140 SCHIZOMYCETES 



minutes but practically all are killed if the boiling is 

 continued for ten minutes. 



Germination. When transplanted to suitable media 

 and placed under favourable conditions, the spores 

 germinate, usually within twenty-four to thirty-six 

 hours, and successively undergo the following changes 

 which may be followed in hanging-drop cultures on a 

 warm stage: 



1. Swell up slowly and enlarge, through the absorp- 

 tion of water. 



2. Lose their refrangibility. 



3. At this stage one of three processes (but the par- 

 ticular process is always constant for the same species) 

 may be observed: 



(a) The spore grows out into the new bacillus 

 without discarding the spore membrane (which in 

 this case now becomes the cell membrane) ; e. g., B. 

 leptosporus. 



(b) It loses its spore membrane by solution; e. g., B. 

 anthracis. 



(c) It loses its spore membrane by rupture. 



In this process the rupture may be either polar (at 

 one pole only e. g., B. butyricus), or bipolar (e. g., 

 B. sessile), or equatorial; (e. g., B. subtilis). 



In those cases where the spore membrane is discarded 

 the cell membrane of the new bacillus may either be 

 formed from 



(a) The inner layer of the spore membrane, which 

 has undergone a preliminary splitting into parietal 

 and visceral layers; e. g., B. butyricus. 



(b) The outer layers of the cell protoplasm, which 

 become differentiated for that purpose; e. g., B. mega- 

 therium. 



The new bacillus now increases in size, elongates, 

 and takes on a vegetative growth i. e., undergoes 

 fission the bacilli resulting from which may in their 

 turn give rise to spores. 



