studies of the plankton. Early reports which made important contri- 

 butions to our knowledge of the Crustacea were those of Smith (187U) 

 and Forbes (I89I) for Lake Superior, and Birge (I88I) and Forbes 

 (1882) for Lake Michigan. Other important papers of more recent 

 appearance were those of Birge (I89U) and Marsh (1895) for Lake Michigan, 

 Lake St. Clair, and Lake Erie, Pearse (1910) for the state of Michigan, 

 Sars (1915) for Geor.'^ian Bay, Bigelovj (1922) for southwestern Ontario, 

 and Eddy (1927) for Lake Michigan. Minor contributions on the subject of 

 distribution have been made by students of fish food, such as Hankinson 

 (1916), Wickliff (1920), Clemens and Bigelow (1922), and Pritchard 

 (1931). 



The rotifers of the Great Lakes have been made known largely 

 through the work of Jennings, who published a number of papers on the 

 subject. His report of 1903 refers to his earlier papers of importance. 

 Kellicott (1896 and I897) listed the rotifers of Sandusky Bay. Vorce 

 (1881 and 1882) reported a large number of organisms, both plant and 

 animal, from the Cleveland water supply. Papers on the protozoa have 

 been noted in the chapter on phytoplankton. 



Almost nothing is known of the abundance of zooplankton in the 

 Great Lakes, Whipple (1913) made some counts of Crustacea and rotifers 

 in Lake Ontario near the mouth of Genesee River, and Eddy (1927) reported 

 a few surface hauls from the southern part of Lake Michigan, Burkholder 

 and Tressler (1932) presented some data on the abundance of zooplankton 

 in four bays near the outlet of Lake Ontario, and in certain other waters 

 connected with St. Lawrence River. The most comprehensive study of the 

 abundance of plankton Crustacea in the Great Lakes is the one carried on 

 in Lake Erie in 1928, the results of which appear in a paper by 

 Wilson (1929). The value of the results is largely limited by the fact 

 that the methods employed were not strictly quantitative. 



Since the completion of the present survey, a paper on the 

 rotifers of a pond on South Bass Island has been published by 

 Ahlstrom (1933). 



Materials and methods 



This paper deals with a quantitative investigation of the 

 zooplankton of Western Lake Erj.e carried on in 1928, I929, and 1930, 

 Some work was done in each of the months of April to November, inclusive, 

 but the most complete data were obtained in June, July, August, and 

 September, The part of the paper which concerns the plankton in 1928 is 

 based on 83 series of samples taken with a closing net similar to the one 

 described by Juday (I916), With minor exceptions a series consists of two 

 hauls, one from a depth of two meters to the surface, and the second 



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