CONDITIONS OF LIFE OF THE FISSION FUNGI. 537 



The fermentative activity in all probability plays the influence of 

 same part with regard to the life of the bacteria as it tive activity, 

 does in the case of the yeast fungi. In the case of the 

 bacteria which can set up fermentation, the fermentative 

 activity appears to favour the growth of the organisms as 

 soon as a certain intensity of the fermentative action has 

 been attained, while the development of other bacteria 

 which may be present at the same time is hindered. 

 Hence a certain intensity of fermentative activity exerts 

 a marked influence on the concurrent growth of various 

 species of bacteria, and on the production of pure 

 cultivations. 



As a rule, in concurrent growth with mould and yeast Concurrent 

 fungi, the bacteria have an advantage in their ex- ^h 

 tremely rapid multiplication, and in the very energetic 

 manner in which they use up the nutrient materials. 

 It is only when some of the conditions as regards the 

 nutrient substratum are selected in such a manner that 

 they exert an unfavourable influence on the development 

 of the bacteria, while they at the same time permit the 

 unhindered growth of the other classes of fungi, that it 

 is possible for the latter to take possession of the 

 nutrient medium and to exclude the bacteria. As has 

 been mentioned, the concentration and reaction of the 

 nutrient material are the chief means by which the 

 growth of the yeast and mould fungi, as compared with 

 that of the bacteria, may be favoured. Among the 

 bacteria themselves various factors, more especially 

 reaction, temperature, relative amount of the individual 

 nutrient materials, and more especially of the nitro- 

 genous compounds, the tension of the oxygen, &c., are 

 the chief means by which one or other species may 

 succeed in growing in excess, and ultimately in almost 

 entirely gaining the upper hand. 



4. Conditions of Spore Formation and Spore 



Germination. 



To a still higher degree than the yeast fungi the Spore 

 bacteria appear able to utilise suitable nutrient materials 



