28 MORPHOLOGY OF THE BACTERIA. 



they are formed of a myriad of little bodies iso- 

 lated or grouped, globular or linear, gifted or not 

 with motion, sometimes colored. These variations 

 constitute so many characters which require to be 

 studied with some detail. 



§ 1. Bacteria in General. 



Form. — The bacteria, as understood to-day by 

 most botanists, when considered in their separate 

 state, are of two principal forms, — globular bod- 

 ies, or monads, and bodies more or less filiform, or 

 bacteria properly so called. 



The globular bacteria comprise organisms round- 

 ed, ovoid, sometimes elongating themselves into a 

 tube (Warming). The Monas crepusculum of 

 Ehrenberg may be taken as a type. This form 

 includes also the Micrococcus of Hallier, the Mi- 

 crosporon of Klebs, the round forms of the Amy- 

 lobacter of M. Trecul, and perhaps the Microzyma 

 of M. Be"champ. We will see farther on that 

 these are very probably phases of development of 

 the spores of bacteria, properly so called. 



The bacteria, not globular, present a greater 

 diversity of form ; they may be straight, undu- 

 lating, or twisted in a spiral. 



The rectilinear bacteria are in some exactly 

 cylindrical throughout their whole extent ; and in 

 this case they form very short cylinders, as in the 

 Bacterium, Cohn, or cylinders of which the length 

 is several times as great as the thickness, as in 

 the Bacteridies {Bacillus ulna Cohn) ; others are 



