258 ORDER I. PSEUDOMONADALES 



times it is almost straight. A single, polar This organism has not been cultivated, 



flagellum is demonstrable; such a flagellum Source: Encountered only once in a cul- 



may occur at each end. Division of the cell ture of Oscillatoriae in water from the River 



is transverse and is preceded by a division Granta near Cambridge, England, 

 of the nucleus. Habitat: Fresh water. 



Genus IX. Selenonionas von Prowazek, 1913* 



(Von Prowazek, Cent. f. Bakt., I Abt., Orig., 70, 1913 (July), 36; Selenomastix 

 Woodcock and Lapage, Quart. Jour. Micro. Sci., S9 (N.S.), 1913 (November), 433.) 



Se.le.no. mo'nas. Gr. noun selene the moon; Gr. noun monas a unit, monad; IM.L. fem.n. 

 moon monad. 



Cells kidney- to crescent-shaped with blunt ends. Motile by means of a tuft of flagella 

 attached to the middle of the concave side. The flagella are thicker at the base than at the 

 free end and are usually about one and a half times as long as the cell. Gram-negative. 

 Anaerobic. Parasites found in the alimentary tracts of mammals, including man. 



Three species are described, and it is possible that when comparative studies are made 

 the three will be found to belong to but a single species. On the other hand it is equally pos- 

 sible that not only these three but also additional species will be recognized (Lessel and 

 Breed, Bact. Rev., 18, 1954, 167). 



The type species is Selenomonas palpitans Simons. 



Key to the species of genus Selenonionas. 



I. Found in the coeca of guinea pigs. 



1. Selenonionas palpitans. 

 II. Found in the human mouth cavity. 



2. Selenonionas sputigena. 

 III. Found in the rumen juices of ruminants. 



3. Selenomonas ruminantiuni . 



1. Selenomonas palpitans Simons, 1922. a true nucleus, dividing as the cell divides. 



(Guinea pig selenomonad, da Cunha, Brasil Boskamp {ibid., 65) was unable to deter- 



Medico, 29, 1915, 33; Selenomonas palpitans mine whether this division was mitotic or 



Simons {nomen dubium), Cent. f. Bakt., I amitotic. With Giemsa's stain the cyto- 



Abt., Orig., 57, 1921, 50; Simons, inBoskamp, plasm is blue whereas the chromatin ma- 



ibid., 88, 1922, 58.) terial, the cell membrane and the flagella 



pal 'pi. tans. L. part. adj. palpitans trem- stain red. Gram-negative, 



bling. Anaerobic (?) as presumed by Boskamp 



Description taken from Boskamp {loc. (^^^^^ ^^^^^ fron^ the fact that these 



f^'^i-)- organisms, in feces, died quickly when 



Kidney- to crescent-shaped cells with ^^^^^^^ ^^ ^j^. ^.j^^^ likewise did not grow 



blunt ends, 1.8 to 2.3 by 6.8 to 9.1 microns. ,. „ „ j-v.^^ , ^^^;„ 



' . / ,^ , a ^^ ^u aerobically on ordmary media. 



Motile by means of a tuft of flagella on the ., t^ j • xi_ c 



•' . . . ^, ,1 rru a 11 Source: Found in the cecum oi a guinea 

 concave side of the cell. The flagella are 



thicker at the base than at the free end and P*^ 



are 



usually about one to one and a half times 



Habitat : Found in the ceca of guinea pigs. 



long as the cell. A highly refractive Not found in the buccal cavity, the stomach 



granule is found on the concave side at the or the small intestine. Decrease rapidly in 



base of the tuft of flagella; this granule number in the upper large intestine and dis- 



stains with nuclear stains and appears to be appear entirely in the lower part. 



* Prepared by Mr. Erwin F. Lessel, Jr., Cornell University, Geneva, New York, January, 

 1954. 



