PKUTOPHYTIC AND OTHER FUNGI. 



309 



tween two cells that are separating from each other (as in Fig. 196, a, 

 #), the rupture of which gives a new flagellum to each. Two species of 

 this type, differing considerably in size, have been especially studied. 

 The cells of Bacterium ternio (Fig. 193, A), which seem to be the ( fer- 

 ment ' of ordinary putrefactive change, have a diameter of about 1-20- 

 000th of an inch, and are somewhat longer than they are broad. Their 

 flagella are so minute as to be among the most 'difficult 7 of all Micro- 

 scopic objects (p. 162); their diameter being estimated by Mr. Dallinger 

 at no more than 1-200, 000th of an inch. 1 Although this species does not 



f m, . 193 



A, Bacterium ternio, each cell furnished with a single flagellum: Magnified 4,000 diameters. 

 B, c, D, Bacterium lineola, each cell when separated having a tiagellum at either end. Magnified 

 3,000 diameters. 



ordinarily multiply in any other way than by transverse subdivision, yet, 

 under ' cultivation ' at a temperature of 86 9 Fahr., its cells have been 

 seen to elongate themselves into motionless rods, resembling those of 

 Bacilli (Plate xii.), whose endoplasm breaks up into separate particles 

 that are set free as small, bright, almost spherical spores, which some- 

 times congregate so as to form a zoogl&a-mm. These germinate into 

 short, slender rods, which are at first motionless, ,but soon undergo trans- 

 verse fission, and then acquire flagella. 2 The B. lineola, which is the 



4, Bacillus subtilis; each cell, when s^m-red, biflagellate. Magnified 4,000 diameters. B. 

 Bacillus ulna, each cell biflageliate. Magnified 3,00 j diameters. 



special < ferment ' that turns milk sour, occasioning the conversion of its 

 sugar into lactic acid, has about three times the length and diameter of 

 the preceding, and exhibits much stronger to-and-fro movements. 



306. The special peculiarity of Bacillus consists in the extension of 

 its cells into straight rods, sometimes of considerable length, which 

 break-up by transverse subdivision into separate cells, each of which has 

 a flagellum at either end, though, when the cells are paired (like those 

 of Bacteria), each carries a flagellum at its free end alone. The B. sub- 

 tilis ( Vibrio subtilis of Ehrenberg), found in stale boiled milk that is 

 undergoing the butyric fermentation, is a slender supple thread (Fig. 

 194, A), whose cells average about 1-5, 000th of an inch in length, mov- 

 ing in a ' pausing' manner, "like a fish forcing its way through reeds." 

 The B. ulna (Fig. 194, B), found by Colin in a stale infusion of boiled egg, 



1 " Journ. of Roy. Microsc. Sic. 



2 Ewart, loc. cit. 



Vol. i. (1878), p. 175. 



