438 ‘ Miscellaneous. 
peared in English. I send it to you as being likely to interest — 
naturalists in this country. E 
35 Royal Terrace, Edinburgh. I am, yours faithfully, . 
April 22, 1864. Rosert B. Watson, — 
‘fe 
of Christiansund, in Norway, by G. O. Sars, son of Professor Sars. — 
The loch is fed from a peat-moss. In the deeper parts of the loch — 
were found great numbers of Diaptomus Castor, of a blue colour, — 
along with Daphnella brachyura, Polyphemus Pediculus, and a spe- 
cies of Bosmina (B. obtusirostris). Near the shore, among grass 
and Nympheas, were Sida ecrystallina and two Lynceides, with 
numerous examples of Acantholeberis curvirostris. : 
He then says that from the deepest part of the loch he got wu 
some of the mud, and adds, “I found this, to my astonishment, ft 
of a small red Copepode, in which I at once recognized the salt-water — 
species Harpacticus chelifer described by Lilljeborg. The presence — 
of this Copepode was so unexpected that, in spite of the freshwater 
forms which I had found, I was obliged to satisfy myself by tasting 
the water, to be sure it was not brackish. It was perfectly fresh — 
and pleasant to the taste. 
«* We thus have here, though on a different scale, an interesting 
analogy to what has quite recently been observed in some of the 
great inland lakes, such as the Venern and Vettern*, in Sweden,— 
viz. that true inhabitants of the sea can, in certain circumstances, 
gradually accustom themselves to live in thoroughly fresh water. 
Here, however, the agency of change has not been great, alterations 
of physical conditions operating throughout thousands of years. The 
time in this instance has been much shorter. Apparently some very 
high flood or a furious storm from the west has driven the sea up 
on some occasion into the loch, which lies close to the coast. Other 
salt-water species have probably been carried into the loch at the 
same time, and perished by degrees as the water lost its saltness, 
while this little Copepode alone was able to survive after every trace 
of salt had disappeared. It is also interesting to observe the in- 
fluence which its residence in a foreign medium has had on its mode 
of life. While, in ordinary circumstances, it is almost exclusively to” 
be found in the very shallowest pools, I found it here, as I have 
said, in the deepest part of the water, sunk in the mud; and the 
same is the case with many of the salt-water forms found in the in- 
land lakes of Sweden (such as Idothea entomon, Gammarus loricatus, 
Pontoporeia affinis). This fact seems to indicate a certain tendency 
in these forms, when cut off from their proper habitat, to keep 
themselves isolated from the true freshwater Crustaceans.” 5 
Further on, in dredging the Mjésen Lake, one of the very largest — 
in Norway, through which flows an immense river, he says :— % 
«But my most interesting discovery here was a Crustacean whichis 
The dredgings were made in a little freshwater loch in the island 
* See Lovén, on certain Crustaceans found in the Lakes Venern and — 
Jette, ‘Ofversigt af Vetenskabens Akademiens Forhandlingar’ for — 
861, fn 
