of Bacteria and their Allies by Heterogenesis. 389 
on the forms of Bacteria and begin to exhibit swarming 
movements. This may be commonly seen in cases where the 
cell-wall presents a perfectly healthy appearance and where 
there is absolutely no indication of infection taking place 
from without. 
The same kind of thing is often to be observed within the 
thick-walled resting-spores both of Vaucheria and Spirogyra. 
There is the appearance of motionless particles in some part 
of the spore, the appearance of Bacteria in the midst of these 
particles, and the gradual assumption by the Bacteria of 
swarming movements. Observations of this kind were not 
unfrequently made in cases where these resting-spores had 
been undergoing one or other of the changes that I have 
previously described. 
Again, I have occasionally seen a development of motion- 
less Micrococci and Bacilli taking place inside the thick wall 
of a Mitella cell, between it and the chlorophyll layer, such as 
is shown in Pl. XXV. fig. 1 (x 700). Yet the normal 
cyclosis was still going on within this cell, showing that 
there could be no apertures or solutions of continuity of any 
kind; and all the microorganisms to be seen in different 
stages of development in this layer were quite motionless, so 
far as could be observed. Their imperfect definition in the 
photograph, however, makes it possible that absence of spon- 
taneous movement was not absolute, unless the slight blurring 
may have been due to vibrations during the prolonged expo- 
sure needful to enable the light to pass through the whole 
thickness of the filament. Their appearance along a parti- 
cular band of the filament only is, of course, due to the parts 
on either side being out of focus. 
I have also endeavoured to throw light upon this question 
in another way, that is, by repeating, with variations, some 
of the experiments of Lechartier and Bellamy, by which they 
studied the fermentation that occurs in various vegetables and 
fruits when shut up within hermetically sealed vessels. They 
showed that the oxygen of the air was soon consumed by the 
vegetables or fruits, which then began to break up sugar, to 
give off carbonic acid, and to produce alcohol and acetic acid. 
They came to the conclusion in 1872 * that this fermen- 
tation might certainly occur without the production of the 
alcoholic ferment. ‘They, in fact, adopted Pasteur’s view 
that the formation of alcohol in these cases was due to the 
altered activity of the cells of the fruit, which, in the absence 
of free oxygen, act after the fashion of ferments. In a later 
* Compt. Rend. 1872, ii. p. 1203. 
Ann. & Mag. N. Hist. Ser. 7. Vol, xii. 96 
