FORM AND STRUCTURE OF MICROBES 59 



The spores which develop in the interior of bacteria are 

 endospores. The name of arthrospores has been given to those 

 rounded granules which certain bacteria produce by segmenta- 

 tion, by a sort of pinching off, or perhaps by a shrinking of 

 their substance ; for example the cholera vibrio, which does not 

 possess endospores. 



The properties of an anthrax bacillus are fixed, and 

 transmitted to the new generation, by a sort of heredity, by 

 means of the spore. 



It is not impossible that some sexual differentiation exists in 

 the sporulating bacteria. 



Pleomorphism of Bacteria. The bacterial forms have 

 not the immutability of crystals, nor even the relative stability 

 of species among the higher plants and animals. They are 

 variable to an extent that absolutely confounds the bacteriolo- 

 gist. In a pure culture such a diversity of forms may appear, 

 forms long and short, rounded and thread-like, that the culture 



FIG. 28. Involution forms : I. Lactic bacilli. 2. Bacillus subtilis. 

 3 Anthrax bacilli. 



might be thought impure. The bacillus of diphtheria trans- 

 ferred from a natural to an artificial medium, or from one 

 artificial medium to another, appears short or long according 

 to circumstances and gives in old cultures forms which 

 resemble staphylococci. One bacterium exists so variable 

 that it has been called Proteus, the protean bacillus. The 

 Bacillus prodigiosuS) the bacterium which gives red colonies 



