The Relation of Mollusks to Fish in Oneida Lake 313 
VIII. Provisional quantitative studies on the amount of 
mollusk food present in the lake were made by counting the 
number of individuals in a unit area about one foot square. 
The number ranged from 4 to 163. In the thick vegetation 
in the outlet to the Oneida River an area of fifty-five acres 
was estimated to contain 435 million individuals of the small 
snail Bythina tentaculata, which is eaten by the Pumpkin- 
seed and possibly by other fishes. 
IX. The layer of dead organic matter covering the bot- 
tom, described by Petersen as the dust-fine detritus, is 
believed to furnish food for a number of mollusks, and pos- 
sibly some fish (see Forbes, 1888, b, p. 491, mud-eaters) 
such as Pumpkinseed, suckers and catfishes, which are bot- 
tom feeders. This material is said by Petersen (1911, p. 
27) to form a large proportion of the organic substance held 
in suspension in the water and is probably used, together 
with the protophyta, to a greater extent than the animal 
plankton by the pelecypods or clams. Its use by some snails 
and other animals cannot be doubted. 
CoNCLUSIONS., 
The point which stands out clearly, after completing the 
studies outlined in the previous pages, is that to understand 
the fish life of any body of water it is absolutely necessary 
to know the entire fauna and flora of this body of water and 
the relation of the biota to the fish under investigation. 
This point of view was clearly indicated by Forbes over 
thirty-five years ago (1880, p. 18) when he stated that 
‘““ Nowhere can one see more clearly illustrated what may 
be called the sensibility of such an organic complex — 
expressed by the fact that whatever effects any species 
belonging to it, must speedily have its influence of some sort 
upon the whole assemblage. He will thus be made to see 
the impossibility of studying any form successfully out of 
relation to the other forms — the necessity for taking a com- 
prehensive survey of the whole as a condition to a satis- 
