Gladocera of Wisconsin and Europe Compared. 285 
of that sort I have no doubt that the number of the species of 
that genus which are found in temporary pools is smaller here 
than in Europe, as the rainfall here is so much less. Sars, 
who has described so many species of Daphnia , reduces the 
total number for Norway to nine in his latest list. My list in¬ 
cludes eleven species and varieties of this genus, and the num¬ 
ber should be reduced about one-half in order to compare it 
fairly with Sars’ list. 
Norway on the other hand furnishes fifteen species of the 
genus Bosmina. This genus has yielded me only four species. 
I have a large amount of material, embracing certainly several 
species, but in the absence of recognizable descriptions and fig¬ 
ures of European forms, I hesitate to describe them. Sars also 
enumerates eight species of Polyphemidse, which family in Nor¬ 
way shows marine as well as fresh-water species. If we omit 
these two families from the comparison between Norway and 
Wisconsin, we shall find for Wisconsin eighty-one species and 
varieties arid for Norway eighty-two species. If we take 
from Wisconsin’s list the varieties of the genus Daphnia , we 
shall be able to compare the lists on a fair basis and may 
reckon the number of the known species at about seventy-six. 
This number is so nearly equal to that found in Norway, whose 
Cladocera are better known than those of any other European coun¬ 
try, that it seems fair to compare the fauna of Wisconsin with that 
of Europe in order to see how many species are common to both 
sides of the Atlantic and how many are peculiar to America. 
The following table shows these relations as I find them. 
Column I shows the species common to Wisconsin and Europe, 
II the species peculiar to America, and III the varieties peculiar 
to America: 
