4 
It was mainly an insight into the distribution of the invertebrates which 
was obtained, the larger fish could not be taken with the small apparatus used 
at that time; but the knowledge was gained from these investigations, that the 
occurrence of the lower animals is conditioned by certain laws, which produce an 
order and regularity specially evident in their bathymetric distribu- 
tion. I endeavoured to show, that knowledge of the simplest. natural conditions 
of the bottom and the waters could already for a great part explain many things 
and much in the occurrence of the animals (»General Results«) and from much 
later investigations in the same waters I have become convinced, that this order 
and regularity is not a phenomenon of short duration. The same characteristic 
occurrences are found again in the main after more than 20 years have passed, 
though I will by no means seek to deny, that a shifting, especially horizontally, 
does take place in the distribution of various species from year to year. The im- 
pression of the fauna as a whole remains however unchanged within such a short 
period of time as one generation. This holds good for the Kattegat and the 
Baltic, thus for comparatively open and large stretches of water. 
In 1890 I began my work as Director of our »Biological Station», which 
was founded in that year, and investigations of a more purely ichthyolo- 
gical nature occupied my time for a number of years thereafter. From these 
investigations I learnt, among other things, that even though individuals of a 
species may occur in a water, that does not mean necessarily, that the species 
»belongs« there or can live the whole of its life there. Many fishes cannot repro- 
duce in the enclosed waters, but nevertheless occur there year after year, either 
as young or on a longer or shorter visit; the eei, for example, is really only a 
guest in our waters, though it lives the greater part of its life here; it is »cradled« 
far away from our country. The plaice cannot spawn in our fjords hut enters 
them in search of food. I saw that, to understand the distribution of the animals 
right to the bottom, we must study the occurrence of each species through- 
out the whole of its life. This has now been done for a number of fishes, 
though for only a few of the lower animals, and interesting information has in this 
way be gained. But even with all this we are not at the end of the requirements 
of biology with regard to the investigation of the animal life of the sea; the 
question of the food of the animals especially must naturally not be ignored. 
A good deal has also been written on this subject; long lists of what has been 
found in the stomachs of various fishes have been published and time and work 
have also been devoted to the study of the food of the lower animals, especially 
in recent years; but it does not seem to me, that we have yet got to the bottom 
in these matters. 
The first time that questions of this kind came forcibly to my mind, was 
when I found, that the plaice in the western Limfjord ceased almost to grow for 
2/3rds of the year, whilst those which were transplanted from these parts into 
the central Limfjord, increased their weight within the same time by 4 to 5 times 
what it was originally. 
Many of the invertebrates on which the plaice feed are found at both 
places, so that I was obliged to believe, that it was the enormous abundance of 
the plaice in the western parts, producing the phenomenon I called »over- 
