SPIRILLACEAE AND NITROBACTERIACEAE 179 



merits, the rotation of which gives the appearance of sinuous 

 motion, this character indicating transition to the spiral bacteria. 

 Zopf (1885, p. 61) definitely designates the genus as spiral. 

 Some authors retained the older idea of the genus, and intro- 

 duced new generic names as Pacinia and Microspira, others used 

 the generic name Vibrio for short spirals. The latter conception ^ 

 is held by Loeffler, Fischer, Lehmann and E. F. Smith and is 

 the one adopted here. 



Vuillemin (1913, p. 518) concludes that Vibrio used as a 

 generic name should be suppressed because of its varied mean- 

 ings. He would use the generic name Microspira. However, 

 if Vibrio should be abandoned, Pacinia Trevisan would defi- 

 nitely have priority. 



Genus 2. Spirillum Ehrenberg 1830, p. 38 emended, Migula, 



1894, p. 237. 



Synonym : 



Spirosoma Migula, 1894, p. 237 

 Cells definitely spiral, not enlarged at center, motile by means of 

 5 to 20 polar flagella, or non-motile. Not readily cidiivated in 

 ordinary culture media. 



The type species is Spirillum undula (Miiller) Ehrenberg. 



Genus 3. Paraspirillum Dobell 1911, p. 99 



Cells spiral or S shaped, like spirilla, variable in thickness, ivith 

 a well marked thickening toward middle of the body, and tapering 

 toward the ends, a much elongated and spirally twisted spindle. 

 Motile by means of flagella. 



The type species is Paraspirillum vejdovskii Dobell. 



Family IV. Nitrobacteriaceae Fam. nov. 



Cells spherical or rod shaped, 7notile or non-motile, not growing 

 on ordinary laboratory media in the presence of organic matter. 

 Securing growth energy primarily by the oxidation of ammonia 

 to nitrites or of nitrites to nitrates. 



The genera may be differentiated by the following key: 



