96 SEA FISHERIES 



understand why Calvados Bay is richer in plankton than 

 Granville Bay. It is true that the alluvia of the Seine 

 contribute a certain amount of material to the former 

 bay ; but they are infinitely less than those of the great 

 German rivers, which throw their deposits as far as the 

 Dogger, or than those of Cabot's current. 



To sum up, plankton and current are synonymous. 

 This formula has the advantage of connecting the 

 oceanographical study of plankton, which terminates 

 here, with the chemical study of it, the principal elements 

 of which I am about to enounce. 



VIII 



Vegetable plankton is the prime cause of chemical 

 action in the ocean. This it is, as we know, that trans- 

 forms into living material the inorganic substances 

 dissolved in the water. The animal plankton lives at the 

 expense of the vegetable plankton, which it absorbs. 

 The larger marine animals consume either vegetable or 

 animal plankton, or animals smaller than themselves 

 which are nourished on plankton. Such is the general 

 scheme of oceanic life. The quantity of vegetable 

 plankton is in direct proportion to the mass of soluble 

 nutritive substances. The marine plants would nourish 

 themselves upon these soluble substances until the latter 

 were exhausted, were it not that they are constantly 

 renewed by the perpetual action of the currents. 

 It is to this perpetual movement of the waters that the 

 development of vegetable plankton is due. Naturally 

 an equilibrium is produced between vegetable and 

 animal plankton (as M. Gruvel has proved in his 

 experiments off the coast of West Africa), so that the 

 regions richest in vegetable plankton are often the 

 poorest in animal plankton. In other words, the 



