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these problems? These are questions which continually occur 
to one familiar with this locality, observant of the operations 
of fishermen, and cognizant of some of the seasonal flux of 
life and matter in this water world of which fish are but a 
part. 
The plankton is an integral part of the chain of food rela- 
tions which extends from the water, with the gases, salts, and 
products of decay dissolved therein, on the one hand, to the 
fish and other vertebrates of commercial importance upon the 
other hand. The water, the carbon dioxid dissolved therein, 
the nitrogenous matters, and various salts in solution are util- 
ized either by the grosser aquatic vegetation or by the micro- 
scopic phytoplankton. In the former case the growing plants 
are rarely utilized directly as food by any aquatic animals. A 
possible exception to this statement is found in the case of the 
turtles. Fishermen are accustomed to feed these animals, 
when penned up for the market, upon “moss” or Ceratophyllum, 
though it may be that the insect larvee and mollusks found in 
the vegetation constitute the more important elements of 
the food. It is only when this growth of vegetation decays 
that it releases into the water the elements which conduce to 
its fertility. 
The phytoplankton, on the other hand, multiplies very rap- 
idly and is immediately available for the support of the micro- 
scopic animals of the zodplankton, and this, and to some ex- 
tent also the phytoplankton itself, is the immediate food of 
most young fish upon hatching and the customary food of some 
adult fishes,—such as Polyodon (Forbes, ’88, and Kofoid, 99) and 
many minnows.—of the bivalve mollusks, and of many other or- 
ganisms of sessile habit. The plankton is thus the prime source 
of food of fishes and of many other organisms utilized by’fish 
as food. The chain of food relations, for example, between 
the food elements of the water and the black bass is in the 
main a short one, with the plankton as the principal link. Pro- 
fessor Forbes (’80) has shown that 86 per cent. of the food of 
the game fish consists of other fishes, principally Dorosoma with 
