468 THIRD PART.—BACTERIA OR SCHIZOMYCETES. 
refringent, splits across the middle in germination after its first distension into two 
portions, which however remain firmly united at one side. The protoplasm invested 
with a delicate membrane elongates in the direction of the longer axis of the spore 
and of the longer axis of the mother-cell which coincides with it, and at the same time 
usually bends through about 90°, and one extremity is thus thrust out of the opening in 
the outer wall of the spore while the other extremity remains in the spore. The 
“protoplasmic body then developes into a rod. It appears from these phenomena as if 
the direction of longitudinal growth in this case in germination is at right angles to 
that of the parent-filament, but this is not really so. The wall of the spore which has 
opened on one side is evidently very elastic; it manifests so considerable a resistance 
to the elongating rod as it bends, that the rod with both its extremities fixed in the 
spore becomes curved before the one extremity is set free. The resistance sometimes 
goes so far that both extremities remain in the spore, and in that case the elongating 
rod assumes the form of a horse-shoe, the limbs of which may be of considerable 
length. In other respects its growth is entirely the same as the ordinary growth which 
begins with the formation of a bend in the protoplasm, and if the rod subsequently 
divides into partial rods, two separate rods answering to the two limbs of the horse- 
shoe may often be seen to project side by side from the ruptured wall of the spore 
(Fig. 105 B, 4, 8). 
The cells produced in germination grow and divide by the formation of transverse 
walls ; the products of this growth do not however remain united in a filament, but 
separate one after another into rods consisting of a few or in many cases of a single 
cylindrical cell, which may be 4-5 times longer than broad. These rods, which multi- 
ply very rapidly and abundantly in fluids containing a good supply of food, display 
active swarming movements all the time of the kind described above. I was unable to 
satisfy myself with regard to the presence of cilia or flagella during the swarming stage 
even in Bacillus subtilis. ‘The rods become disseminated through the fluid as they 
swarm and render it turbid. The last stage of vegetation is indicated by the entrance 
into a state of rest, in which the cells increasing greatly in size remain united 
together in filaments and the filaments form pellicles, till at last formation of spores 
begins afresh. 
6. ARTHROSPOROUS BACTERIA. 
Section CXXXI In the course of the development of the species in this group 
single members may simply separate from their connection with others, and under 
suitable conditions become the initial members of new combinations; they may there- 
fore claim to be called spores. In other respects there is no general characteristic 
distinction between them and the purely vegetative members. 
In connection with the fact ‘that the species in this group are less like one another 
than the Endosporous Bacteria, and that some species have a greater variety of 
growth-forms, the mode of formation of the cells which may be termed spores varies 
greatly in the different species. 
It is to the forms of this group that I give the name Arthrobacterium proposed 
for them in my introduction on page 454; they resemble Bacillus in their vegetative 
form, and are usually known as species of Bacterium, but require a more exact. 
