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consequently, cannot take place. Danmnevig, now, is of opinion, thas he has 
observed in his salt-water reservoirs, that the colour of the cod remains 
unchanged, even for several years, both that of the red and that of the 
grey cod; but he ends nevertheless by saying: "There is another way to 
the goal, which is both shorter and safer.” — '"What is more reasonable 
then, than that he provides himself with a light, grey deep-sea cod and a 
red ""Taretorsk”, and then changes the colour of the former into red, that 
of the latter into grey?” 
I must acknowledge that Dannevig is right here. This is the safest way to 
solve the question. As the experiment, as far as I know, has not been made 
before, and as I had just in the Great Belt great facilities for getting cod 
of a very red colour, at Refsnæs, out on the algæ-bottom, I took, on the 
25th of May 1900, a number of these red cod on board, and kept them 
alive in a tank with fresh-streaming water till our arrival at Korshavn at 
Fyens Hoved. Here half a score of them were placed in a cod-trap, the 
entrance of which was closed, on a greyish zostera-bottom. They were left 
quite to themselves till 1. June. The trap was then taken out of the water, 
and all the cod were now grey, so that nobody who had not seen them 
before, would have observed anything particular in their colour. On the 
border of the lips and on the fins, however, some had still a faint reddish 
tinge. That also this would have quite disappeared at last, there is no 
doubt. The experiment has afterwards been repeated in the tanks of the 
Biological Station. There we kept red cod for a somewhat longer time, 
and at last every tinge of red disappeared from them. Of course, we might 
as well have made grey cod red, by removing them to a red bottom; but, 
partly, this is not so easy to do, as the red bottom is to he found only 
here and there on deeper places with many currents, so that it is no easy 
matter to place a trap in the water, partly, I consider it to be quite super- 
flaous — and so does Dr. Hjort — especially now after the above experi- 
ment has been made, with the most extreme differences in colour, because 
such changes of colour in fish is a thing everybody who works with living 
fish has often the opportunity of seeing, and they are easy to understand 
when you know the histology of the skin. The red, yellow, and black 
colour-cells are always there, and the changes of colour only depend on, 
whether the cells are more or less contracted. They may be contracted into 
quite small round points, whereby the corresponding colour almost dis- 
appears; particularly when, at the same time, the cells of another colour 
have sent out their ramifications, so that these cells, branching forth in the 
form of a star, spread their bodies, and thereby their colour, over a pro- 
portionally large area. All this may easily be seen, on every cod, by means 
of a strong microscope; Dannevig, however, mentions also another so-called 
race-character, which is independent of difference in colour, viz., the different 
lengths of the shore-cod and of the North Sea cod, when they become ripe 
EET NEN 
