BACTERIA. 29 



division ; hence the name " Fission-Fungi " or " Fission- Algae," 

 has been applied to the Bacteria. 



SPORES. The spores are probably developed in two ways. In 

 the ENDOSPOROUS species (Figs. 28, 29), the spore arises as a new 

 cell inside the mother-cell. The spores are strongly refractile, 

 smaller than the mother-cell, and may be compared to the 

 aplanospores of other Algae. In addition to these there are the 

 ARTHROSPOROUS species in which the cells, just as in Nostoc and 

 other Blue-green Algae, assume the properties of spores without 

 previously undergoing an endogenous new construction, and are 

 able to germinate and form new vegetative generations (Fig. 27). 

 The formation of spores very often commences when the vegetative 

 development begins to be restricted. 



FIG. 27. Leuconostoc mesenterioides : a a zooglcea, natural size ; b cross section of 

 zoogloea; c filaments with spores; d mature spores; e-i successive stages of germina- 

 tion ; in e portions of the ruptured spore-wall are seen on the external side of the muci- 

 laginous covering, (b-i magnified 520.) 



The spores germinate as in JVbsfoc by the bursting of the external 

 layer of the cell-wall, either by a transverse or longitudinal cleft, 

 but always in the same way, in the same species (Fig. 28, example 

 of transverse cleft). 



DISTRIBUTION. Bacteria and their germs capable of development, 

 are found everywhere, in the air (dust), in surface water, and 

 in the superficial layers of the soil. The number varies very 

 much in accordance with the nature of the place, season, etc. 

 They enter, together with air and food, into healthy animals and 

 occur always in their alimentary tract. 



