CONDITIONS OF LIFE OF THE FISSION FUNGI. 535 



micrococcus urese, can bear an extremely high degree of 

 alkalinity. Some bacteria show such indifference with 

 regard to the reaction of the nutrient medium that they 

 may commence their development on a markedly acid 

 soil, then convert the reaction by the products of their 

 growth into an alkaline one, and continue to grow in the 

 presence of a marked excess of alkali. 



3. Other Vital Conditions of the Bacteria. 



According to the experiments which have as yet influence of 

 been made light does not appear to be one of the 1? 

 general conditions of life of the bacteria ; the observation 

 made by Engelmann that in the case of one species 

 of bacterium (bacterium photometricum) the swarming 

 movements were dependent on the light does not 

 with certainty refer to a bacterium but more pro- 

 bably to a fission alga.* TVith regard to the injurious 

 action of sunlight, see Part 5. In like manner elec- Electricity, 

 tricity, so far as it comes into play under normal 

 conditions, is without any influence ; strong currents, 

 however, interfere with the development of the culti- 

 vations, t Alterations in the pressure are borne by Highpressur 

 many bacteria in a remarkable manner, as has been 

 shown, for example, in the case of the bacillus butyricus ; 

 Certes has also observed that putrefactive processes 

 go on even under a pressure of 350 to 500 atmo- 

 spheres, and that anthrax bacilli retain their virulence 

 after exposure for 24 hours to 600 atmospheres. 



To a certain extent rest and the absence of mechanical Mechanical 



1 /> . f .-, movement. 



movement appear to be of some importance for the 

 fission fungi, although the experiments made in this 

 respect have not given entirely uniform results. A con- 

 tinuous, gentle, flowing movement of the nutrient media 

 does not appear to hinder the development of the fission 

 fungiij: ; on the other hand, it was observed that con- 

 tinuous and marked shaking of the fluid, such as is set 



* Pfliiger's Arch., vol. 26, p. 537. Botan. Zeitfj., 1882. 

 t Cohn and Mendelssohn, Cohn's Beitrdge, vol. iii., part 1. 

 X Hoppe-Seyler, Festschrift u. s. w. "Ueber die Einwirkung des 

 Sauerstoffs auf Gahrungen," 1881. 



