380 IMPORTANT VARIETIES OF FISSION-FUNGI. 



gelatin plates show the deep colonies as yellowish, round, finely 

 granular, and sharply outlined ; the superficial are similar, but more 

 spreading, thin films. The gelatin stab culture presents a delicate 

 growth in the stab, and yellowish, abundant surface growth, with 

 gradual liquefaction and formation of an air space. No growth 

 upon potato. Nutrient fluid rapidly becomes turbid with a thick 

 pellicle. As Kutscher also remarks, Beijerinck's descriptions of three 



Fig. 19. — Spir. tenue Ehr., after Migula. 



forms of Sp. tenue (C. B. L. I, 1) are not sufficient for identification. 

 Bonhoff found one form deviating somewhat from Kutscher's descrip- 

 tion ; for example, with only two flagella on each side. 



Spirillum undula. Ehrenberg, emend. Cohn and 

 Kutscher. 



Relatively large threads; usually £ to 1, rarely 1£ to 3 turns ; 

 height and diameter of each turn, 4-5 //. After longer cultivation 

 there are often scarcely any except straight forms. With terminal 

 bunches of flagella, three to fifteen in number. In gelatin plates there 

 occurs only in the depth a slow growth of sharply outlined, finely 

 granular colonies, beneath which the gelatin sinks a little. In the 

 stab culture development takes place in the upper two-thirds of the 

 stab; the growth on the surface 1 of the gelatin is thin, whitish, slightly 

 lobulated, and after ten days sinks slowly into a depression. Grows 

 on potato. Nutrient fluids uniformly cloudy, without pellicle. 



Recently Zettnow and Kutscher have differentiated from this Spir. 

 undula minus also a Spir. undula majus, which is about one-third 

 larger and grows well on meat-infusion gelatin and agar ( C. B. XVIII, 

 614; xix, 393). 



Spirillum volutans. Ehrenberg, emend. Cohn and 

 Kutscher. 



Not only the largest spirillum, but one of the largest varieties of 

 bacteria. The threads are about 2-3 fj- thick and spirally wound, the 

 height of a turn being 6.6 fi, length 13.2 /*; usually there are 21 to 3| 

 turns. In cultures the forms are smaller, similar to the Spir. rubrum. 

 According to Cohn, they have one large flagellum at each end ; accord- 

 ing to A. Fischer and Kutscher, a terminal tuft of three to eight long 

 flagella, which are often plaited together. The colonies in gelatin 

 plates at first resemble those of Bact. coli; later the gelatin sinks in, 

 and the peripheral parts of the colonies break up. Agar plates are 



