi. 3, fig. 1), tunicates (pi. 4, 

 fig. 1), etc., which flash brightly when they are mechanically stimu- 

 lated. These creatures, of course, have their specialized enemies, but, 

 by and large, they are left alone by large active swimmers. The light 

 they produce outlines the entire body and so gives any creature 

 bumping into them in the dark a chance to recognize them and steer 

 clear. A somewhat similar function is served by the luminescence 

 of sedentary animals on the bottom such as hydroids and sea pens. 

 They flash or twinkle all over when touched, and thus warn would-be 

 settlers that the territory is already occuj)ied. 



Some lummous animals, such as the paddleworm Chaetopterus (pi. 

 3, fig. 2) , live in tubes, or burrows, and discharge a luminous secre- 

 tion when disturbed. Intruders seeking dark crannies in which to 

 lodge or deposit their eggs are thus w^arned that the owner is at 

 home, and the luminescent light makes the place less attractive to an 

 intruder. Polynoids or scale worms appear to use their light as a 

 "sacrifice-lure." These worms have luminescent scales on the back; 

 they cast them off if they are disturbed, and the scales continue flash- 

 ing while the worm crawls away. A variation on this theme is en- 

 countered among deep-sea prawn and fish which discharge a luminous 

 cloud when attacked. The flash of light momentarily blinds or dis- 

 tracts an attacker, while the producer beats a hasty retreat. 



Some fish appear to use their lanterns for illuminating their sur- 

 roundings when feeding or hunting. This is probably the function 

 of the large light organs which lie underneath the eyes of fish such 

 as Anomalofs and Stomias. Many deep-sea fish possess luminous 

 fishing lures on barbels or tentacles, which are displayed so as to at- 

 tract prey within reach of their gaping jaws, for example, stomiatoids 

 and ceratioids or angler-fishes. Others have batteries of light organs 

 tliat serve the same purpose within their mouths and throats; e.g., 

 GhauUodus. 



Some marine animals live and migrate together in dense schools, 

 and luminescence certainly plays a role in enabling the members of 

 the school to keep together in the ocean depths. The firefly squid of 

 Japan, Watasenia scintillans, which comes to the surface annually in 

 large swarms, is an example. The flashing photophores which deck 

 the arms and bodies of these squid keep the school together. Schools 

 of flashing hatchetfish (pi. 2, fig. 1) and lantern fish were seen by 

 Beebe during his deep-sea descents. Euphausiids are another group 

 of luminous marine animals tliat occur in vast schools. These animals 

 make vertical migratioiis toward the surface each evening, and are 

 believed to be one of the agents responsible for the deep-scattering 

 layers recorded on echo sounders. Euphausiids bear batteries of 

 photophores which enable them to signal to one another, and from the 



