HABITS OF MARINE ANIMALS 155 



plankton must be added the myriads of floating eggs 

 and helpless larvae of marine fishes. 



Transitory plankton, as will be seen later, materially 

 adds to the food supply in the sea, and, further, the 

 fact of its drifting about has an important bearing on 

 the distribution of various forms of marine life. As 

 the seeds of plants and trees on the land are carried 

 hither and thither by the wind, so similarly the larvae of 

 marine animals are carried through the ocean by tides 

 and currents. In this manner marine life is main- 

 tained in more or less the same proportions all over the 

 world, whatever may be the agencies working for its 

 destruction. 



As the pastures of the land die down in winter, and 

 life lies dormant, so in the sea plankton dies down ; 

 but the sea is never altogether sterile, for copepods are 

 always present, as well as many other varieties of small 

 crustaceans. 



With the advent of spring, the sea is flooded with the 

 eggs of spring-spawning fish, such as the plaice, the 

 haddock and the cod, and these very soon hatch into 

 the various larval forms. Simultaneously the minutest 

 forms of plankton life (protozoa and diatoms) increase 

 in the miraculous manner described ; while the larvae 

 of the barnacles, sea-squirts, crabs and copepods appear 

 in their myriads. In June, July and August the sea 

 is full of the eggs and larvae of summer-spawning fishes, 

 such as the ling, the mackerel, the turbot, and the sole. 

 The diatoms have now eased off and though the crab 



