1100 Proceedings of Royal Society of Edinburgh. [sess. 
had to be taken by men who had not the slightest idea of science, 
who could not be controlled at all, and of whom I had no know- 
ledge whatever. Any man may throw a net into the water, row 
about for some minutes, and put the contents in a bottle. But 
it is always a very difficult thing to base scientific results upon 
samples from deep water collected by men who are in possession 
of no scientific education, and therefore I have omitted to do so 
with regard to the present exploration. With regard to the tp., I 
have supposed that the simpler the instruments used the more correct 
would be the statements. It is proved by the plankton samples 
that all my requests have been carried out to the letter, and I wish 
to offer all, especially Mr Soemundsson, my sincerest thanks for 
the readiness with which the explorations have been established. 
As it was impossible to get samples from Greenland, it will be 
seen that I could not in this paper give as much as I had intended. 
A regular fortnightly exploration of an arctic lake will always be a 
desideratum, the lakes of Iceland having only the low summer 
tp. in common with those in arctic countries, but, on the other 
hand, never being frozen over for as long a time as the arctic 
lakes. Still, the results of my exertions are not quite fruitless, 
seeing that Thingvallavatn and Myvatn are at this moment the 
most northerly lakes in which a regular plankton exploration 
has been carried out. Further, I hope that most of the above- 
mentioned results and suppositions, already arrived at through 
explorations of the Danish lakes, have been greatly corroborated 
through this little exploration. 
In 1904 Ekman’s extremely interesting and very valuable 
paper appeared. It treated of the Crustacea fauna of North 
Swedish alpine countries, together with their arctic and sub-arctic 
life conditions. In this paper Ekman stated the existence of a 
Crustacean fauna common for the arctic region, the Scandinavian 
and the Central European alpine region ; this region he calls the 
boreo sub-glacial region. 
The Crustacea of the lowland lakes in Sweden and the Central 
European plains differ greatly from those of this region. With 
regard to the plankton Crustacea of the arctic lakes the most 
common features may be the following : the great Crustacean 
plankton of the arctic lakes is mainly composed of the following 
