INTERNAL ECONOMY OF THE SEA 81 



Dr. W. J. Dakin showed that the Copepods, in 

 turn, feed largely on the drifting plant-organisms 

 of the surface waters, such as Diatoms, and on 

 Infusorian-like animals called Peridinians. But 

 the multiplication of these minute organisms de- 

 pends in the main on the amount of sunshine. So 

 that the more sunshine, the more mackerel. One 

 incarnation follows another, Copepod after Diatom, 

 Mackerel after Copepod, Man after Mackerel an 

 illustration of Liebig's luminous idea of the circula- 

 tion of matter. 



The producers of the wealth of the sea are the 

 chlorophyll-possessing organisms, most of which are 

 indubitable plants, though a few incline to the 

 animal persuasion. Of the plants there are two 

 great groups: (a) the minute Algas of the super- 

 ficial layers of the open sea (the Phyto-plankton), 

 and (6) the sea-grass, the larger seaweeds, and the 

 attendant micro-flora, abounding in the shore area 

 in the wide sense. Though many of the seaweeds 

 have also brown or red pigment, all have chloro- 

 phyll. And by virtue of this we do not know how 

 they are able to utilize the energy of the sunlight 

 to build up the simple constituents of air and sea- 

 water into complex organic products which in turn 

 form the food of animals. On this power of photo- 

 synthesis depends the whole economy of marine as 

 of terrestrial life. It is very generally believed 

 that the chief producers are the minute and simple 

 Algae of the open waters which form in certain 

 areas which Sir John Murray used to call " floating 



