VI] GENERAL CHARACTERS OF BACTERIA 113 



in the form of a pale rod thinner than the spore itself; as it 

 elongates it protrudes more and more from the rest of the 

 spore, its free end being rounded, while at the same time 

 the rest of the spore outline becomes thinner and less dark ; 

 ultimately the whole spore has been consumed as it were in 

 the formation of the rod, which now looks like a cylindrical 

 bacillus of the same character and aspect as the bacilli from 

 which originally the spore had been derived. The bacillus 

 once formed divides and then continues to grow and 

 multiply. The time required for the production of a 

 bacillus from a spore varies with the different species. 

 Koch observed the germination of the spore into a baciDus 

 anthracis to be completed in about an hour ; the writer has 

 observed the time required for the complete formation of a 

 bacillus from a spore of the bacillus filamentosus in broth, 

 in the " suspended drop," at 37" C. to be certainly less than 

 one hour ; that of bacillus anthracis between one hour and 

 a half and two hours ; that of the bacillus subtilis of hay 

 infusion to be more than one half but less than one hour. 

 Occasionally one meets in these observations with motile 

 bacilli to which a spore which has not yet commenced to 

 germinate is attached and is dragged about by the former : 

 this evidently indicates that of two spores originally joined 

 by interstitial material {see spores in threads) only one has 

 already changed into a motile bacillus — the other has not 

 yet so changed. 



Motility} — One of the most interesting phenomena shown 

 by bacteria is the power of active locomotion possessed by 

 some species. When examined under the microscope in a fluid 

 medium all bacteria show the kind of oscillation known as 

 Brownian molecular movement; but in some species there is 



1 Copied from Klein's article in Stevenson and Murphy, vol. ii., 

 p. 13 and fassim. 



I 



