146 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



about two miles, a multitude of pelagic animals which would be incred- 

 ible to those who have not witnessed it. 



The naturalists of the Challenger found the waters of the equatorial 

 Pacific swarming with life, not at the surface alone, but in its deeper 

 layers, and the ship often sailed through great banks of pelagic animals. 



The equatorial Atlantic is like the Pacific, and Chiercha says that its 

 zone of equatorial calms is rich beyond all measure in animal life, and 

 that the water often looks and feels like coagulated jelly. 



Of the Indian Ocean, Haeckel says that in his voyage to and from 

 Ceylon he was wonderstruck with the wealth of pelagic life day after 

 day on the mirror-like surface. At night it was an unbroken sheet of 

 sparkling light as far as the eye could reach, and the water which was 

 dipped up at random held such a thick swarm of densely crowded 

 luminous animals (Ostracods, Salpa, Pyrosomas, and Medusae) that a 

 printed book could be read distinctly in a dark night by this pelagic light. 



In temperate and arctic waters there is less diversity, but, as Haeckel 

 shows, there is no evidence of any decrease in individuals, and banks of 

 pteropods (Clio and Limacina), so dense that they seem almost solid, are 

 met even beyond the arctic circle. 



Haeckel says that in a cruise to the northwest of Scotland he met 

 with such enormous masses of Limacina that each bucket of water which 

 was dipped up contained thousands. 



The tendency to gather in crowds is not restricted to the smaller 

 pelagic animals, and many species of raptorial fishes are found in 

 densely packed banks. 



The fishes in a school of mackerel are as numerous as the birds in a 

 flight of wild pigeons. Goode, in his History of Aquatic Animals, tells of 

 one school of mackerel which was estimated to contain a million barrels, 

 and of another which was a windrow of fish half a mile wide and at least 

 twenty miles long ; but while the pigeons are plant-eaters, the mackerel 

 are rapacious hunters, pursuing and devouring the herrings, as well as 

 the pteropods and pelagic Crustacea. 



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

 In 1879 three hundred thousand river herring were landed in a single 

 haul of the seine in Albemarle Sound ; but the herrings are also carniv- 

 orous, each one consuming myriads of copepods every day. In spite of 

 this destruction and the ravages of armies of medusas 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. 



