NATURE OF GENERIC FORMS 



89 



The conditions of life of Bacteria are very various. Some 

 live in water such as that of stagnant ponds, and of these 

 three species as already stated (p. 86), contain chlorophyll. 

 The nutrition of such forms must obviously be holophytic, 

 and in the case of Bacterium chlorinum the giving off of 

 oxygen in sunlight has actually been proved. 



FIG. 19. Spore-formation in Bacillus. (From Klein.) 



But this mode of nutrition is rare among the Bacteria : 

 nearly all of those to which reference has been made are 

 saprophytes, that is, live upon decomposing animal and 

 vegetable matters. They are, in fact, nourished in precisely 

 the same way as Heteromita (see p. 37). Many of these 



