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 Polyphemidae, 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 and 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: 



