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 Algz 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 
Algze of the open waters which form in certain 
areas which Sir John Murray used to call “ floating 
