390 



NATURE 



[January 19, 191 i 



distribution of living organisms, and the deposits along the 

 bottom of the sea. 



It has long been a puzzle to find that at great depths 

 in the sea there are stones which are not covered by 

 deposits, though they must undoubtedly have lain at the 

 bottom for a long period of time. On the slopes of the 

 coast banks south-west of Ireland, we shot our trawl in 

 about 1000 fathoms (1797 metres), and found, inXcr alia, 

 numbers of stones. 



Sir John Murray has given them to Dr. Peach for 

 examination. As mentioned in Sir John Murray's lecture 

 to the Royal Geographical Society in Edinburgh on 

 November 11, 1910, Dr. Peach "reports that fully 20 per 

 cent, are glaciated fragments. They consist of granite, 

 gneiss, shales, sandstones, chalks, limestones, and flints, 

 and some of these contain fossil remains. The condition 

 of these fragments shows that in many instances they 

 projected above the surface of the deposit in which they 

 were embedded. Dr. Peach has no doubt that these stones 

 were carried by ice during the later phases of the Glacial 

 period to the position in which they were found. They 

 almost all belong to the series of sedimentary, metamor- 

 phosed, and erupted rocks now found in situ in this 

 country and in Ireland. But the interesting question is, 

 Why have these fragments not been completely covered 

 up by the shells which are continually falling from the 

 surface? Telegraph engineers give reasons for believing 

 that in some localities and depths the rate of accumula- 

 tion is at least i inch in ten years ; at this rate all rock 

 fragments deposited during the Glacial period should have 

 been buried in the ooze far beyond the reach of the trawl. 

 Most probably the tidal currents, which our observations 

 showed to exist in deep water, extend right down to the 

 bottom and remove the small Globigerina shells from any 

 ridges. Still, there may be other explanations of the 

 facts " (Scottish Geographical Magazine, December, 1910). 



Phytoplankton. 



The phytoplankton of the Atlantic Ocean, in so far as 

 it can be collected with tow-nets, we know from Hensen's 

 expedition in 1889, the results of which, by the way, have 

 not yet been fully treated ; further, from the extensive re- 

 searches of Cleve. We have also received a valuable con- 

 tribution from G. Murray and Whitting ; the Valdivia 

 expedition, carried out by the greater part of its investi- 

 gations in the Antarctic and Indian Oceans, the researches 

 in the Atlantic being comparatively few. Our knowledge 

 regarding the distribution of species in the Atlantic is, 

 notwithstanding, still very incomplete. 



The samples taken by tow-nets in the open sea could 

 not, any of them, compare irr quantity with what can be 

 obtained in the coastal waters in the Norwegian Sea. The 

 only exceptions are the series taken to the west of Ireland 

 and in the Bay of Biscay during April (stations 2, 3, 4, 7, 

 9, 10), where we met with large quantities of diatoms, 

 even down to depths of more than 100 metres. 



The oceanic samples are, however, very rich in species, 

 there being, as a rule, at least fifty species in every single 

 sample from the upper layers down to a depth of 100 

 metres. Many of the species are so sparsely represented 

 that it has only been possible to find a few individuals, 

 but the majority of them have, in spite of their scanty 

 numbers, a wide distribution throughout the warm seas, 

 and they have also been found in the Indian Ocean 

 (Valdivia) and the Pacific (Kofoid). A few of them have 

 not yet been described, though most of them are known 

 from previous investigations. It will be a difficult matter 

 to characterise the groups of species according to their 

 geographical distribution within the area investigated; it 

 can perhaps be done when our material has been fully 

 treated, but certainly not as yet. All we can do at present 

 is to distinguish the subtropical species from those which 

 belong to temperate waters, and the oceanic species from 

 the ones which have their centre of distribution along the 

 coasts. 



[The lecturer mentioned some instances of the occurrence 

 of interesting forms belonging to the most important 

 plankton-algae, and then described more particularly the 

 most important botanical discovery of the expedition, that 

 by centrifuging the sea-water large numbers of very small 

 algae, mostly Coccolithophorid.ne, were found. These go 



NO. 2 151, VOL. 85] 



through the meshes of the tow-nets, and have therefore nr.i 

 been considered by previous expeditions which only 1 

 tow-nets, notwithstanding that Sir John Murray, dii; 

 the Challenger expedition, had directed attention to their 

 importance.] 



'lo sum up, the chief results are as follows: — 



{i) The quantity of plankton in the open Atlanti 

 far less abundant than what is found in coastal seas. 

 , (2) At most of the stations where investigations took 

 place, the maximum of plant-substance was found at about 

 50 metres' depth ; it was, as a rule, scanty in the 

 immediate neighbourhood of the surface, but appeared to 

 be almost as abundant at 10 metres as at 50 metres. 

 There was thus about the same quantity of plants all the 

 way down from 10 metres to 50 metres. 



At 75 metres the quantity was, as a rule, not more 

 than half what we met with at 50 metres, and at 100 

 metres there was only about a tenth part. 



This was the case with oceanic water. Where there 

 was an admixture of coastal water, and an evident dis»- 

 tinction between the surface layer at depth, the surface 

 layer was comparatively richer in plants, and all the 

 limits had an upward tendency. 



(3) The different species are distributed, each in its own 

 characteristic fashion, in regard to depth. The PeriiT 

 keep comparatively near the surface, the diatoms jir 

 the deepest layers, while the Coccolithophoridae affeci .... 

 intermediate position. 



{4) The number of living plant cells in the open Atlantir 

 throughout the most densely populated water-!.; 

 (10-50 metres) varies, as a rule, between 3000 and 1. 

 cells per litre sea water. Of these, about half are Cot co 

 lithophoridse, the rest being Peridinea cells with a few 

 naked flagellates and a sprinkling of diatoms. 



The Larger Organisms. 

 Deep-sea Fishes and Crustaceans. 



Since the Challenger expedition laid the first foundatloi 

 pf our knowledge regarding the animal world of the •' 

 sea, many succeeding expeditions have bountifully a 

 to our store. .As an instance, I may mention thai 

 now know one thousand different species of deep-sea fi- 

 and that the German Valdivia expedition alone discovci^' 

 no fewer than sixty-three new species. 



Regarding these many species, however, only very littl 

 is known. In the case of quite a number of them we ar 

 acquainted merely with one, or at most a few specimens 

 while we are in almost complete ignorance as to the! 

 biologv, their propagation, development history, growth 

 and outward conditions of life. 



The view which generally prevails in literature nowaj 

 days is that tlie sea contains a motley abundance of fern ' 

 either along its bottom or floating within its w:r 

 subject to a uniformity of outward conditions of exis: 

 — that is to sav, passing their lives in absolute darkn 

 and in a medium with constant temperatures and < 

 physical surroundings. 



To biologists, this view concerning the animal lit 

 the deep sea has presented many difficulties. How > 

 Ithat in a constant medium of the kind conceived theii 

 exist side hy side so many distinct forms? -And hovl 

 again, can animals with large -eyes manage to live al- 

 side blind forms? Why are some species furnished 

 numerous highly developed light-organs, while in the <... 

 of others these are entirely wanting? .And_ how, tO(j 

 comes it that within the same groups of animals, na' 

 often in closely affinitive species, the colours vary 

 remarkablv, although the outer medium is the same? 



These questions have become all the more pressing no : 

 that biological ocean research has discovered instanr<j 

 where in the same area of the sea there occur m-'- 

 different animal forms, each possessed of its own pecul 

 ties in mode of life, habitat, and other respects, so ;_ 

 each species has its own characteristic area of distrib] 

 tion, even though it may occasionally be found togethi 

 with its neighbours in the same catch. Our study of 

 spawning-grounds of the cod family (Gadidae) in 

 North Sea and Norwegian Sea has shown us, for inst. 

 that each of seventeen species has its particular spaw 

 area, each species during the spawning period seekin;; 

 distinct characteristic depths, temperatures, and salin. 



