2 MARIN?:: AND FISHERIES 



5 GEORGE v., A. 1915 



ming larvse and the metamorphosis of starfishes and sea-urchins at Heligoland 

 between 1845 and 1855. 



An enormous advance in the qualitative description of the Plankton of the 

 five oceans resulted from the collections and observations accumulated during 

 the voyage of H.M.S. Challenger (1873-1876). 



The , intensive quantitative determination of the Plankton was inaugurated 

 by Professor Hensen, who led the well-known Plankton Expedition in the 

 Atlantic Ocean in 1889. The finely illustrated reports which have been issued 

 from that time to this, sufficiently attest the value of the results obtained; but the 

 actual significance of the countings and calculations can only be appreciated fully 

 by professional statisticians. 



The principal object aimed at by the promoters of the Plankton Expe- 

 dition was a physiological one: the discovery of the factors which control 

 the metabolism of the sea, i.e., the assimilation and interchange of nutritive 

 materials under the influence of light, heat, and oxygen, on the part of pelagic 

 organisms which have no place in popular esteem, but which nevertheless are 

 the prime sustenance of all the marketable food-fishes. 



The scientific interpretation of the Plankton is thus a physiological problem 

 and its bearing upon human welfare lies in opening the way to a rational conception 

 of the fertility of the sea. The prodigality of marine life in its less conspicuous 

 aspects is a natural phenomenon which must be investigated by methods as rigorous 

 as those that are applied to the elucidation of other natural phenomena, in order 

 that progress may be reported all along the line. It is impossible to avoid the 

 problem; and the multiplication of biological stations in all the progressive coun- 

 tries of the world, proves that it is impossible to rest contented with temporary 

 achievements, however brilliant they may appear to be. 



After the quantitative method has been adequately tested, the next way of 

 dealing with the great question of the metabolism of the sea is the experimental 

 method. Perhaps unnecessary emphasis has been laid upon the distinction be- 

 tween observation and experiment, although it is by no means easy at all times 

 to draw the line of demarcation. When Pasteur in 1860 drove the last nail into 

 the coffin of the doctrine of the spontaneous generation of micro-organisms, the 

 contrast between the methods of observation and experiment was indeed brought 

 into high relief by the futile opposition of an otherwise excellent zoologist, Georges 

 Pouchet, whose name is perpetuated by its having been applied to a peculiar 

 member of the 'micro-plankton, Pouchetia. 



This is one of the Flagellata, distantly related to a very common species at 

 St. Andrew's named Peridinium divergens, shaped like a miniature chafing-dish 

 with a conical cover, which is probably responsible, at least in part, for the display 

 of phosphorescence to be witnessed there, according to the testimony of the staff 

 at the Biological Station. Of course Pouchet's opposition to Pasteur was the one 

 sad mistake of his life, but he did much good work besides. Amongst many other 

 things, he reported upon the Sardine Industry of France. On one occasion, in 

 company with a colleague, he found the stomachs of the sardines which they were 

 examining, filled with Peridinium divergens and an allied species of the same 



