io Biological Relation Between Bacteria and the More 



toma. He says that the beggiatoa is of great importance 

 with respect to the subject under consideration, occurring 

 in especially large quantities beneath the different sewer 

 openings, forming a slimy layer, sometimes floating in the 

 water, and covering everything along the banks. The 

 masses consist of innumerable single threads built up of 

 short members which contain numerous sulphur granules 

 in the interior of the cells. Though distributed every- 

 where the organism attained its greatest development only 

 in sewers or in grossly polluted water. The cladothrix 

 dichotoma was usually found along the banks in connec- 

 tion with the beggiatoa and in connection with the cla- 

 dothrix glornerata, in polluted water. These fission fungi 

 form the most important part of the chlorophyl-free water 

 fungi along the polluted banks. 



With regard to the algae he cannot coincide with the 

 opinion of M. von Pettenkofer, that they play an important 

 r61e in the purification of the Rhine. He states that J. 

 Ufnemann had also reached the conviction that the role of 

 the algae in the purification of rivers should not be over- 

 estimated, because it was established that the green-thread 

 algae and most of the diatoms can exist only in fresh or 

 slightly polluted water, and that their action would fail 

 where it is most desired. It is otherwise, however, with 

 the chlorophyl-free and saprophytic bacteria. The water 

 bacteria in their totality play the principle rdle in the 

 purification of rivers, as far as living organisms are con- 

 cerned. Among these the beggiatoa alba have especial 

 significance. 



In a brief report on the self-purification of streams, in 

 the Report of the Massachusetts State Board of Health for 

 1890, p. 793, it is stated that the micro-organisms which 

 were instrumental in bringing about a ten-fold reduction 

 of nitrates in the water and great changes in nitrogen 

 compounds, with almost total removal of free ammonia, 

 were " enormous growth of anabaena, synedra and zoo- 



