90 



BACTERIA 



three species, as already stated (p. 87), 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. 



But this mode of nutrition is rare among the Bacteria : 

 nearly all of those to which reference has been made are 



Fig, 18. — Spore-formation in ^aciV/wj^. (From Klein. ) 



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 

 forms, such as Bacterium termo and species of Bacillus, 

 Vibrio, &c., will, however, flourish in Pasteur's solution, in 

 which they obtain their nitrogen in the form of ammonium 



