ORIGIN OF THE FOOD OF MARINE ANIMALS. 91 



plant-eaters, the mackerel are rapacious hunters, pursuing and devouring the her- 

 rings, as well as the pteropods and pelagic Crustacea. 



Herring swarm like locusts, and a herring bank is almost a solid wall. In 1879 

 300,000 river herring were landed by a single haul of the seine in Albemarle 

 Sound ; but the herrings are also carnivorous, each one consuming myriads of copepods 

 every day. In spite of this destruction and the ravages of armies of medusa; and 

 siphonophores and pteropods, the fertility of the copepods is so great that they are 

 abundant in all parts of the ocean, and they are met with in numbers which exceed 

 our powers of comprehension. 



On one occasion the Challenger steamed for two days through a dense cloud formed 

 of a single species, and they are found in all latitudes from the Arctic regions to 

 the equator, in masses which discolor the water for miles. We kuow, too, that they 

 are not restricted to the surface, and that the banks of copepods are sometimes a mile 

 thick. When we reflect that thousands would find ample room and food in a pint of 

 water, we can form some faint conception of their universal abundance. 



As the result of our view, we find that the organisms which are visible without 

 a microscope in the water of the ocean and on the sea bottom are almost universally 

 engaged in devouring each other, and many of them, like the bluefish and the alba- 

 core, are never satisfied with slaughter, but kill for mere sport. 



Insatiable rapacity must end in extermination unless there is some unfailing sup- 

 ply, and as we find no visible supply in the water of the ocean we must seek it with 

 a microscope. By its aid we find a wonderfully rich and diversified fauna made up of 

 innumerable larvre of all sorts of marine animals, together with a few minute and 

 simple metazoa, but these things can not form the food supply of the ocean. It is 

 clear that a single carnivorous animal could not exist very long by devouring its own 

 children, and the result must be the same, however great the number of individuals 

 or species. 



The total amount of these organisms is inconsiderable, however, when compared 

 with the abundance of a few forms of j)rotozoa and protophytes, and both observa- 

 tion and deduction force us to recognize that the most important element in the total 

 amount of marine life consists of some half a dozen types of protozoa and unicellular 

 plants, of globigerime and radiolarians, and of trichodesmium, pyrocystis, protococcus, 

 and the coccospheres, rhabdospheres, and diatoms. 



Modern microscopic research has shown that these simple plants, and the globig. 

 erinse and radiolariang which feed upon them, are so abundant and prolific that they 

 meet all demands and supply the food for all the animals of the ocean. This is the 

 fundamental conception of marine biology. The basis of all the life in the modern 

 ocean is to be sought in the microorganisms of the surface. 



This is not all. The simplicity and abundance of the microscopic forms and their 

 importance in the economy of nature show that the organic world has gradually shaped 

 itself around and has been controlled by them. They are not only the fundamental 

 food supply, but the primeval supply, which has determined the whole course of the 

 evolution of marine life. 



The pelagic plant-life of the ocean has retained its primitive simplicity on account 

 of the very favorable character of its environment, and the higher rank of the littoral 

 vegetation and that of the land is the result of hardship. 



