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is indeed not far from Oddesund; the poverty is in fact only characteristic of 
strictly limited localities just with this stony ground. On closer examination of 
the oysters dredged up I noticed that they had been much rolled about, so that 
all the small cross ,lamellæ and sharp corners usually seen on oyster shells had 
been rubbed away; the whole oyster had been rounded off like a pebble; the same 
applies to the stones in these localities. It might happen however that an oyster 
had taken up a position in a hole in a stone or in the hollow of an oyster shell, 
which was especially the case with the few younger oysters found, and these did 
not have the rounded appearance but had preserved their thin corners undamaged. 
There is only one explanation of the phenomenon, it seems to me, namely, that 
it is the motion of the waves at these places exposed to the west, which is able 
to move and roll the stones and oysters against each other during the frequent 
storms in these localities. The shells in the living oysters are thus ground down 
not only at the edges but everywhere on the outer surfaces, and although the 
øysters at these places grow very thick shells (the so-called »etage-oyster« because 
the thickness of the shells is caused by the formation of one layer of shells after 
the other), in order to counteract the grinding process, they are by no means 
comfortable here; this is noticed especially in their soft parts; these »etage oysters« 
are shunned by all oyster-eaters. The results of the gnawing of the gastropods 
above mentioned also perhaps help to make the shells rounded. 
That the strong movements of the currents on the bottom affect the young 
oysters first and chiefly is clear, as they have the weakest shells and are certainly 
very often broken in pieces during the storms, which accounts for the small 
quantities of young oysters at these places. Naturally the other animals living at 
these places which have heavy shells also bear signs of the grinding process, and 
the difference is very obvious which can be seen in a collection of oysters and 
other shellfish dredged at such localities from another dredged at a quieter spot. 
Concerning the food of the oyster, many erroneous opinions have 
held sway for long in the literature as well as with us. It was known certainly 
that the oysters must feed on quite small, almost microscopic organisms and it was 
concluded from this that they lived on the plankton, which is indeed exceedingly 
rich in the Lim Fjord. I was however much struck by the fact that I could never 
find the plankton forms in their stomachs, either of the plant or animal kingdom, 
which are so abundant in the Lim Fjord; hut only quite small, green algæ or 
diatoms which do not belong to the plankton and usually only in small quautities; 
further some sand and mud particles were often found in the alimentary tract of 
the oysters. In a »Rapport over de oorzaken van den achteruitgang in hoedanig- 
heid van de Zeeuwsche oester. ”s-Gravenhage, 1902«, new light has been thrown 
on this matter. At the instigation of the Dutch Government an enquiry was 
made into the reasons for the decrease in the oyster fisheries at several places in 
Holland; extensive observations were therefore made at various places by Dr. 
Hoek with amongst others Dr. H. C. Redeke on the biology of the oyster. 
Redeke specially studied the food of the oyster and came to the surprising but 
most probably in the main correct result, that the oyster in Holland lived almost 
