123 
Generally the fresh-water is divided into three regions, littoral 
(vadal), profundal and pelagic (limnetic). To each region corresponds 
a certain series of species. While it is possible in temperate coun- 
tries to make a good distinction between the faunas of the littoral 
and the limnetic regions, we commonly in arctic countries find as 
Wesenberg-Lund, 1908, writes, “a great mixture of littoral and pond 
forms with pelagic forms. “ 
In the preceding pages I have shown that the distribution of 
the fresh water Entomostracians depends mainly on the density of 
vegetation. In the temperate countries the shallow water near the 
beach and in the ponds is generally filled up with vegetation, while 
the deeper water is free from plants. In these countries there is a 
Sharp distinction between the faunas of the littoral and the limnetic 
regions. In arctic waters the beach and the ponds are commonly 
just as void of vegetation as the deeper water. Here there is a 
great mixture of the faunas of the two regions. This intimates 
that it is not the greater or lesser distance from the 
bo ttom or the beach but the greater or lesser density 
of vegetation on which the various faunas are de- 
pending. Thus there is no particular reason to divide the fauna 
in littoral and in limnetic species. It should rather be divided, 
according to the degree in which the species claim for vegetation, 
in phytophil and aphytophil species. 
The Distribution in other Countries of the Species 
found on Iceland. 
In Tab. 8 the procentic frequency of the occurrence of the 
species has been put down as fully as possible by means of the 
literature. 
Compared with a temperate country as Germany the Icelandic 
fauna is very poor. In Germany about 129, in Iceland only 32 
species of the Entomostracians here dealt with are found. This 
difference is surely not due to the faet alone that the climate of 
Germany is more favourable, but it is also owing to the more 
varying conditions of life in Germany. 
The following 5 species, oceurring in Iceland, are lacking in 
Germany: Lepidurus arcticus, Bosmina obtusirostris, Diaptomus mi- 
