THE ORIGIN OF THE OLDEST FOSSILS, ETC. 277 



abundance that there were some in every bucketful of water which 

 we dipped up, nor is this abundance of life restricted to tropical 

 waters, for Haeckel tells us that he met with such enormous masses 

 of Lwiacina to the north west of Scotland, that each bucket of 

 water contained thousands. 



The tendency to gather in crowds is not restricted to the 

 smaller 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, and we are told of one school which 

 was a windrow of fish half a mile wide and at least twenty miles 

 long. But while pigeons are plant eaters, the mackerel are rapa- 

 cious hunters, pursuing and devouring the herrings as well as other 

 animals. 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 

 herring are also carnivorous, each one consuming myriads of 

 copepods every day. 



In spite of this destruction and the ravages of armies of medusae 

 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 power of comprehen- 

 sion. 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 discolour the water for miles. We know, too, that 

 they are not restricted to the surface, and that the banks of cope- 

 pods are sometimes more than a mile thick. When we reflect that 

 thousands would find ample room and food in a pint of water, one 

 can form some faint conception of their universal abundance. 



The organisms which are visible 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 blue-fish, are never satis- 

 fied with slaughter, but kill for mere sport. 



Insatiable rapacity must end in extermination unless there is 

 some unfailing supply, and as we find no visible supply in the 

 water of the ocean we must seek it with a microscope, which shows 

 us a wonderful fauna made up of innumerable larvae and embryos 



