THE STORY OF THE BACTERIA. I/ 



even with the most powerful microscopes, but 

 notwithstanding this, they have actually been 

 photographed, and in some cases the image 

 of the cilia, which failed to make an impres- 

 sion on the retina, has been caught and made 

 permanent by the sensitive plate in the camera. 



Warmth, moisture, oxygen, and a certain 

 amount of organic matter are the simple con- 

 ditions which are required for their activities. 



When the conditions are favorable they may 

 increase in number to a degree which is limited 

 only by their surroundings. A little constric- 

 tion appears around one of the bacteria ; it 

 grows a little longer, a partition forms across 

 the middle, and in the place of one there are 

 two full-fledged bacteria. These may at once 

 fall apart and each new individual go on di- 

 viding as before, or they may cling together, 

 forming threads or chains of varying length, 

 or clumps or masses. 



So rapid is this process of reproduction that 

 a single germ by this process of growth and 

 subdivision may give rise to more than sixteen 

 and a half millions of similar organisms within 

 twenty-four hours. It has been calculated by 



