THE ORIGIN OF THE OLDEST FOSSILS, ETC. 463 



its mouth and gathered a host of small fishes to snatch the 

 fragments as they drifted away with the tide. 



Many important fishes, like the cod, pasture on the bottom, 

 but their pasturage consists of molluscs and annelids and 

 Crustacea instead of plants, and the vast majority of sea fishes 

 are fierce hunters, pursuing and destroying smaller fishes, and 

 often exhibiting an insatiable love of slaughter, like our own blue 

 fish and tropical albacore and barracuda. Others, such as the 

 herring, feed upon smaller fishes and the pelagic pteropods and 

 copepods ; and others, like the shad, upon the minute organisms 

 of the ocean, but all, with few exceptions, are carnivorous. In 

 the other great groups of marine animals we find some scaven- 

 gers, some which feed upon micro-organisms, and others which 

 hunt and destroy each other, but there is no group of marine ani- 

 mals which corresponds to the herbivora and rodents and the 

 plant-eating birds and insects of the land. 



There is so much room in the vast spaces of the ocean, and 

 so much of it is hidden, that it is only when surface animals 

 are gathered together that the abundance of marine life becomes 

 visible and impressive ; but some faint conception of the bound- 

 less wealth of the ocean may be g;ained by observing the quick- 

 ness with which marine animals become crowded together at the 

 surface in favorable weather. On a cruise of more than two 

 weeks along the edge of the gulf stream, I was surrounded con- 

 tinually night and day by a vast army of dark brown jelly-fish, 

 (Linerges mercutia) whose dark color made them very conspic- 

 uous in the clear water. We could see them at a distance from 

 the vessel, and at noon when the sun was over head we could 

 look down to a great depth through the centre-board well, and 

 everywhere, to a depth of fifty or sixty feet, we could see them 

 drifting bv in a steady procession, like motes in a sunbeam. We 

 cruised through them for more than five hundred miles and we 

 tacked back and forth over a breadth of almost a hundred miles, 

 and found them everywhere in such 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 



