Bibliography. 
483 
see how these specific differences regularly presented themselves 
in my averages in spite of great variations in absolute numbers. 
Even those so small that they were at first supposed to be 
merely accidental recurred with great uniformity. 
In conclusion I would repeat what I said in my introduction, 
that this discussion of general causes is to be regarded as sug¬ 
gestive. I shall be quite satisfied if it indicates lines of invest¬ 
igation to students of the fresh water plankton. 
LITERATURE TO WHICH REFERENCE HAS BEEN MADE. 
Apstein, ’96. Das Siisswasserplankton. Methode und Resul- 
tate der quantitativen Untersuchungen. Carl Apstein. 
Kiel, 1896. 
Birge, ’95. Plankton Studies on Lake Mendota. I. E. A. 
Birge. Trans. Wis. Acad. Sci., Arts and Letters. Vol. 
X., pp. 421-484. 
Birge, ’97. The Vertical Distribution of the Limnetic Crustacea 
of Lake Mendota. E. A. Birge. Biol. Centralblatt, Vol. 
XVII., pp. 371-374. 1897. 
Drown, ’90. Interpretation of the Chemical Analysis of Water. 
T. M. Drown, Ph. D. Mass. State Board of Health, 22d 
Report, pp. 533-578. 1890. 
Drown, ’91. Dissolved Oxygen in Waters of Ponds and Reser¬ 
voirs at Different Depths. T. M. Drown, Ph. D. Mass. 
State Board of Health. 23d Report, pp. 353-373. 1891. 
Eigenmann, ’95. Turkey Lake as a Unit of Environment and 
the Variation of its Inhabitants. C. H. Eigenmann. 
Proc. Indiana Acad. Sci., Vol. V., pp. 204-296. 1895. 
EitzG-erald, ’95. The Temperature of Lakes. Desmond Fitz¬ 
Gerald. Trans. Am. Soc. Civil Eng. Vol. XXXIV., pp. 67- 
114. 1895. 
France, ’94. Zur Biologie des Planktons. R. H. France. Bio¬ 
log. Centralblatt, Vol. XIV., pp. 33-38. 1894. 
Fric and Vavra, ’94. Die Thierwelt des Unterpocernitzer und 
Gatterschlager Teiches. Dr. Ant. Fric und Dr. V. Vavra. 
Unters. u. d. Fauna der Gewas. Bohmens, IV. 1894. 
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