Ellis. — The Life-history of Bacillus hirtus. 255 
until the requisite intensity is obtained. The exact time and amount can 
only be decided by repeated trials, and determining, by examination of 
samples under the microscope, whether the necessary intensity has been 
obtained. In my own experiments three loopfuls of Fuchsin, prepared as 
for nuclear staining, allowed to act on the material contained in 50% 
Formalin for about eight minutes, gave the best results. The cell wall is 
shown distinctly (Fig. 47) as a uniform deep-red covering to the cell (if 
Fuchsin be used), whereas the cytoplasm is much more faintly stained. 
If the proper intensity has been obtained it will be noticed that the 
cytoplasm is not uniformly stained : patches of much fainter colour appear 
(Fig. 49). These are not of equal size and are evidently the vacuoles 
characteristic of mature cells. Throughout my investigation on this form 
I have not once seen any other differentiation of the cytoplasm, so that it 
would appear as if all the substances used for metabolic or reserve purposes 
were stored in the semi-liquid condition inside these vacuoles. I was also 
not able to distinguish the nucleus. This was rather surprising, inasmuch 
as I was able to see this structure in Bac. Asterosporus , and also in the first 
stage in the development of the spore. In the latter case, however, it must 
be remembered that the nucleus is encased by a film of cytoplasm, is 
attached by strands of cytoplasm to the remainder of the protoplasm of 
the cell, and is inserted in a faintly staining area, so that it becomes a much 
more conspicuous object (Fig. 36). The internal structure thus accords 
with that of the majority of Bacteria, and is in sharp contrast to that of 
such forms as Spirillum volutans {Spir. giganteuml), in which the cell is 
always full of fat-globules and * volutans-spheres.’ The vacuoles are very 
difficult to observe, but once the proper intensity has been obtained it will 
be found that they are universally present in all mature cells. I have not 
been able to demonstrate their presence in newly germinated cells. It 
is probable that, as in newly formed vegetative cells in other plants, the 
vacuoles do not appear until the cells reach their maturity. They have 
the varieties of size and shape characteristic of vacuoles, and their presence 
accounts for the absence of other indications of the presence of reserve 
or excreted matters, for these are doubtless to be found inside the vacuoles. 
The cell wall is seen more distinctly when plasmolysis takes place, for 
the cytoplasm, owing to the withdrawal of water, contracts, leaving a clear 
space between the cytoplasm and the cell wall (Fig. 48). 
Most Constant Characteristics of Bacillus hirtus. 
The following characteristics may be accepted as the most constant. 
Spore 1 -0-1*8 ^ broad, 1 *5-2-5 /x long. Slightly oval, differentiated into 
exine and intine. Exine is bluntly pointed at both ends. 
Germination follows by means of an equatorial split. The young 
