32 TAXONOMY 



of shape in the rod. The names of the genera might be formed con- 

 veniently in such a way that the root of the word indicated the shape of the 

 cell, and the termination the arrangement of the cilia. The root-words 

 might be baktron (rod), kloster (spindle), and plectron (drum-stick), and the 

 terminations -inium for monotrichous, -ilium for lophotrichous, and -idium 

 for peritrichous types. The classification of the less numerous spirilla is, 

 as the table shows, a simpler matter. Among the Coccaceae the manner 

 of cell-division has already been employed as a generic character, but 

 greater weight should be attached to the contrast between two more 

 comprehensive groups into which they naturally fall. These are the 

 Homoccocaceae, where the planes of fission follow a definite sequence, and 

 the Allococcaceae, in which such regularity is not found (see pp. 18 and 19). 



The different meanings attached to the words Bacillus and Bacterium 

 deserve notice. In two of the most recent systems of classification (21) the 

 senses in which they are used have little in common. Lehmann and 

 Neumann apply the word Bacterium to all rod-shaped forms in which spores 

 are unknown (a point in regard to which any day may bring a change in 

 our knowledge), the genus Bacillus embracing those in which spores have 

 been found. Of the manner of ciliation no notice is taken. Migula, on 

 the other hand, uses the term Bacterium for all non-motile rods, and Bacillus 

 for peritrichous species, the remaining motile forms, both lophotrichous and 

 monotrichous, constituting a new genus, Pseudomonas. This classification 

 very properly regards the presence or absence of spores as unimportant ; 

 but the shape of the spore-bearing rod is neglected, and no distinction is 

 made between monotrichous and lophotrichous species. Perhaps the best 

 plan would be to drop altogether the word Bacterium as a generic term, 

 seeing that it is now used as a collective name for the whole group of micro- 

 organisms. The word Bacillus might then be used, in memory of Koch's 

 first work, for all those species which, like the anthrax parasite, are non- 

 motile and retain their shape during sporulation. 



At present we are not justified in regarding the presence or absence of 

 capsules as sufficiently important to constitute a generic character, although 

 very useful for the differentiation of species. 



The trichobacteria are so few in number that it will suffice at present 

 to unite them in a single family representative of another order. 



Based on the characters that have been under consideration, a classifi- 

 cation of the bacteria might be arranged as follows : — 



Order 1. HAPLOBACTERINAE. 



Vegetative phase unicellular, spherical, cylindrical, or spirally twisted; isolated or. 

 united in chains or clusters. 



Family I. COCCACEAE. 

 Vegetative cell spherical. 



