54 CLASSIFICATION OF BACTERIA 



as green, blue, purple, brown, etc. In some cases a non-diffusible 

 yellow pigment is formed. Many yellow species are plant parasites. 



Genus l.Psewl onion as. Characters, those of family. Type 

 species, Px. aerugitwsa (Schroeter) Frost? 



FAMILY III. Spirillacece. Cells elongate, more or less spirally 

 curved. Cell division always transverse, never longitudinal. Cells 

 non-flexuous. Usually without endospores. As a rule motile by 

 means of polar flagella, sometimes non-motile. Typically water 

 forms, though some species are intestinal parasites. 



Genus \. Vibrio. Cells short bent rods, rigid, single, or united 

 into spirals. Motile by means of a single (rarely two or three) polar 

 flagellum which is usually relatively short. Many species liquefy 

 gelatin and are active animonifiers. Aerobic and anaerobic. No 

 endospores. Usually Gram-negative. Water forms, a few parasites. 

 Type species, V. comma (Koch 1884) Schroeter 1886. 



Genus 2. Spirillum. Cells, rigid rods of various thicknesses, 

 length, and pitch of the spiral, forming either long screws or portions 

 of a turn. Usually motile by means of a tuft of polar flagella (5 

 to 20) which are mostly half circular, rarely wavy-bent. These 

 flagella occur on one or both poles; their number varies greatly and 

 difficult to determine; since in stained preparations several are 

 often united into a common strand. Endospore formation has been 

 reported in some species. Habitat : water or putrid infusions. Type 

 species, S. undula (Mueller 1786) Ehrenberg. 



FAMILY IV. Coccaceoe. Cells in their free conditions, spherical; 

 during division somewhat elliptical. Division in one, two, or three 

 planes. If the cells remain in contact after division they are fre- 

 quently flattened in the plane of division and form chains, packets, 

 or irregular masses. Motility rare. Endospores absent. Metab- 

 olism complex, usually involving the utilization of amino-acids 

 or carbohydrates. Pigment often produced. 



Tribe A. Neisserece. Strict parasites, failing to grow or growing 

 very poorly on artificial media. Cells normally in pairs. Gram- 

 negative. Growth fairly abundant on serum media. 



Genus l.Neisseria. Characters, those of tribe. Type species, 

 N. gonorrhoeas Trevisan. 



Tribe 'B. Streptococcece. Parasites (thriving only or best on 

 or in the animal body) except genus Leuconostoc. Grow well under 

 anaerobic conditions. Many forms grow with difficulty on serum- 

 free media, none very abundantly. Planes of fission usually parallel 

 producing pairs, or short, or long chains, never packets. Generally 

 stain by Gram. Produce acid but no gas in glucose and generally in 

 lactose broth. Pigment, if any, white or orange. 



Genus 2. Diplococcus. Parasites, growing poorly, or not at all, 

 on artificial media. Cells usually in pairs of somewhat elongated 

 cells, often capsulated, sometimes in chains. Gram-positive. Fer- 



