146 BACTERIOLOGY. 



forming large gelatinous masses resembling frog 

 spawn. The vegetation is so rapid that forty-nine 

 hectolitres of molasses, containing 10 per cent, of 

 sugar, were converted within twelve hours into a 

 gelatinous mass ; consequently, it is a formidable 

 enemy of the sugar manufacturers. 



Genus IV. Bacillus. 



Bacillus subtilis (Hay bacillus). Cylindrical 

 rods as much as 6 p, in length, and about three times 

 as long as broad. Single forms grow to double their 

 length, and then undergo division. They also form 

 threads which may be composed of long rods, short 

 rods, and cocci. They are motile, and provided 

 with a flagellum at each end. If the nourishing 

 medium is impoverished, the multiplication of the 

 rods by division gradually ceases, and spore forma- 

 tion commences. The rods become motionless, and 

 a dark spot is visible, either in the middle or towards 

 one end. This gradually develops into a shining 

 spore with a dark contour. The rods swell slightly 

 during this process, their contour becomes unde- 

 fined, and soon disappears entirely, so that the 

 spores are set free in about twenty- four hours. 

 The spores are 1*2 ju, long, and *6 ^ broad. They 

 develop into rods in the following way. On one 

 side of the spore a swelling appears, at the summit 

 of which an opening in the spore-membrane results, 

 and the germ escapes. This lengthens into a rod, 



