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great seasonal polymorphism in B. cornuta near Basel. Zacharias 
(97a and ’98b) records it in the plankton of German carp ponds. 
Stenroos (’97 and’98) finds it in waters of Finland and Karelia, 
where the cornuta type is littoral, and a limnetic form, distinguished 
by him as forma vernalis, is abundant in the plankton in May. .Scour- 
field (’98) finds it common in the waters of Epping Forest, where it 
is perennial, males and ephippia appearing only in September— 
November. According to Scott (99) it appears at various seasons 
in the lochs of Scotland in both the littoral and limnetic fauna. 
Burckhardt (’00a) gives an extensive revision of the genus Bosmina, 
and includes in the B. longirostris group nine other so-called species, 
among which are B. cornuta Jur. The species is “pelagic or hemi- 
pelagic” in various Swiss lakes, though apparently not in num- 
bers. The genus is there represented in the plankton princi- 
pally by the B. coregont group. Amberg (’00) lists it from Katzen- 
see, near Zurich, as a perennial planktont with large numbers in 
May, August, and February, but gives no statistical data. Fuhr- 
mann (’00) finds Bosmina perennial in Neuenburgersee, and B. 
longirostris with a maximum in May. Marsson (’00) finds B. 
“longirostris-cornuta”’ in lakes about Berlin throughout the year, 
with larger numbers in some lakes during the warmer months and 
in others in November—December. In Barlewitzersee, near Danzig, 
Seligo (’00) reports B. cornuta as perennial, with maxima in June 
and in October-November, the latter being the greater. Larger 
numbers appear in summer than in winter. Cohn (’03), in waters 
near K6nigsberg, finds B. longirostris only sparingly present, 
appearing in May—September with a maximum in July. 
In European streams, also, B. longirostris is widely distributed. 
Lauterborn (’94) finds it abundant in the winter fauna of the Rhine. 
He also states that it is not acyclic in the backwaters, where he has 
found in three successive years both males and ephippia in May—June 
and again in November. There is thus a suggestion of a vernal and 
an autumnal pulse in these waters. Zimmer (’99) finds it through- 
out the whole year in the Oder. Schorler (’00) reports it from the 
Elbe at Dresden in May—October, with larger numbers in May—June 
and September, while Fri¢ and Vavra (’01) find it in the same 
stream near Podiebrad. They state that B. cornuta is found in 
great numbers in 1 m.—surface in summer months, and B. longiros- 
tris sparingly in the littoral fauna. Steuer (’01) finds B.‘‘longirostris- 
