plantsfooO an& /IRotfon 143 



freely relinquished to the hotanists. These bacteria 

 are now granted to l)e the simplest plant forms, and 

 related to the algse, or sea- weeds. When one states 

 that they are so small that fifteen hundred of them 

 could stand in line upon a pin's head, and many of 

 them so diaphanous that they cannot be studied 

 under the strongest glass until their texture is re-in- 

 forced by some kind of dye-stuff, we shall conclude 

 that here we have reached the " infinitely little." 

 No wonder that for ages the very existence of bacteria 

 was unknown, and that their vast masses when made 

 evident, as by the color of some of them, were sup- 

 posed to be single individuals, as for instance the 

 myriad clusters of them which by land or water pro- 

 duced phosphorescent life. The commonest forms of 

 these minute plants are rod-shaped, spirals, spheres, 

 or egg-shaped ; of the largest, twenty-five thousand 

 in a line will occup}" an inch ; of the smallest, double 

 that number. They multiply by division. One bac- 

 terium is a single cell ; it divides, and there are two ; 

 each of these divides, and lo, four ; another division, 

 eight, and so on through infinite geometric progres- 

 sion. It is said that if let strictly alone, an unbroken 

 series from one would in five days fill all oceans with 

 a mass of bacteria a mile deep ! Fortunately the 

 series is always interrupted ; everything destroys 

 them ; yet they seem to thrive in every circumstance 



