86 Fermentation and Kindred Phenomena. 



life history, and the methods which have been invented for their 

 study. The organisms in question are very numerous, and di- 

 verse in size and form. Naturalists have found much difficulty 

 in assigning them to their proper kingdom ; and, in fact, from 

 time to time have transferred them from one kingdom to 

 another ; at one period considering them to be animals, at 

 another vegetables. At any rate they are among the lowest 

 types of life, and may be considered to be on the borderland 

 between plants and animals ; but at last they have been 

 definitely claimed by the botanists. 



They have as a class been called by different names. Haeckel 

 termed them " Protista," Sedillot "microbes," and they include 

 besides the different varieties of yeasts, moulds, and fungi, the 

 so called "splitting fungi" (spalt pilze) or " schizomycetes," in 

 allusion to their peculiar mode of reproduction. These latter 

 are of especial importance, and I shall in the rest of this lecture 

 deal with them exclusively. 



The classification of the schizomycetes has not yet been 

 definitely settled. It will be sufficient for our purpose to describe 

 the appearance of some of the chief varieties. 



Micrococci. — Minute round organisms, sometimes arranged 

 in groups of two (dumb-bells, dysfisococci), or of four (tetrad), 

 or in packets of tetrads (sarcinci). Very frequently they are 

 found in chains (streptococci). 



Bacteria and Bacilli. — The first short, the second longer 

 rods, often arranged in groups of two, or in chains of many. 

 They are frequently motile, darting about with great rapidity. 

 The movement is caused by a whip-like appendage (flagellum) 

 attached to one end of the organism. 



Leptothrix. — Long filaments, often branching out in different 

 directions. 



Spirillum. — Organisms which are twisted, often like a cork- 

 screw, and which move with great rapidity. 



Modes of Reproduction. — The schizomycetes, as I have before 

 mentioned, are so called on account of their peculiar method 

 of reproduction, i.e., by splitting in one or more directions, 

 each fragment becoming a mature organism and again sub- 



