SEA MUSSEL MYTILUS EDULIS. 205 



than themselves. Furthermore, animal life swarms in the sea in incredible multitudes. 

 The naturalists of the Challenger expedition reported that the waters of the equatorial 

 Pacific contained great banks of pelagic animals through which the vessel sailed. 

 Chiercha wrote that the equatorial calms of the Atlantic are rich beyond all measure 

 in animal life and that the water often looks and feels like coagulated jelly. The 

 Challenger expedition reported having encountered banks of copepods a mile thick 

 and on one occasion to have steamed for two days through a dense cloud formed of 

 a single species, one found distributed from the Arctic regions to the Equator. Brooks 

 (1893) states that he cruised for more than two weeks, from Cape Hatteras to the 

 Bahama Islands, surrounded continually, night and day, by a vast army of dark-brown 

 jelly fishes, Linerges mercutia, whose dark-brown color made them very conspicuous 

 in the clear water. They were so abundant that nearly every bucketful of water 

 dipped up contained some of them, and at noon, when the sun was overhead, they 

 could be seen through a well in the middle of the vessel drifting by at all depths down 

 to 50 or 60 feet, which was as far as sufficient light would penetrate to make them 

 visible. The area explored covered more than 50,000 square miles, in which they 

 were everywhere in equal abundance. Of the fishes Prof. Brooks says: "Herring 

 swarm like locusts and a herring bank is almost a solid wall." Goode tells of a 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 20 miles long. In the bays and 

 estuaries beds of sea mussels are often found covering hundreds of acres of bottom 

 and containing 4,000 to 6,000 bushels to the acre. 



How this vast multitude of animals can be supported in a region destitute of visible 

 vegetation has been a problem of investigation since the microscope came into use, and 

 it is interesting to note that the first contribution on the subject was written October 16, 

 1699, by the old pioneer, Antony van Leeuwenhoek, who ground lenses and made the 

 microscopes with which he opened up a new field of investigation. After observing 

 many of the minute organisms which were discovered in fresh water by means of his 

 microscope, he came to the following conclusion: 



If it be then asked, to what end such exceedingly minute animalcules were created, no answer can 

 readily be given which seems more agreeable to the truth than that, in like manner as we see constantly 

 the bigger kinds of fish feed on the smaller; as, for example, the codfish preys on the haddock and other 

 smaller kinds of fish; the haddock again on the whiting; these on still smaller fishes, and among the 

 rest on shrimps; and shrimps on still more minute fishes; and that this gradually prevails among all the 

 kinds of fish; so that, in a word, the smaller are created to be food for the larger. Again, if we consider 

 the nature of our sea, abounding with fish, yet having nothing at the bottom of it save barren sand 

 stored with various shellfish, yet destitute of every green herb; and if we, moreover, lay it down for a 

 truth that no fish can be supported on water alone, there will not remain a doubt that the smaller fishes 

 are destined by nature to be subsistence for the larger. 



It is evident from Leeuwenhoek's illustrations that his use of the expression 

 "smaller fishes" refers to what we now recognize, in general, as plankton, which in- 

 cludes both animal and vegetable organisms, particularly of the groups Protozoa and 

 Protophyta. 



Peck (1896), in his splendid paper on The Sources of Marine Food, gives us an excel- 

 lent example of the food relations described by Leeuwenhoek. Reporting on the stomach 

 contents of the squeteague, he says: 



On the morning of July 23 there was taken a large specimen whose stomach contained an adult 

 herring. In the stomach of the herring were found two young scup (besides many small Crustacea), and 

 90392°— 22 6 



