* 
[29] THE OYSTER AND OYSTER-CULTURE. relat 
quantity of oxygen and food in the water brought to it than it will in 
an interior sea, where the water is in less regular motion. These chemi- 
cal and physical differences between the North and East Seas render it 
not only impossible for the oyster to live in the latter, but also for many 
other North Sea animals, of which I will mention only the lobster, the 
larger punger (Platycarcinus pagurus), and the edible sea-urchin (Echinus 
esculentus). 
If nothing further were necessary in order to establish a permanent 
settlement of oysters in the Baltic than to plant there several thousand 
fresh and healthy mature oysters, why then cannot lobsters, crabs, sea- 
urchins, and all the other animals which are found associated with the 
oysters upon the banks, and indeed the entire fauna of the North Sea 
oyster-banks, flourish in the Baltic? If this could have been accom- 
plished, I should long ago have had a large number of the animals of 
the North Sea naturalized in the Bayof Kiel, in order to facilitate my 
own investigations, and for the purpose of instruction to students. 
Nature has already made frequent efforts to introduce not only oysters, 
but other North Sea animals, into the Baltic. Nearly every year fish 
and other animals from the North Sea appear in the Baltic, but they 
are not permanent, and soon disappear again from our fauna. 
The great storm-flood of the 13th and 14th of November, 1872, brought 
Noctiluca scintillans from the North Sea into the harbor of Kiel in such 
numbers that for weeks they made the waters of the harbor brilliant 
with their phosphorescent flashes, but very soon they had entirely dis- 
appeared. Under the present geognostic and physical conditions the 
oyster can advance no farther towards the Baltic than into the south- 
western part of the Cattegat. Here a line drawn from Samsde over the 
island of Anholt to Gothenburg represents the limits of those conditions 
suited to-their welfare. Along this extreme border of their existence one 
could not expect such productiveness and size among the oysters as a 
costly artificial system of breeding would demand in order to be profit- 
able. 
Every change in the saltness of the water below the general mean, or 
in the temperature of the sea-water, would incur heavy loss to any arti- 
ficially conducted system of oyster-breeding which might be carried on 
here. That oysters of their own accord spread out from their great 
breeding home in the North Sea into all places where they find the ex- 
ternal conditions favorable, is proven by their substantial immigration 
into Lim Fiord, in the north of Jutland. This fiord, up to the year 1825, 
consisted of a number of connected brackish-water lakes, with an eastern 
out-flow into the Cattegat. During the last century futile efforts were 
made to establish oyster-beds in these seas; but on the 3d of February, 
1825, a fearful storm-flood broke through the dam which separated the 
western portion of the Lim Iiord from the North Sea, and after this the 
water of the fiord became more salt every year, the brackish-water ani- 
