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appear after the period of maximum summer heat. Zacharias ('97a) 

 reports it from German carp ponds in July, and Stenroos ('97) lists 

 it as a littoral species in midsummer in northern Russia. Scott ( '99) 

 finds it rarely in lakes of Scotland in August, and then only in the 

 plankton, though many shore collections were examined. Burck- 

 hardt ( '00) reports it from the smaller and shallower Swiss lakes in 

 isolated records ranging from May to November, and regards its 

 absence from the deeper lakes as due to the low temperatures which 

 at all seasons would surround its winter eggs, which sink to the low r er 

 levels. In Vierwaldstattersee ('OOa) he finds this species in the 

 plankton only in September-November, and then more abundantly 

 near shore than in the middle of the lake. In Alpnachersee the 

 period of occurrence extends from June to November with a maxi- 

 mum in July. Fuhrmann ('00) gives the seasonal distribution in 

 Neuenburgersee as extending from May to November, with a maxi- 

 mum in September. Marsson ('00) finds a seasonal distribution 

 from July to October in small lakes near Berlin. Seligo ( '00) finds 

 in Hintersee, near Danzig, a seasonal distribution in 1898 extending 

 from June 6 to October 18, with a maximum of 225,000 under 

 1 sq. m., depth, 24 m. (?) on August 9. Fric and Vavra ( '01 ) state 

 that this species is very abundant in summer months in the plank- 

 ton of the backwaters of the Elbe, especially in levels at depths 

 of 0-1 meter. Cohn ('03), on the other hand, finds in waters near 

 Konigsberg that Diaphanosoma is present in greatest abundance 

 in depths of 20-30 meters. It occurs in summer months, with large 

 numbers in July-September and a maximum in August-September. 

 It was not found in shallow waters. 



As a constituent of the potamoplankton Diaphanosoma has been 

 reported by Schorler ('00) in the Elbe at Dresden as abundant in 

 June-September. Steuer ('01) finds it in the backwaters of the 

 Danube at Vienna in June-September, with a maximum in August, 

 but never in great numbers. Meissner ('03) reports it sparingly 

 from the Volga in July. 



In American waters Diaphanosoma is widely distributed. Forbes 

 ('90) found it abundant below surface levels in Lake Michigamme 

 in August. Birge ( '94) reports it in the plankton of western Lake 

 Erie but not in that of Lake St. Clair in September. In Lake 

 Mendota, Wis., he ('95 and '97) has worked out its seasonal and 

 vertical distribution with a fulness and care not equaled by any 



