ON THE MODE OF GROWTH OF SOME OF THE ALGJ2. 
7 
the spiral contents coalesce so as to form a number of globular 
portions, each leaving tivo cilia at one end, possessing power of 
movement in the parent cell. When this latter breaks up, these 
bodies move about freely, and appear like the zoospores of 
other algge (fig. 11). Again, instead of the contents resolving 
themselves into the above form, they become converted into a 
star-like form, with firm cell-walls. These again, according to 
Pringsheim, bcome converted into active moving bodies, whose 
history has yet to be followed. 
Some plants conjugate which only consist of one cell (fig. 12 , a). 
The contents of one cell wholly pass over into the other, or re- 
main in the tube of junction, distending it by its growth (fig. 
12, 6). A good example is seen in Cylindrocystis Brebissonii 
(fig. 12). 
Now let us watch another of these lower forms which present, 
as far as at present investigated, a simpler, but more rapid, 
form than the above in its mode of increase. You may find, 
in autumn and early spring, at the foot of trees, walls, and 
palings, green wavy filaments, which readily mat together when 
taken up (figs. 13-17). 
This plant has been called Prasiola. Its early condition as a 
single filament was called Lyngbya (fig. 13), and the next 
stage Schizogonium (fig. 14), till the writer pointed out the 
unity of all these in the Microscopical Journal of 1861. 
The first stage consists of a green filament divided into many 
cells, the walls of which are rather thick. The green contents 
are sometimes uniform, sometimes granular (fig. 13). By con- 
stant division of these cells across the filaments, the length of 
the filament increases. But after a time another form of divi- 
sion arises, each cell dividing at right angles to the former line, 
so as to become quartered, and to make four new cells (fig. 14), 
and thus the fibre becomes by the growth of each wider, with 
the appearance of a colourless line down its centre (fig. 14). 
After a time, each of these divisions divides again in the qua- 
ternary fashion, and a broad strap is produced, which was called 
Schizogonium. By the still further extension of this process, 
large flat wavy bands are produced, generally wider at one end, 
retaining, however, in the arrangement of the green cell con- 
tents, evidence of its mode of origin. This latter form has 
been called Prasiola. But after a time this strap-shaped frond 
reverts to the filamentous forms (fig. 15), by the converse of 
the plan above named. The quaternary division ceases, the 
simple filamentous is substituted, and these separate from one 
another, ultimately becoming free; and thus the number of 
the species is increased. But this is also accomplished upon 
another plan. One of the cells of the filament sometimes grows 
three times its original size, and then, separating from the rest 
