58 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
and a rope fastened through the loops of the wires. For taking soil samples an 
instrument was made after drawings in Delbecque, “ Les Lacs Francais” (fig. A). 
This gave satisfaction in soft bottom, but when the clay was stiff, or mixed with 
coarse sand or gravel, the point was unable to penetrate. These samples were sent 
to the Division of Soils, United States Department of Agriculture, for analysis. 
DEPENDENCE OF FISHES UPON PLANT LIFE. 
It is needless to go into the statistics of the value of the fish industry. The 
fresh-water fisheries alone amount to more than $4,000,000 annually, not to mention 
the capital invested in trout, bass, and other game fish. The importance of the 
subject from an economic point of view fully warrants an exhaustive study of tin 
A. Soil sampler, after B. The grapple. 
Delbecque. 
conditions of fish life and a thorough understanding of their food supply. As has 
been pointed out by both Reighard ' and Ward, 2 a complete knowledge of the life of 
a fish can only be obtained by a study of the entire chain of biological relations 
existing in lakes and streams. In this chain plant life constitutes an important link. 
Plants stand between animal life and the inorganic substances it is unable to use. 
All aquatic animal life is ultimately dependent upon plants, which transform carbon, 
nitrogen, and other inorganic substances into organic compounds fitted for animal 
use. Directly or indirectly, then, plant life is necessary to the support of the fishes 
1 Loe. cit. 
2 Ward, H. B. A Biological Examination of Lake Michigan. Bull. Michigan Fish Commission No. 6, 1896. 
