April 22, 1880] 



NATURE 



59i 



DEEP-SEA DREDGING AND LIFE IN THE 

 DEEP SEA ' 



III. 



HOW is it that the general absence of ancient forms from 

 the deep sea is to be accounted for? It is hardly 

 probable that the struggle for existence in the great depths 

 is very severe. The fact that so helpless an animal as a 

 Pycnogonid can grow to a length of two feet points to the 

 existence of easy conditions of life. Even if the struggle 

 in the deep sea were as great as in shallow water we 

 might have expected that it would extinguish these 

 different forms from those which it exterminated near the 

 shores. It seems on the whole probable that the deep 

 sea may have been entirely devoid of life during the 

 earlier geological epochs. The modifications existing in 

 deep-sea animals as adaptations to their special modes of 

 life are not much more important than those exhibited by 

 animals inhabiting caves of comparative recent origin, 

 such as Proteus or those living in the deep waters of the 

 larije lakes of Europe, which are also of no great antiquity, 

 such as the air-breathing water-snails, which, from the 

 necessities of deep-water life, have adapted their lungs to 

 aquatic respiration. A long time has not therefore been 

 required for these modifications to take place. 



It has been, I believe, commonly assumed that the 

 water of the ocean was originally fresh, or nearly so, and 

 that it became gradually Salter as the rivers brought into 

 it salts as part of the products of denudation. But surely 

 the primitive sea must have been highly charged with 

 saline matters of all kinds. 



When the earth was still intensely heated, the whole of 

 the water now on its surface must have been present as 

 gas in its atmosphere, at first no doubt dissociated, but 

 afterwards as aqueous vapour. Since if the sea-bottom 

 and continents were smoothed down to a uniform level, 

 the sea would still suffice to cover the entire earth to a 

 depth of over 1,000 fathoms, aqueous vapour equal to a 

 layer of water of that thickness must have existed in the 

 atmosphere and have produced a pressure of more than 

 a ton on the square inch at the earth's surface. To 

 this pressure must have been added that produced by all 

 the other vapours with which the primitive atmosphere 

 must have been filled. As the earth cooled the water 

 condensed on the coolest spots from time to time, boiled, 

 and rose as vapour again. Mr. Mallet 2 conjectures that 

 the first water formed on the earth's surface may have 

 been even as hot as molten cast-iron. At last permanent 

 seas were established. The waters of these heated to an 

 intensely high temperature under great pressure must have 

 dissolved salts in abundance from the freshly consoli- 

 dated earth's crust, and being constantly in a state of 

 ebullition as the pressure diminished at the surface with 

 the growth of the seas, or the temperature of the earth's 

 surface varied in different places, must have taken up 

 vast quantities of rock-matter in suspension and become 

 thickly charged with volcanic mud. Intensely hot rain 

 must have fallen on the land and have washed down 

 more salts and mud into the sea. The whole ocean must 

 have consisted of a vast mass of seething mud. 



It must have required a protracted period for the ocean 

 to become clear, and for its deposit, which was perhaps 

 somewhat like the present deep-sea red mud, to settle, 

 and possibly the deeper water long remained uninhabit- 

 able, being overcharged with various gases and salts and 

 suspended mud. In connection with the question of the 

 probable development of the earliest forms of life in 

 heated water holding abundant salts and gases in solution, 

 it is of importance to note that various alga: at present 



1 Friday Evening Lecture delivered at ihe Royal Institution on March 5. 

 by H. N. Moseley, F.R.S., Assistant Registrar of the University of London. 

 Continued from p. 572. 



= R. Mallet "tin the Pi. Lai!.- Temperature of the Primordi 

 ." Quart. ?.■■. 0, p. 115. 



thrive in very hot mineral springs in various parts of the 

 world. 1 



To this original deposit of mud on the deep ocean floor 

 the deposits which have since been formed possibly bear 

 but a slight proportion in thickness, for it must not be 

 forgotten that all the Globigerina mud and other organic 

 deposits now in course of formation on the sea bed are 

 ultimately derived from the land. The Globigerinas 

 merely distribute the lime washed down by the rivers 

 more evenly over the ocean floor, by concentrating it in 

 the substance of their shells. The organic muds are in 

 their origin products of denudation, and if the whole land 

 now above the sea were washed into the ocean and evenly 

 distributed a deposit of only about 500 feet in thickness 

 would result. 



Ft :. iS. — UmbcUuU GntntandU*. 



I shall, in conclusion, speak of some of the physiologi- 

 cal conditions of life in the deep sea. Deep-sea animals, 

 as a rule, have either no eyes at all or have very large 

 eyes. As an example may be cited the crustacean, 

 Astaats zalencus, most closely allied to the common cray- 

 fish which Prof. Huxley has lately made illustrious. It 

 is from 450 fathoms. It has no eyes at all, but one of 

 its nippers is extraordinarily long and delicate, and pos- 

 sibly the animal uses it to feel its way with, as a blind 

 man uses his stick. There are also abundant hairs on 

 the animal's surface, which are probably organs of touch. 



Many deep-sea Crustacea, however, and fish have very 

 large eves indeed, evidently for the purpose of making. 

 1 See "Nctes by a Naturalist," rp :- 6 . 



