Kingdom Mychota [17 



The metabolic systems of the Mychota are remarkably diverse. The most super- 

 ficial list of physiological types would include the following: (a) anaerobic parasites 

 and saprophytes; (b) facultatively aerobic parasites and saprophytes; (c) the vinegar 

 bacteria, being apparently the only known organisms which, while requiring organic 

 matter, are incapable of anaerobic energesis; (d) the autotrophic bacteria, the only 

 organisms which maintain life by oxidation of inorganic matter; (e) organisms living 

 by incomplete photosynthesis; and (f) organisms capable of typical photosynthesis. 



Geologically, the Mychota are ancient. Iron deposits and certain other formations 

 believed to have been produced by them occur in Archeozoic rocks estimated as more 

 than a billion years old. 



More than five thousand names have been applied to species of bacteria, but in 

 the attempt to distinguish them, only about fifteen hundred are enumerated (Ber- 

 gey's Manual, 6th ed., 1948). The species of blue-green algae are probably fewer 

 than one thousand. 



The classification of this group is inescapably highly tentative. The morphology 

 is simple and not highly varied; the physiological characters likewise appear simple, 

 but are highly varied, including many which are not known in other groups. The 

 antiquity of the Mychota makes it probable that many groups which appear to be- 

 long together consist actually of parallel developments. The undoubted antiquity of 

 the apparent main groups would lead one to place them in the category of divisions 

 or phyla; but it is not expedient to make many divisions of a group of 2500 species: 

 this would produce too many divisions of a single class or classes of a single order. 

 The kingdom is accordingly treated as a single phylum, and its main divisions as 

 classes. 



Phylum ARCHEZOA Haeckel 



yhylB. Archephyta and Archezoa Haeckel Syst. Phylog. 1:90 (1894); not Phylum 



Archephyta Haeckel (1866). 

 Phylum Myxophyceae Bessey in Univ. Nebraska Studies 7: 279 (1907). 

 Phyla Dimychota and Monomychota Enderlein Bakt.-Cyclog. 236 (1925). 

 Bacteriophyta and Cyanophyta Steinecke (1931). 

 Stamme Cyanophyta and Schizomycophyta Pascher in Beih. bot. Centralbl. 48, 



Abt. 2: 330 (1931). 

 Divisions Cyanophyta and Schizomycetae Stanier and van Niel in Jour. Bact. 42: 



464 (1941). 

 Characters of the kingdom. 



Archezoa is Haeckel's name, at the point cited, for the bacteria. The name had 

 been applied othervv^ise by Perty (1852), but not in a principal category. It will not 

 be considered inappropriate, if it be remembered that the meaning of zoe is as much 

 life as animal. 



The conventional division of the group into two classes, bacteria and blue-green 

 algae, is not perfectly natural. All of the recognized blue-green algae belong together; 

 but the recognized bacteria are a wide miscellany, some of them belonging with the 

 blue-green algae. Here three classes are recognized. 

 1. Cells without internal pigment, heterotrophic 

 or living by chemosynthesis; not usually pro- 

 ducing filaments with prominent sheaths. 



