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this veil; and when it is withdrawn, a portion re- 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; and 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 In some unpublished experi- 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.” 
“Tt 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 
