viii.] Aquatic Saprophytes. Beggiatoa. 81 



The species of Beggiatoa are said to have the peculiar power 

 of reducing the sulphates contained in the waters which they 

 inhabit, especially sodium sulphate and gypsum, setting free the 

 sulphur and sulphuretted hydrogen. That the living protoplasm 

 is the seat of this process is shown by the appearance in it 

 of the sulphur-grains. The form- 

 ation of sulphuretted hydrogen 

 causes first the precipitation of iron 

 sulphide in the slime inhabited 

 by Beggiatoa, which is thereby 

 turned black, and then the presence 

 of sulphuretted hydrogen, either 

 dissolved in the water or set 

 free by evaporation, gives rise to 

 the well - known odour, and may 

 have a noxious effect on the 

 animals inhabiting the water. The 

 ' white ' ground in the Bay of Kiel, 

 for example, covered by species 

 of Beggiatoa, is also called the 

 ' dead ' ground, because it is 

 avoided by fishes, though not by 

 all animals (37). These plants 

 therefore play a peculiar and 

 important part in the economy of Fi S- 7- 



nature and of mankind. According to the statements of some 



Fig. 7. Beggiatoa alba, Vaucher. a portion of a stout living filament. 

 b fragment of the same after treatment with alcoholic solution of iodine show- 

 ing the segmentation into cells, c a very thin living filament from the same 

 preparation as a. d motile spiral form (Ophidomonas). e-h formation of 

 spores ('Cocci') by successive division of the segment-cells of a stout filament 

 (e). The lumen of each spore is nearly filled up by a grain of sulphur. Inf 

 the division has advanced further than in e. g breaking up of the filament 

 into groups of spores, h the spores isolated. *, k spores appearing to 

 germinate ( ), in a state of motion, a-c magn. 600 times, but drawn a 

 little too large, </ 540 times, e-k 900 times, d-k after Zopf. 



