8i6 



NATURE 



[August 26, 1920 



known factors may enter into every problem. The 

 samples required may be at the other end of a rope 

 or a wire eight to ten miles long, and the oceano- 

 grapher may have to grope for them literally in the 

 dark and under other difticult conditions which make 

 it uncertain whether his samples when obtained are 

 adequate and representative, and whether they have 

 undergone any change since leaving their natural en- 

 vironment. It is not surprising, then, that in the 

 progress of knowledge mistakes have been made and 

 corrected, and that views have been held on what 

 seemed gpod scientific grounds which later on were 

 proved to be erroneous. For example, Edward 

 Forbes, in his division of life in the sea. into zones, 

 on what then seemed to be sufficiently good observa- 

 tions in the ^gean, but which we now know to be 

 exceptional, placed the limit of life at 300 fathoms, 

 while Wyville Thomson and his fellow-workers on the 

 Porcupine and the Challenger showed that there is no 

 azoic zone even in the great abysses. 



Or, again, take the celebrated myth of Bathybius. 

 In the sixties of last century samples of Atlantic 

 mud, taken when surveying the bottom for the first 

 telegraph cables and preserved in alcohol, were found 

 when examined by Huxley, Haeckel, and others to 

 contain what seemed to be an exceedingly primitive 

 protoplasmic organism, which was supposed on good 

 evidence to be extended widely over the floor of the 

 ocean. The discovery of this Bathybius was said 

 to solve the problem of how the deep-sea animals 

 were nourished in the absence 01 seaweeds. Here 

 was a widespread protoplasmic meadow upon which 

 other organisms could graze. Belief in Bathybius 

 seemed to be confirmed and established by Wyville 

 Thomson's results in the Porcupine Expedition of 

 1869, but was exploded by the naturalists on the 

 Challenger some five years later. Buchanan in his 

 recently published "Accounts Rendered " tells us how 

 he and his colleague Murray were keenly on the look- 

 out for hours at a time on all possible occasions for 

 ■traces of this organism, and how they finally proved, 

 in the spring of 1875 on the voyage between Hong- 

 Kong and Yokohama, that the all-pervading substance 

 like coagulated mucus was an amorphous precipitate 

 of sulphate of lime thrown down from the sea-water 

 in the mud on the addition of a certain proportion 

 of alcohol. He wrote to this effect from Japan to 

 Prof. Crum Brown, and it is in evidence that after 

 receiving this letter Crum Brown interested his friends 

 ,in Edinburgh by showing them how to make Bathy- 

 bius in the chemical laboratory. Huxley at the 

 Sheffield meeting of the British Association in 1879 

 handsomely admitted that he had been mistaken, and 

 it is said that he characterised Bathybius as " not 

 having fulfilled the promise of its youth." Will any 

 of our present oceanographic beliefs share the fate of 

 Bathybius in the future? Some may, but even if they 

 do they may well have been useful steps in the pro- 

 gress of science. Although, like Bathybius, they may 

 not have fulfilled the promise of their youth, yet we 

 may add they will not have lived in the minds of 

 man in vain. 



Many of the phenomena we encounter in oceano- 

 graphic investigations are so complex, are or may be 

 affected by so many diverse factors, that it is difficult, 

 if indeed possible, to be sure that we are unravelling 

 them aright and see the real causes of what we 

 observe. 



Some few things we know approximately, nothing 

 completely. We know that the greatest depths of the 

 ocean, about six miles, are a little greater than the 

 highest mountains on land, and Sir John Murrav has 

 calculated that if all the land were washed down into 

 the sea the whole globe would be covered by an ocean 

 NO. 2652, VOL. 105] 



averaging about two miies in depth.* We know the 

 distribution of temperatures and salinities over a great 

 part of the surface and a good deal of the bottom of 

 the oceans, and some of the more important oceanic 

 currents have been charted and their periodic varia- 

 tions, such as those of the Gulf Stream, are being 

 studied. We know a good deal about the organisms 

 floating or swimming in the surface waters (the epi- 

 plankton), and also those brought up by our dredges 

 and trawls from the bottom in many parts of the 

 world, although every expedition still makes large 

 additions to knowledge. The region that is least 

 known to us, both in its physical conditions and in 

 its inhabitants, is the vast zone of intermediate waters 

 lying between the upper few hundred fathoms and 

 the bottom. That is th6 region that Alexander 

 Agassiz, from his observations with closing tow-nets 

 on the Blake Expedition, supposed to be destitute of 

 life, or at least, as modified by his later observations 

 on the Albatross, to be relatively destitute compared 

 with the surface and the bottom, in opposition to the 

 contention of Murray and other oceanographers that 

 an abundant meso-plankton was present, and that 

 certain groups of animals, such as the Challengerida 

 and some kinds of Medusae, were characteristic of 

 these deeper zones. I believe that, as sometimes 

 happens in scientific controversies, both sides were 

 right up to a point, and both could support their views 

 upon observations from particular regions of the ocean 

 in certain circumstances. 



But much stijl remains unknown or only imper- 

 fectly known even in matters that have long been 

 •studied and where practical applications of great value 

 are obtained — such as the investigation and prediction 

 of tidal phenomena. We are now told that theories 

 require reinvestigation, and that published tables are 

 not sufficiently accurate. To take another practical 

 application of oceanographic work, the ultimate causes 

 of variations in the abundance, in the sizes, in the 

 movements, and in the qualities of the fishes of our 

 coastal industries are still to seek, and, notwithstand- 

 ing- volumes of investigation and a still greater volume 

 of discussion, no man who knows anything of the 

 matter is satisfied with our present knowledge of even 

 the best-known and economically most important of 

 our fishes such as the herring, the cod, the plaice, 

 and the salmon. 



Take the case of our common fresh-water eel as an 

 example of how little we know and at the same time 

 of how much has been discovered. All the eels of 

 our streams and lakes of North-West Europe live and 

 feed and grow under our eyes without reproducing 

 their kind; no spawning eel has ever been seen. 

 After living for years in immaturity, at last near the 

 end of their lives the large male and female yellow- 

 eels undergo a change in appearance and in nature. 

 They acquire a silvery colour and their eyes enlarge, 

 and in this bridal attire they commence the long 

 journey which ends in maturity, reproduction, and 

 death. From all the fresh waters they migrate in the 

 autumn to the coast, from the inshore seas to the 

 open ocean and still westward and south to the mid- 

 Atlantic, and we know not how much further, for 

 the exact locality and manner of spawning have still 

 to be discovered. The youngest known stages of the 

 Leptocephalus, the larval stage of eels, have been 

 found by the Dane, Dr. Johannes Schmidt, to the 

 west of the Azores, where the water is more than 

 2000 fathoms in depth. These were about one-third 

 of an inch in length, and were probably not long 

 hatched. I cannot now refer to all the able inves- 



* It was DO'ssibly in such a former wrrM-wide ocean of ionised water that, 

 according to the recent speculations of A. H. Church (" Thalassiophyta," 

 igiq), the first living oreanisms were evolved, to become later the floating 

 unicelhilar plants of the primitive plankton. 



