SPIEILLA 



659 



of which gives a new flagellum to each. Their flagella are so minute 

 as to be among the most ' difficult ' of all microscopic objects, their 

 diameter being calculated from 200 measurements by Dallinger 

 at no more than ^Tfo\uro* n f an inch. 1 Although this species does 

 not ordinarily multiply in any other way than by transverse sub- 

 division, yet, under ' cultivation ' at a temperature of 86 Fahr., its 

 cells have been seen to elongate themselves into motionless rods, 

 resembling those of Bacilli, whose endoplasm breaks up into separate 

 particles that are set free as smajl bright almost spherical spores, 

 which sometimes congregate so as to form a zooglcea-\m. These 

 germinate into short slender rods, which are at first motionless, but 

 soon undergo transverse fission, and then acquire flagella. 2 



The Vibriones may be represented by V. rugula, seen in fig. 494. 

 They are slightly curved rods and threads, from 6/n to 1 6/u long, and 

 varying in thickness from 0'5/u to 2^u. They have well-marked flagella, 

 one at each end. They appeal* in vegetable infusions, causing fer- 

 mentation of cellulose. 



The Spirilla are the largest forms in the group, characterised b} 



FIG. 495. A, Spirillum unduhi, showing flagellum at each end. Magnified 3,000 

 diameters. B, Spirillum volutans. Magnified 2,000 diameters. (Dallinger.) 



their spirally formed cells and their graceful spiral motion. They 

 are fairly represented in fig. 495 by Spirillum undula (A) and 

 Spirillum volutans (B). The threads of the former are from 1'lw to 

 1'4/u in thickness, and from 9/z to 12/* in length. They are intensely 

 active, and possess a flagellum at either end. They are found iii 

 varying decomposing infusions. 



Spirillum volutans was known to and named by Ehrenberg. It 

 is from l'5/i to 2'3/z in thickness, and varies from 25/i to 30/z or 

 more in length. It has distinctly granular contents, and a very 

 easily demonstrable flagellum at each end of the spiral ; a fla- 

 gellum was distinctly suggested by Ehrenberg on account of the vor- 

 tical action visible in the fluid before this spirillum as it advanced. 



With the beautifully corrected 6mm. power of Zeiss (apochromatic 

 dry N. A. 0'95), all but the most difficult of these can be seen in fresh 

 specimens with relative ease on a dark ground with a 12 or 18 eye- 

 piece, provided they be examined alive with the flagella in motion. 



1 Journ. of Roy. Micrmc. Soc. vol. i. (1878), p. 175, 



2 Ewart, loc. cit. 

 u u 2 



