BACILLUS MEGATERIUM. 407 



influences which favours the maintenance of the species, 

 and more especially a resistance against the effect of 

 drying ; and secondly, the fact that these cells do not 

 multiply, but can give rise to an organism resembling 

 the mother organism. These two requirements are 

 completely fulfilled in the case of the round cells of 

 bacterium Zopfii, and hence we have in this case un- 

 doubtedly a spore formation which only differs from the 

 other spore forms as yet known in that the resistant 

 properties depend less on a thickening of the cell con- 

 tents than, probably, on an alteration of the cell mem- 

 brane. 



These bacilli grow well on nutrient jelly (2 per cent. Cultivations, 

 meat extract and 2J per cent, gelatine). After 24 

 hours a thick, whitish-yellow layer is formed along the 

 line of inoculation, and in the course of the following 

 24 hours white anastomosing lines develop, and pro- 

 ject from the original line in radiating directions, so 

 that the appearance of the colony when looked at super- 

 ficially is that of the mycelium of a fungus. The 

 growth, however, only occurs on or under the surface, 

 and never extends above it; on the other hand 

 the organism requires a large amount of oxygen, and 

 does not grow therefore in the deeper layers of the 

 gelatine. No growth occurs on blood serum ; a diffuse 

 turbidity occurs at first in a 2 per cent, solution of 

 meat extract, and later a thick, whitish deposit is 

 formed at the bottom. The optimum of temperature 

 seems to be about 20 C. ; the swarming movements 

 of the rods cease at from 33 to 37 C. ; from 

 37 to 40 C. involution forms appear, and when this 

 temperature is continued for some time the bacilli lose 

 their vitality. Experiments on animals show that the 

 bacilli are harmless saprophytes. 



Bacillus megaterium (de Bary). 



janism was first observed by d 



Dage leaves. It presents the fo 



2'5 p.. in thickness, and cylindrical inform, with rounded 



This organism was first observed by de Bary on Morphological 

 boiled cabbage leaves. It presents the form of rods c aracters - 



