304 CLASSIFIED RESUME OF ORGANISMS OBSERVED 



kinds were produced, one type, by the photophore-like 

 luminous spots characteristic of all euphausids and a few 

 shrimps, and, another, by a discharge of luminous fluid. 

 As is well known, the Hoplophorid Sysiellaspis is capable 

 of producing both kinds, but in most other deep-sea 

 shrimps luminous spots are almost, or completely, lacking. 

 Shrimp-like animals with characteristically arranged light 

 organs were observed several times from 650 feet down- 

 ward; in one case the glow was distinctly greenish. These 

 were unquestionably euphausids. Again, one good-sized 

 shrimp at 1300 feet had six or eight scattered lights, and 

 one long, slit-like light near the center of its body, which 

 identified it with almost complete certainty as Systellaspis 

 debilis. This, with Acanthephyra purpurea, is the com- 

 monest shrimp in our trawling nets. Both euphausids and 

 Systellaspis were observed too briefly to enable me to time 

 the duration of the glow on separate individuals, although 

 in each case it lasted several full seconds — much longer 

 than the momentary flashes the animals give in aquariums 

 on the very rare occasions when they are brought alive to 

 the surface. 



The luminous discharge of large, Acanthephyra-\\\LQ 

 shrimps was a very different sort of illumination. Whereas 

 the photophore-like organs of euphausids may serve chiefly 

 as recognition marks, or other non-defensive capacities, the 

 luminous matter was obviously discharged only when a 

 shrimp was startled, as when it bumped against the bathy- 

 sphere window. When this happened, a rocket-like burst 



