12 A NATURAL HISTORY OF THE SEAS 



and having little bearing upon practical matters, far less 

 world economy. With each succeeding year, however, 

 the complex interdependence of all animate nature is being 

 more fully appreciated and it may well be that the plankton 

 taken by some scientist to-day may bear indirectly but not 

 the less forcibly upon human welfare several decades 

 hence. It is generally recognized, for example, that all 

 marine life is ultimately dependent for its being on the 

 myriad microscopic plants that throng the waves in the 

 spring and early autumn. They constitute the first link 

 in what is nowadays generally termed the " food chain." 

 As an example it may be pointed out that such plants form 

 the basis of food which nourishes the minute creatures 

 that go to feed the first stages of the herring and many 

 other food fishes. The larger herring itself eats its smaller 

 brethren, whilst sea birds, large fish, seals, whale and man 

 depend largely upon the herring for their sustenance. 

 It will be appreciated, therefore, that plankton and all 

 the factors which control its rise and fall are matters of 

 primary importance and much more than a mere academic 

 study for the laboratory worker. 



In the following pages the marine fauna of the world 

 will be dealt with in scientific order, though only those 

 creatures of more striking interest or more obvious im- 

 portance to human welfare can be touched upon in any 

 detail. 



