ZS 
appear ajter 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 lower 
levels. In Vierwaldstattersee (’00a) 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. Fri¢ 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 
