366 ANIMALS IN INLAND WATERS 



America. The water which saturates the masses of peat-forming 

 mosses and their remains is rich in humic acid, the antiseptic qualities 

 of which prevent decay. Thus the dead plants accumulate on the 

 substratum. New generations of peat mosses continue to grow upon 

 these, so that finally thick layers of undecayed plant remains, from 

 which soluble materials have been extracted, are piled up, forming 

 peat, which may be 20 or more meters thick. In the beginning of peat 

 formation a shallow, flat moor is formed which is still in contact with 

 the mineral substratum from which it draws nourishment ; gradually, 

 as the layer of peat thickens, there is a transition through a "middle 

 moor" to a "high moor" in which the connection with the substratum 

 is finally entirely broken by the immense layers of peat. 



In such moors, bodies of water are formed in various ways. Peat- 

 bog ponds are sometimes the last stages of lakes and sometimes the 

 results of a sinking of parts of the moor. They are usually shallow 

 basins or even puddles. The waters laden with humus may flow out 

 of the moor, as in many mountain lakes, like the Scottish lochs, and the 

 Teufelsee in the Bohemian Forest. Wherever the peat is used as fuel 

 by man, water gathers in the cuts and ditches. The peat itself is 

 saturated with water which forms the habitat for a few types of 

 animals. 



These waters are characterized by low content of nutritive salts 

 as well as by this high humus content. They are often entirely com- 

 posed of rain-water more or less effectively shut off from the mineral 

 substratum by a so-called false bottom which may or may not occupy 

 all the space down to the true bottom. The concentration of nutritive 

 elements decreases upwards through the layers of peat. Thus the bot- 

 tom layer contains 0.25% P 5 5 and 4% CaO. The middle layer 0.2% 

 and 1%, respectively, and the top layer only 0.1% and 0.5%, re- 

 spectively. 26 In a liter of water from the Teufelsee, there is only 

 0.97 mg. of lime; the total solid residue in a liter of water is 18 mg., 

 a third of which is organic matter. 27 As far as they have been an- 

 alyzed, American bog-lakes are roughly similar as regards dissolved 

 chemicals. 



Bog waters are best characterized by their content of humus ex- 

 tracts. These consist of unchanged colloids of original plant sub- 

 stances, mixed with carbonaceous products of disintegration. It is 

 these humus substances, according to their abundance, which give the 

 characteristic yellow to brownish color, to bog and swamp waters. In 

 shallow moors a part of the humic acid is combined with lime; larger 

 amounts are present in the waters of high moors. At the surface, the 

 open waters may be fairly well aerated; the deeper waters of bogs, 





