134 ANOTHER VISIT TO THE ANDAMANS 



across phosphorescent zoophytes, and jelly-fishes, and 

 sea-worms, and starfishes, and all who have made a 

 long sea-voyage have seen the brilliant coruscations 

 of the oceanic Tunicates {Pyrosoma and Salpd), and 

 know of the scintillations emitted by certain nocturnal 

 fishes. 



With regard to several of the luminous fishes, the 

 actual mechanism by which the light is produced and 

 radiated has been described, and it is also known that, 

 in some instances, the luminous emissions are under 

 the animal's control. Among these fishes we find 

 every gradation of luminous organs, from a simple 

 dazzling patch of skin, encircled by a ring of absorbent 

 black pigment, to prevent diffusion, up to an elaborate 

 glandular structure, provided with reflecting and con- 

 densing apparatus, very much like a bull's-eye lantern. 



Our knowledge, however, of the sources of the 

 light emitted by the higher Crustacea is still very 

 incomplete. On the occasion of which I am now 

 writing three large species of luminous deep-sea crus- 

 taceans were brought on board alive, namely, Hetero- 

 carpus alphonsi, Aristceus cortiscans, and Pentacheles 

 phosphorus. Far the most brilliant of them was 

 Heterocarpus alphonsi, both sexes of which poured 

 out, apparently from the orifices of the ''green glands" 

 at the base of the antennae, copious clouds of a ghostly 

 blue light of sufficient intensity to illuminate a bucket 

 of seawater so that all its contents were visible in the 



