140 PHYSIOLOGY OF THE BACTERIA. 



that there are three thousand cells in a square mil- 

 limetre, which is below the truth, this will give 

 for the vat three hundred milliards of cells pro- 

 duced in a very short time." 



" The Mycodermi aceti is not always the same. 

 Usually it forms upon the surface of a liquid a 

 soft-looking veil, smooth at first, then wrinkled, 

 which is with difficulty submerged and moistened. 

 If a glass rod is plunged into the liquid, it pierces 

 this veil ; and when it is withdrawn, a portion re- 

 mains attached to the rod ; aaid the opening made 

 immediately disappears, being occupied by the veil 

 which seems never to have room enough in which 

 to extend itself. In some unpublished experi- 

 ments I have frequently observed another form of 

 veil, dryer, finer, and sometimes showing prismatic 

 colors. This veil does not wrinkle, but is covered 

 with crossed undulations, having sharp edges, 

 which recall the surface of a honeycomb. Sowed 

 upon the surface of various liquids, it reproduces 

 itself identically, and it is difficult not to consider 

 it a different form of the preceding. Finally, I 

 have also met a species of mycoderma producing 

 well-developed veils, but having scarcely any acet- 

 ifying power, and reproducing itself with this 

 character." 



"It is difficult to distinguish these forms the one 

 from the other, by the microscope, because of their 

 minuteness. We may, however, say that the second 

 which I have described is sensibly smaller than 

 the first, and the third more attenuated than either 

 of the others. However, the differences are feeble." 



This veil is called the mother of vinegar. The 



