332 GENERAL SYSTEMATIC BACTERIOLOGY 



Winslow et al. (Committee Sec. Am. Bact. (1917, p. 551, 1920, p. 

 201)) give the following diagnosis: 



Monotrichic short rods capable of growing in the absence of organic matter, 

 and securing growth energy by the oxidation of hydrogen (forming water). 

 Kaserer (1905) who first described the organism states that his species will also 

 grow well on a variety of organic substances. 



The type species is Hi/drogenomonas pantotropha (Kaserer) Jensen. Nikleuski 

 (1910) described two additional species, H. vitrea and H. flava. 



The genus is included by Bergey et al. (1923, p. 31) as the first in the 

 tribe Nitrohactereae. 



Hygrocrocis. A genus of algae created by Agardh (1824). It has 

 been recognized as such by several algologists. To it were referred 

 certain bacteria by various writers. For example, one of the iron 

 bacteria {Gallionella ferruginea) was placed here by Perty (1852, p. 

 215). It is invalid as a bacterial genus. 



Valentin in 1836, p. 110, described an organism from the intestinal 

 tract of the common cockroach Blatta orientalis which he named 

 Hygrocrocis inteHtinalis. He gives the following description: "Fila 

 simplicia, tenuissima, prolonga, articulata, serpentina, apice recta, 

 moniliformia, articulis globosis. 



Leidy (1851, p. 41) states that while he was able to find many en- 

 tophytes in the intestinal tract of the cockroach, he was unable to 

 find the organism described by Valentin. Chatton and Perard (1913, 

 p. 1160) noted the name Hygrocrocis iniestinalis of Valentin. As a 

 result of a comparison of material from Blatta and that from the Julus, 

 these authors conclude that the Hygrocrocis intesiinalis of Valentin 

 and the Arthromitus cristatus of Leidy are of the same genus. They 

 accept Hygrocrocis as having priority. They describe the form as 

 follows : 



Ce sont de longs filaments k compartiments subegaux, cubiques, k croissance 

 indefinie, immobiles, et qui au surplus sont, d' apres Leidy, fixes a la parol in- 

 testinale par bouquets sur une sorte de pied commun globuleux. II y a dans les 

 T6gions sporulees de ces filaments une endospore par cellule et ces cellules pori- 

 gcnes ne sont point hypertrophiees. 



Nous ne croyons pas pouvoir attribuer au genre Hygrocrocis (Arthromitus) 

 le parasite des cobayes, qui s'en distingue par son cloisonnement tres dtroit et 

 irr^gulier, sa croissance limitee, le nombre restreint des endospores, la differen- 

 ciation des cellules qui les contienment, et enfin sa condition libre et mobile. 

 Ces caracteres seront ceux du nouveau genre Oscillospira. 



HypheothrLx. A genus of algae created by Kiitzing (1843). Some 

 of the iron bacteria have been placed here by various writers. De 

 Toni and Trevisan (1889) make it in part a synonym of Detoniella. 



