Kingdom Mychota [ 27 



Family 1. Leptotrichacea [Leptotrichacei] Schroter 1886. The cells not elongated 

 in the direction of the axis of the stalk. 



Didymohelix ferruginea (Ehrenberg) Griffith (first named, and usually listed, 

 under Gallionella, which is a misspelling of the name of a genus of diatoms) occurs 

 in waters containing iron. Older authors described it as consisting of paired filaments, 

 less than 1^ in diameter, colored bright yellow with imbedded iron oxide, and coiled 

 about each other. In fact, the supposed paired filaments are the margins of a single 

 twisted band, which is not itself an organism but the stalk secreted by a terminal 

 cell. Spirophyllum Ellis is either the same species or a closely related larger one. 



Leptothrix Kiitzing Phyc. Gen. 198 ( 1843) was inadequately described; the species 

 which was first named, and which is accepted as the type, was L. ochracea. It is be- 

 lieved that this name properly designates the masses of ochraceous matter seen in 

 iron springs. Under the microscope, this matter is seen to consist of fine yellow 

 filaments, straight and unbranched. Ellis (1916) described them as consisting of a 

 cylinder of protoplasm, not divided into cells, enclosed in a sheath. Almost surely, 

 these structures, generally recognized as of the same nature as Didymohelix, are like- 

 wise stalks secreted by minute terminal cells. 



Siderocapsa Molisch and Sideromonas Cholodny, described as minute spheres or 

 rods imbedded in capsules colored by ferric oxide and attached to plants in waters 

 containing iron, are perhaps to be interpreted as stalkless members of the present 

 group. 



Nevskia Famintzin, forming minute gelatinous colonies floating on water, does not 

 accumulate iron. 



Family 2. Caulobacteriacea [Caulobacteriaceae] Henrici and Johnson 1. c. (1935). 

 The cells elongated in the direction of the long axes of the stalks. Caulobacter, Pas- 

 teuria, and Blastocaulis, colorless saprophytes in waters or parasites in aquatic 

 animacules. 



Class 2. MYXOSCHIZOMYCETES Schaffner 



Class Myxoschizomycetae Schaffner in Ohio Naturalist 9: 447 (1909). 



Class Polyyangidae Jahn Beitr. bot. Protistol. 1: 65 (1924). 



Class Spirochaetae Stanier and van Niel in Jour. Bact. 42 : 459 ( 1941 ) . 



Parasitic or saprophytic Mychota, the elongate cells with thin walls or none, 

 capable of bending movements and sluggishly or actively motile. In many examples 

 there is a resting stage: the cell contracts generally, so as to diminish the surface, 

 and deposits a definite wall. The structure so produced is a spore of the type called 

 an arthrospore or chlamydospore. 



The two orders Myxobactralea and Spirochaetalea have not previously been 

 combined to form a separate class. A certain species which Hutchinson and Clayton 

 (1919) described as a spirochaet, Spirochaeta cytophaga, has subsequently been 

 found to be a myxobacterium. The hint of relationship thus conveyed is confirmed 

 by the whole character of both groups, as may be seen from the discussions of them 

 by Stanier and van Niel (1941) and Knasyi (1944). 



Order 1. Myxobactralea [Myxobactrales] Clements Gen. Fung. 8 (1909). 



Order Myxobacteriaceae Thaxter in Bot. Gaz. 17: 389 (1892). 



Order Myxobacteriales Buchanan in Jour. Bact. 2: 163 (1917). 

 The cells not definitely of spiral form, sluggishly motile. In typical examples, the 



