592 



NATURE 



{April 22, 1880 



use of some small quantity of light which must exist in 

 all depths. In the absence of sunlight the only other 

 source of light must be the phosphorescence of certain 

 of the deep-sea animals themselves. Dr. Carpenter, Sir 

 Wyville Thomson, and Mr. Gwyn Jeffreys came to this 

 conclusion after some of their early deep-sea dredgings. 

 There can be little doubt of its correctness. 



Here (Fig. 16) is a deep-sea Alcyonarian, UmbeHula 



17.— Ptttith 



, Wyville Thomson. 



Creenlandica, so named because it was first obtained off 

 Greenland, being, like the deep-sea fish I exhibited, an 

 example of a deep-sea form extending into shallow water 

 in high latitudes. Umbellula consists of a bunch of polyps 

 supported on the end of a long flexible stem, which is 

 cut off short in the figure. This specimen was from 2,175 

 fathoms between Madeira and the Spanish coast. When 

 it came to the surface it emitted a most brilliant phos- 



phorescent light, as did also many allied forms dredged in 

 deep water. No doubt these animals, like their congeners 

 in shallow water, emit light in the deep sea ; and the deep- 

 sea animals with eyes probably congregate round them or 

 grope their way in the gloom from one bunch to another 

 as they lie scattered over the bottom, just as we half-feel, 

 half-see our way from lamp-post to lamp-post at night in a 

 London fog. Some lose their way, as we do sometimes, 

 and get into shallow water, and a good 

 many deep-sea animals have been from 

 time to time picked up near the shores 

 at Madeira and elsewhere, and have 

 found their way into museums as great 

 rarities. 



No doubt the sense of touch is the one 

 mainly relied on by most deep-sea 

 animals. Very many are provided with 

 special organs of touch, such as long 

 hairs, or in the case of fish enormously 

 long fin-rays. Unfortunately we did not 

 examine the organs of hearing of any of 

 the deep-sea animals which we dredged. 

 Nearly all were far too precious to be 

 dissected. Possibly some of the animals 

 have the sense of hearing highly de- 

 veloped. 



There is plenty of oxygen for respira- 

 tion in the deep sea. Mr. Buchanan 

 found that water from even 4,475 fathoms 

 contained 4'o6 cubic centimetres of oxy- 

 gen to the litre, nearly as much as at 

 the surface, where, however, the amount 

 varies greatly, rising to as much as 7 

 cubic centimetres per litre. The smallest 

 amount observed was '6 of a cubic centi- 

 metre per litre in a depth of 2,875 

 fathoms. Even this amount would pro- 

 bably support life, for Humboldt and 

 Provencal showed that tench could still 

 breathe, though with difficulty, in water 

 containing only one-third of that quantity 

 of oxygen. 



Life must be very monotonous in the 

 deep sea. There must be an entire ab- 

 sence of seasons, no day and night, no 

 change of temperature. Possibly there 

 is at some places a periodical variation 

 in the supply of food falling from above, 

 which may give rise to a little annual 

 excitement amongst the inhabitants. 



There being no plants in the deep sea 

 except parasites, the ultimate sources of 

 food must be derived entirely from above, 

 from the falling to the bottom of dead 

 surface animals and plants, and of the 

 debris washed from the shores. Sea- 

 water acts as a most efficient preserva- 

 tive of animal tissues, and possibly at no 

 very great depths and at the deep-sea 

 bottom Bacteria may be entirely absent, 

 so that decomposition in the form in 

 which we are commonly acquainted with 

 it does not there take place at all. 



From experiments which I made on 



the rate of sinking of a dead Salpa I 



found that it would reach the bottom at 



2,000 fathoms in four days, in which time it would even 



at the surface be hardly decomposed at all. It would thus 



afford good food to the bottom animals. 



A large quantity of shore debris and vegetable matter 

 carried down by rivers reaches the deep-sea bed. We 

 found leaves, branches, and fruits in deep water, and one 

 of the latter had its interior still fresh, and was full of 

 animals feeding upon it. Mr. Agassiz found in depths of 



