THE DORAB 2859 



organs are covered with a coating of lumious mucus, or bear phosphorescent plates. 

 The phosphorescence with which the fishes of the ocean depths are endowed serves 

 indeed both to guide them and to attract their prey, filling for them in the latter 

 case the same office as a torch in the hand of a fisherman. This peculiarity has 

 been long noticed in surface fishes which pursue their prey at night; Bennet, for 

 instance, having described a shark which gives off a bright green phosphorescence 

 from the lower surface of its body. On one occasion that zoologist brought into a 

 room a freshly-caught specimen of this shark, upon which the whole chamber was 

 illuminated with the light given off from its body. It is probable that the different 

 species of sharks living at moderate depths, like the one described by Bennet, make 

 use of their luminosity solely for the purpose of attracting their prey within reach. 

 In most cases the origin of this light-giving mucus must be attributed to glandular 

 organs distributed along the flanks and tail, on the head, and more rarely on the 

 back. There exists, however, in certain fishes, which lack these glandular organs, 

 an apparatus of a totally different nature for the emission of light; this apparatus 

 consisting of a kind of biconvex transparent lens closing the front of a chamber 

 filled with clear fluid. This cavity is carpeted by a blackish membrane, formed of 

 hexagonal cells, thus recalling the retina of the eye, and is connected with certain 

 nerves. Phosphorescent plates of this type may be situated either beneath the 

 eyes, or on the sides of the body," one of the fishes thus furnished belonging to the 

 family now under consideration, in which it forms the genus Malacosteus. A 

 specimen of this fish captured before death had ensued was observed to emit a 

 yellowish light from the uppermost plate beneath the eye, while that from the 

 lower plate had a greenish tinge. In the genus Stomias, continues our author, 

 " the sides of the body present a double longitudinal series of phosphorescent plates, 

 which emit light in such a manner as to cause the whole fish to be bathed in a 

 brilliant luminous halo. This fish must, indeed, be a formidable creature to the 

 other inhabitants of the ocean abysses; being in every way constructed and armed 

 for strife, and its powerful teeth admirably fitted to seize and tear the flesh of the 

 other fishes upon which it preys." In other species (e.g. Eustomias) the barbel is 

 greatly lengthened, all the fins form long dentated filaments; the whole of these 

 structures being apparently modified for the emission of phosphorescent light. In 

 our figured species not only are there luminous dots down the sides of the body, 

 but also larger plates beneath the eyes. 



THE DORAB Family CHIROCENTRID^ 



With the fish represented in the illustration on p. 2860, which ranges from 

 the Red Sea to the Malay Archipelago, and is commonly known in the East as the 

 dorab (Chirocentrus dorab), we come to the first of what we may term the herring 

 and salmon group, the more typical members of which differ from the preceding 

 families of this section in having the parietal bones of the skull separated from one 

 another by the intervention of the supraoccipital. In common with the herrings, 

 this fish, which is the sole representative of its family, has but a single true tail 



