486 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [2] 



it does not appear to contain any animal life; but if it is put through a 

 fine wire sieve, which cleans out all the mud, a large number of diminu- 

 tive mollusks, worms, crustaceans, and other marine animals maybe seen. 



If we could dive down to the mud bottom without touching its sur- 

 face, we would find it full of worms, shells, and other marine animals pro- 

 truding from the mud, all busy absorbing with their mouths the parti- 

 cles of mud nearest to them ; and we would also see flounders, codfish, 

 eels, and other fish digging themselves into the soft mud for the purpose 

 of devouring its inhabitants. 



In the great depths of the Baltic, 90 to 95 fathoms, east of the island 

 of Gottland, where the bottom consists of plastic clay containing but 

 very few organic substances, I found very few worms during the sum- 

 mer of 1871. In the greatest depths of the Mediterranean southeast of 

 Sicily (1,700 fathoms), where the bottom consists of yellowish clay, the 

 British exploring expedition of 1870 found no traces of animal life. 



In the southern part of the North Sea the muddy bottoms, at a depth 

 of 20 to 25 fathoms, are literally alive with small crustaceans, worms, 

 snails, mollusks, echinoderms, and polyps, and are therefore very rich 

 in fish. 



Enormous masses of dark mud, formed from vegetable matter which 

 has sunk to the bottom, lie at the bottom of the deep fiords of Norway, 

 and furnish excellent food for their numerous fish and other marine 

 animals. 



Besides the sea- weeds, which in all latitudes grow at a depth of 25 

 fathoms on level bottoms, the sea produces different kinds of floating 

 algae, which furnish food to marine animals. 



During the summer a floating microscopic alga (Mclosira costata) ap- 

 pears in the Bay of Kiel, and probably also in other parts of the Baltic, 

 in such enormous masses that the water becomes turbid. 



Clean plates of glass which I fastened to some poles in the Bay of 

 Kiel one meter below the surface of the water were, after 8 to 14 days, 

 completely covered with diatoms, among which infusoria were crawling 

 about, the stomachs of which contained diatoms. Diatoms live in every 

 sea, and when dead form the principal component part of the finer por- 

 tions of the bottom. 



Late in summer the Baltic near the mouths of the Oder, Vistula, and 

 other rivers assumes a peculiar green color, from great masses of float- 

 ing microscopic algoe, so-called " water blossoms." The commission for 

 the scientific investigation of the German seas, which during this month 

 has examined the Bay of Danzig, on the 10th of September found a her- 

 ring-net which, east of Zoppoh, had been left at the bottom of the sea 

 for one night, covered with a greenish slime, which principally consisted 

 of such microscopic algse. 



In the Red Sea, the Atlantic, Indian, and Pacific Oceans, navigators 

 and scientists have often observed floating microscopic alga? of a reddish 

 color (Trichodesmium erythrceum) covering the sea for miles and miles. 



