298 GEOGRAPHICAL AND GEOLOGICAL DISTRIBUTION. 



their habits, living in a deeper zone during the day, and appearing 

 at the surface only at night. The majority of these are provided 

 with phosphorescent organs, a structure largely prevalent among 

 deep-sea fishes, to which these fishes effect a passage. 



Deep-Sea Fishes. Much uncertainty still remains as to the 

 character of the abyssal ichthyic fauna, owing to the difficulty of 

 determining in many or most cases the depths whence specimens 

 caught in the net were obtained. But there can be no doubt that 

 many forms inhabit very nearly the greatest depths that have been 

 reached by the dredge, Gunther, in his "Introduction to the 

 Study o Fishes," enumerates upwards of fifty forms which are 

 supposed to have been obtained from depths exceeding 1,000 

 fathoms; twenty-six from depths exceeding 2,000 fathoms; and 

 nine from depths of 2,500 fathoms or over. Additional forms have 

 since been obtained in the dredgings of the "Talisman" and "Al- 

 batross." Bathyophis ferox and Halosaurus rostratus are reported 

 to have been dredged by the "Challenger" in water of 2,750 

 fathoms (5,019 metres), and Gonostoma microdon at an extreme 

 limit of 2,900 fathoms. Considerable doubt, however, attaches to 

 the last, since the fish is abundant in water of only moderate depth, 

 and may have been taken down in the descent of the dredge, or 

 captured only in its ascent. A similar doubt attaches to many of 

 the other forms with a reputed very broad bathymetrical range, as 

 it is hardly to be supposed that animals, organised specially to meet 

 the conditions (pressure, &c.) of life in the oceanic abyss, should 

 at the same time be so constituted as to endure with impunity the 

 very different conditions governing life near the surface. The 

 "Talisman" obtained Alepocephalus rostratus at depths stated to 

 range between 868 and 3,650 metres, Scopelus Maderensis between 

 1,090 and 3,655 metres, and Macrurus affinis between 590 and 2,220 

 metres ; similarl}', it is claimed that the ' ' Albatross " obtained 

 Cyclothone (Gonostoma) lusca and Scopelus Mulleri in depths vary- 

 ing from 560 to 5,394 metres (2,949 fathoms latitude 37 12' 

 north; longitude 69 39' west), or over a vertical extent of 16,000 

 feet. Mr. Tarlton H. Bean justly considers the deep catch as doubt- 

 ful. Less doubt attaches to the position of Aleposomus (?) Copei 

 and Mancalias uranoscopus, both of which were obtained in the 

 5,394 metre haul. 111 The deepest recorded find of the "Talis- 

 man " was in 4,255 metres (Bythites crassus)." 8 



