The universal geography : earth and its inhabitants

THE BALTIC. 23the species are found also in the Xorth Sea, so that none are here indigenous.The only differences hitherto observed between the Baltic and oceanic faunaare mere modifications caused by the local surroundings. Such slight changescannot justify the creation of Baltic species attempted by the Scandinaviannaturalists. The salt-water fish which seems to have the best claim to beregarded as a distinct Baltic species is the Giidus caUarius, or Half tens, a variety ofthe cod highly esteemed for its flavour.But if the fishes that have migrated from the Kattegat to the Baltic are offew species, they none the less abound in numbers. Thus in the Bay of Kielas many as 240,000 herrings have been taken in a day, each with at least 10,000of the little Crustacea known as the Tamora longieornis in its stomach. Hence inthe fishing season of about three weeks' duration over fifty billions of tamora havebeen devoured by a single species in a single bay of the Baltic* The OdenseFiord, penetrating from the Kattegat into the northern shores of Fyen (Fiinen),teems with excellent cod to such an extent that, for want of a market, they aresold for manure to the peasantry at two or three shillings the cartload. t Theorganisms swarming in the smallest Baltic inlet must be reckoned by millions ofbillions.The same contrast observed between the open and inland seas also existsbetween the western and eastern basins of the inland sea itself. West of Riigen,on the shores of Mecklenburg and Liibeck, the marine flora and fauna present agreat many varieties not found in the Gulf of Stettin. J The eastern basin as awhole is much less thinlv peopled than the western, a difference due to its lowertemperature and to the brackish nature of its waters, suitable neither for marinenor for fresh-water animals. The organisms that have succeeded in adapting themselvesto this medium are such as are enabled to endure the extremes of heatand cold, and which Mobius accordingly proposed to call Eurythermns. Thusthere are here found only sixty-nine species of invertebrates, or about a third ofthose that frequent the Danish waters. § Wherever the water becomes drinkablethe marine fauna disappears. The Gulfs of Bothnia and Finland areinhabited exclusively by fresh-water molluscs, and the twenty species of fisheshere found are also similar to those of the Finland and Swedish lakes. Thus theBaltic presents the curious example of a sea with two distinct faunas, one oceanic,the other lacustrine. In fact, the sea itself is of a twofold character, by its greatsouthern and western basins forming a gulf of the ocean, in its northern andeastern extremities consisting of open lakes resembling in their phenomena andproducts the waters of the surrounding mainland.* Mobius, "Expedition of the Pomerania," 1871.t Irminger, "Notice sur les peehes du Danemark," Revue maritime et eolom'ale, September, 1S63.1 " Expedition .'of the "1871.§ 216 species in the western basin; 241 in the whole Baltic (Mobius, "Expedition of the Pomerania,"1S71).u 2