4i2 FISHES 



which occur at moderate depths, others at very great depths, 

 and many of which do not possess luminous organs. For in- 

 stance, in the whole family Synodontidae there are no such 

 organs. One of these named Benthosaurus was taken by the 

 Challenger off the coast of New Zealand at a depth of i ioo 

 fathoms, other specimens were taken by the American exploring 

 vessel Albatross at similar depths. Another species of the same 

 genus was taken by the Challenger at the enormous depth of 

 2385 fathoms in the South Pacific. On the other hand, Harpo- 

 don nehereus belonging to the same family is caught in great 

 numbers for food in the estuary of the Ganges, and in the dried 

 state is well known to Anglo-Indians as Bombay duck. It 

 is stated to be brilliantly phosphorescent all over the body 

 when first caught, but it has no special luminous organs. It is 

 possible, as Dr. Giinther says, that this fish usually lives at 

 some considerable depth and only comes into shallow water 

 temporarily, perhaps to spawn, for it has the sensory canals of 

 the lateral line and head much enlarged as in most deep-water 

 fishes. Another allied family, that of the Chlorophthalmidai, 

 which means green-eyed fishes, is also without luminous organs. 

 Bathypterois, a member of this family, occurs off the coast of 

 Brazil at 500 to 700 fathoms ; it has the upper rays of the pec- 

 toral fins prolonged to a length nearly equal to that of the body 

 and evidently serving as tactile filaments whose sensitiveness 

 compensates for the small size of the eyes. 



Perhaps the most extraordinary of all abyssal fishes is one 

 called Ipnops. Placed by some ichthyologists among the 

 Chlorophthalmidne, by others in a family by itself, it is in all 

 probability a truly abyssal fish. It was originally discovered 

 by the Challenger, four specimens having been taken off the 

 coast of Brazil and to the north of Celebes at depths varying 

 from 1600 to 2150 fathoms. In this fish there are no small 

 light-organs like those of Myctophum, but the head is flattened 

 and the whole of its upper surface is occupied by a pair of 

 peculiar organs believed to be phosphorescent, while eyes are 

 entirely absent, and apparently the olfactory organs also. ( Plate 

 XXXI., D.) These organs in the preserved fish have the whitish, 

 opaque appearance which is characteristic of luminous organs 

 generally, but the actual emission of light from them has never 

 been observed, the specimens taken being always dead by the 



