LIMNOLOGICAL PROBLEMS 
431 
scarcely increased our knowledge with regard to the life of higher 
plants, water-insects, and almost the whole organic life of the littoral 
zone. Even in regard to the plankton it is strange to note how few 
really new facts with regard to the individual plankton, animal or plant, 
the biological laboratories have brought to light. These principally 
deal with the biology of plankton diatoms and plankton Myxophyceae. 
The main reason is, that many of the laboratories are bound by 
obligations to the fishery, which in my opinion neither promotes the 
fishery nor the limnology ; but also, partly, that the studies as 
mentioned above have been carried out on far too wide a base. It 
must be admitted that this method, when the biological stations 
began their work, was tempting and perhaps also necessary. Now- 
adays, it must be demanded from the laboratories, that regular study 
of the single 07ganism on the spot where it lives and where it groics 
is in future one of their chief tasks. Situated in nature itself, the 
laboratories have the great advantage of never wanting material, as 
also that the organisms can be studied at the very place to which 
they primarily belong. It is in nature itself that the investigations 
of the fresh-water laboratories should be carried out, and the 
investigators rnitst learn to transfer the experimental work and the 
biological observations from the aquaria to 7iatiire itself By means 
of juarked animals and plants, studied at regular short intervals the 
whole year round, this is very well possible. In my opinian, it is 
from such studies that these laboratories will be able to increase our 
knowledge of the biology of the fresh-water fauna and flora in a 
very high degree. Studies of this kind have hitherto been carried 
on only with regard to the plankton — in general for the whole 
plankton conmiunity at once, and only very rarely for a single 
plankton organism. 
When similar investigations on the same or other organisms are 
carried on in other latitudes, we will gradually get the biology of the 
species elucidated, not only at the different seasons of the year, but 
also at the different localities. Then, by and by, the material will be 
brought together on the basis of which we shall be able to build up 
what in the infancy of the science of linniology could of course only 
vainly be attempted. 
If the investigations are carried out as now^ sketched, it will be 
understood that a very great deal of the time of the investigators will 
be spent on excursions. From the explorations in nature, questions 
arise which can only be solved either by histological or by detailed 
anatomical investigations, or, if they belong to the vast field of 
heredity, by cultivation and experiment carried on for a long time 
under special conditions. For all these studies our investigators will 
hardly find sufficient time ; nor do they in reality belong to the main 
