GENERAL MORPHOLOGY AND PHYSIOLOGY 



37 



them as plants, belonging to the group fungi. It cannot be denied, how- 

 ever, that their origin (phylogeny) is still shrouded in mystery. Some sug- 

 gest that they are derived from degenerate algal forms, in common with 

 most of the fungi, while others declare that they in all probabihty origi- 

 nated as microbes. A few of the philosophical biologists, as Ernst Haeckel, 

 place them in a separate group, the Monera, which is supposed to form the 

 connecting link between plants and animals. 



Without entering into lengthy discussion, we shall, in conformity with 

 the opinion of the majority, class them as plants, belonging to the lowest 

 of the group fungi (the fungi includes rust, smuts, cup fungi, moulds, spot 

 fungi, toad-stools, etc.), namely, the Schizomycetes or fission fungi, so- 

 caUed because they multiply by fission or division. They are related to 

 the yeasts, though somewhat lower in the scale of evolution. They 

 are single-celled, each cell forming a complete Uving unit, though the 

 several units may be variously arranged into chains or clusters, or groups 

 known as zoogloea. 



The scientific grouping of microbes is as yet very unsatisfactory because 

 so little is known of their ultimate morphology, their physiology and 

 chemistry. Some have attempted to classify them as to form, others as 

 to occurrence, as to action, etc. Thus, we have: 



a. Micrococci or Coccaceae. — Globular or non-elongated microbes. 



b. Bacilli or Bacteriaceae. — Cells more or less elongated. Rod- 

 shaped microbes. 



c. Spirillae or Spirillaceae. — Cells elongated and more or less spirally 

 twisted. Or, we may have: 



a. Bacteria of earth. 



b. Bacteria of air. 



c. Bacteria of water. 

 Or, again: 



a. Chromogenic. 



b. Zymogenic. 



c. Pathogenic, etc. 



These artificial groupings could be extended indefinitely, but such sys- 

 tems of classification would be as unsatisfactory as they are unscientific. 

 The best system makes use of all of the known facts of bacteriology. 

 Several such systems have been proposed from time to time, but the new 

 discoveries along bacteriological Hnes makes it necessary to change them 

 in the course of two or three years. Migula, Fischer, Eisenberg and others 

 have proposed general systems, and a host of investigators have submitted 

 more Hmited group systems. The following classification will serve to 

 convey some idea as to the structural characteristics of the more impor- 

 tant groups : 



