1054 EEPORT OF COMMISSIONER OF FISH AND FISHERIES. [10] 



when young, but later grows into large, rounded, sulphur-yellow masses, 

 often a foot in diameter. In deep water other species occur. Rarely, 

 we dredge up, on the outer grounds, fragments of wood, but these are 

 generally perforated by tbe borings of bivalves {nsuaUj Xylophaga dor- 

 salis) and other creatures, and are evidently thus soon destroyed. Very 

 rarely do we meet with the bones of vertebrates at a distance from the 

 coast. Although these waters swarm with vast schools of fishes, while 

 sharks and a large sea-porpoise or (>olphin {Dclphinus cJelplds) occur in 

 large numbers, we have, very rarely indeed, dredged up any of their 

 bones, or, in fact, remains of any other vertebrate animals. In a few in- 

 stances we have dredged a single example of a shark's tooth, and oc- 

 casionally the hard otoliths of fishes. It is certain that not merely the 

 flesh, but most of the bones, also, of all vertebrates that die in this 

 region are very speedily devoured by the various animals that inhabit 

 the bottom. Echini are very fond of fish-bones, which they rapidly con- 

 sume. 



Relics of man and his works are of extremely rare occurrence, at a 

 distance from the coast, or outside of harbors, with the exception of the 

 clinkers and fragments of coal thrown overboard with the ashes from 

 steamers. As our dredgings are in the track of European steamers, 

 such materials are not rare. A few years ago even these would not 

 have occurred. A rock forming on this sea-bottom would, therefore, 

 contain little evidence of the existence of man, or even of the existence 

 of the commonest fishes and cetaceans inhabiting the same waters. 



EVIDENCES OF THE EXISTENCE OF LIGHT AT GREAT DEPTHS. 



The evidences of the presence of light at great depths and its quality 

 and source are of much interest. At present very little experimental 

 knowledge in regard to these questions is available. That light of some 

 kind and in considerable amount actually exists at dejiths below 2,000 

 fathoms may be regarded as certain. This is shown by the presence of 

 well-developed eyes in most of the fishes, all of the Cephalopods, most 

 of the decapod Crustacea, and in some species of other groups. In 

 many of these animals living in 2,000 to 3,000 fathoms, and even deeper 

 than that, the eyes are relatively larger than in the allied shallow- water 

 species; in others the eyes differ little, if any, in size and appearance 

 from the eyes of corresponding shallow- water forms; in certain other 

 cases, especially among the lower groui)S, the eyes are either rudimen- 

 tary or wanting in species of which the shallow-water representatives 

 have eyes of some sort. This last condition is notable among the deep- 

 water Gastropods, which are mostly blind, but many of these are prob- 

 ably burrowing species, and it may be that the prevalent extreme soft- 

 ness of the ooze of the bottom and the general burrowing habits are 

 connected directly with the absence or rudimentary condition of the 

 eyes in many species belonging to different classes, including Crustacea 

 and fishes. Such blind species usually have highly-developed tactile 

 organs, to compensate for lack of vision. 



