OF ANIMALCULES. 69 



weather they are very abundant : lengtli, l-3600th of an 

 inch. They require a much greater magnifying power 

 than the last, owing to the small diameter of their body. 



99. Vibrio bacillus:^ The stick Vibrio, — This species 

 is rather shorter than the V. rugula, and each extre- 

 mity is abruptly truncated : it is of equal diameter 

 throughout its length. Its motion is languid. Muller 

 found them in an infusion of chopped hay, while in a 

 similar infusion made at the same time, in which the 

 hay was not cut, he found only the Monas atomas and the 

 Kolpoda cucullus. 



100. Vibrio spirillum {Spirillum volutans, E.) The 

 screw Vibrio. — This interesting microscopic object varies 

 from about l-2000th to 1-1 000th of an inch in length: 

 its form, although simple, is remarkably singular ; like a 

 slender wire formed into an helical volute, as shewn, 

 magnified, in group AQ. The coils are inflexible, and do 

 not alter during the animal's propulsion, which it accom- 

 plishes by winding itself spirally through the water, its 

 extremities vibrating slightly. In some specimens the 

 coils are very close, like the thread of a fine screw ; in 

 others, they are more open and separate. The number 

 of coils varies from two to twenty, or more. 



This singular little animalcule forms an excellent illus- 

 tration of the want of a work like the present for general 

 reference, it having been within a few years observed by 

 several individuals, each supposing it a new discovery, 

 as no English book contains the slightest sketch of it. 



