I9IS.] SCHUCHERT— BLACK SHALE DEPOSITION. 265 



pens occasionally that the animals all die at this time by suffocation 

 through want of oxygen or by sulphur poisoning."^ 



Johnstone* states that " In some parts of the sea, as for instance 

 in the ' dead grounds ' of the [very shallow] Bay of Kiel, in some 

 parts of the Black Sea, and perhaps in parts of some of the Nor- 

 wegian fjords, where the water circulation is defective, and where 

 there may be a deficiency of oxygen, very remarkable bacteria are 

 to be found. These are the sulphur bacteria, the occurrence of 

 which is not, however, confined to these habitats. In the places I 

 have mentioned sulphuretted hydrogen is evolved from the decom- 

 position of dead organic matter, and this sulphuretted hydrogen, 

 to us a vilely smelling and poisonous gas, is utilized as food sub- 

 stance by the bacteria. Such a microbe as Beggiatoa takes in the 

 SH, and oxidizes it so that the sulphur is deposited in the cells of 

 the bacterial colony, and the hydrogen appears as water. This is 

 the form of assimilation of the organisms. Then some of the sul- 

 phur thus resulting from the decomposition of the SH, is oxidized 

 to sulphuric acid. This is the form of respiration of the organism. 

 It requires some source of nitrogen for the formation of its living 

 proteid and this it obtains from the minute quantities of nitrates 

 and nitrites which exist in solution in the water in which it lives. 

 But it requires very little nitrogen compound, for whereas a higher 

 animal may require to oxidize some of the living nitrogenous tissue 

 of its own body in order to obtain its energy, the sulphur bacterium 

 oxidizes the sulphur stored in its cells as the result of the assimi- 

 lation of the SH2. Thus the proteid part of the cell is protected 

 from waste, and the minimal quantity of nitrogenous food-stuff 

 suffices." 



Kriimmel states that the troughs of the Baltic Sea renew their 

 deeper water irregularly and periodically. In the Riigen and Born- 

 holm troughs (about 325 feet deep) the renewal takes place at 

 least once and more rarely twice each year, in the Danzig trough 

 (about 325 feet deep) nearly every year, and in the deeps off Got- 

 land and in the Gulf of Bothnia usually only after many years. 

 All these troughs get the new deeper water from the western Belt 

 Sea and more rarely also from the Oresund east of Denmark. 



" Sir John Murray, " The Depths of the Ocean," 1912, pp. 257-258. 

 * " Conditions of Life in the Sea," 1909, p. 264. 



PROC. AMER. PHIL. SOC, LIV. 2l8 R, PRINTED AUG. 24, I915. 



