90 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



up microscopic organisms from the water; others, such as most holothurians, eat the 

 mud of the bottom and digest out of it the foraminifera aud small mollusks and anne- 

 lids and crustacea which it contains, while others, such as the sea-urchins of the coral 

 reefs, grind away and swallow the living coral. The universal presence of a poison- 

 ing apparatus in the cudenterates shows that the food of this great and important 

 group of marine animals must consist, in the main, of animals which are able to resist 

 or to escape, and observation shows that this is true. Floating jelly-fishes and 

 siphonophores are often found fastened to the half digested carcasses of sagittas or 

 heteropods or fishes larger than their captors, and they consume enormous numbers 

 of copepods, pteropods, young fish, and pelagic larvae of all sorts. So far as we know, 

 all the sea-anemones and coral polyps and alcyonarians and hydroids are carnivorous. 

 Some of the discomedusa?, the rhizostomes, feed upon microscopic organisms, but this 

 mode of life is exceptional, and some recent observations, as yet unpublished, by Dr. 

 E. P. Bigelow, show that the food of the rhizostomes consists of copepods. 



Except for a few plant-eating fishes and mollusks and worms and echinoderms, 

 all the animals of the ocean fall into two classes, those which subsist on microscopic 

 organisms and those which prey upon each other and correspond to the rapacious 

 animals of the land. 



There is practically nothing in the ocean corresponding to the terrestrial herbi- 

 vora, and nothing like terrestrial vegetation, except the fringe of seaweeds in the 

 shallow water along the coast, and a few floating islands of algaj like the Sargasso 

 Sea. While these tracts of vegetation are pretty extensive, they are totally inade- 

 quate to support the animal life of the ocean, and as the whole animal world is 

 dependent directly or indirectly upon plants, we must ask what takes the place of 

 terrestrial vegetation? 



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

 open to our direct observation is such an inconsiderable part of the whole, that it is 

 only when great multitudes of pelagic animals are gathered together at the surface 

 that the abundance of marine life becomes visible and impressive; but some faint 

 conception of the boundless wealth of the ocean may be gained by observing the 

 quickness with which marine animals become crowded at the surface in favorable 

 weather. 



On a cruise of more than two weeks from Cape Hatteras to the Bahama Islands 

 I was surrounded continually, night and day, by a vast army of dark-brown jelly- 

 lishes (Lincryes mercutia), whose dark color made them very conspicuous in the clear 

 water. They were not densely crowded, although they were so abundant that nearly 

 every bucketful of water we dipped up contained some of them. We could see them 

 at a distance from the vessel, and at noon, when the sun was overhead, we could look 

 down into the water to a great depth through a well in the middle of the vessel where 

 the centerboard huug, and as far down as the eye could penetrate, 50 or GO feet at 

 least, we could see the brown spots drifting by like motes in the sunbeam. We 

 cruised through them for more than 500 miles, and we tacked back and forth over 

 a breadth of almost a hundred miles, and they were everywhere in equal abundance. 



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 wind- 

 row of fish half a unle wide and at least 20 miles long; but while the pigeons are 





