242 FOUNDERS OF OCEANOGRAPHY 



depths with certain biological conditions is determined, is 

 in any case of much more value for many questions than 

 vertical hauls or investigation of water-samples, which are 

 taken to be representative of a whole column of water from 

 the surface to a definite depth. The result of these latter 

 methods, which have been used especially by the Kiel 

 naturalists, is, that the interesting details found on com- 

 paring the plankton flora at different depths disappear in 

 an average, which often has a very doubtful value. In 

 any case, it is better, as Lohmann has done, to calculate 

 the average for the plankton of the whole column of water, 

 after reliable and exact observations have been made at 

 definite depths." So far Gran, who may be regarded as 

 a very reHable authority. 



Now these are cases of catches taken in shallow water 

 or in coastal areas, and it may be said — it has been said — 

 that results may be very different out on the high seas far 

 from land where the conditions are more constant and the 

 plankton ought to be more regularly distributed ; but when 

 we look at the evidence that is available we find that there 

 is much that tells the other way. Many naturahsts on 

 long voyages have told of the swarms of some planktonic 

 organism met with in quite limited areas — organisms such 

 as Trichodesmium, Medusce, Salpa, Physalia and Clione. 

 Most of these are members of the macro -plankton, it is true, 

 but macro-plankton is of the greatest importance as the 

 food of fishes and whales. Then, to record 'a personal 

 experience, I have examined the plankton daily on twelve 

 ocean traverses, through the North and South Atlantic, 

 the Indian Ocean, and the great expanse of the Southern 

 Ocean (going to North America, to South Africa, to Ceylon, 

 and to Austraha), caught by means of fine silk nets on taps 

 with sea-water running day and night, and the variations 

 from day to day have usually been very marked, and not 

 in the macro-plankton only, but also in the case of the 

 Diatoms and Peridinians belonging to the micro- or nanno- 



