6 
POPULAR SCIENCE REVIEW. 
filament becomes much longer. This is the ordinary mode by 
which the growth of filaments in the confervoids is effected. 
There is one more point of interest in the cell of this plant. In 
the centre (fig. 9) you may perceive, by a little trouble in 
44 focusing,” a transparent colourless body, giving off arms to 
all parts of the cell, so that it is suspended in the centre. This 
is the nucleus, and allusion has been made to this body above. 
Through the centre of this nucleus passes the line of division 
above described. 
But the phenomenon which has attracted so much attention 
from observers is that which has been called 44 conjugation,” 
and thence the class of plants in which this takes place (for 
there are many) have been called the Conjugated. As the term 
implies, the process is a joining together of two cells. Ordi- 
narily, it takes place between two cells of two neighbouring 
filaments ; a projection is sent out by each, which meet and 
unite. During this time, the green spiral band of each cell losing 
its character, the coils melt together, and then those of one 
side pass over through the tube of junction into the other cell, 
mingling with the other green mass ; and they then are intimately 
blended into one large oval green mass, the spore (fig. 10, a, 6). 
Soon after this the spore becomes hardened on the exterior, a 
cell-wall is formed round it, and it is subsequently liberated 
upon the dissolution of the parent cell ; in the course of the next 
spring it elongates, the contents assume the form of the spiral 
band, and a cell is thus formed like those of last year ; in due 
time, it divides as before mentioned, and thus a filament of 
Spirogyra is reproduced. In some of the species of this genus, 
if there is no filament near enough with which to conjugate, the 
adjoining cells of the same filament conjugate, for a process is 
throughout from each cell round the joint, and then their con- 
tents fuse as above described. 
Now what is the exact meaning of this curious occurrence ? 
Opinions vary somewhat. Some see in it the analogue of the 
fertilisation affected by means of the pollen, and, as above 
shown, in the Vaucheria, only not carried to so complete an 
extent. Others look upon it as a mere vegetative action, because 
the contents of the cells involved have no visible difference 
before nor during conjugation, and that it is rather to sustain 
the vigour of growth in the plant, which it may lose by repeated 
division. However this may be, it is at present our safer plan 
to continue to watch the process, and also to observe whether, 
in the same plant, any real antherozoids can be found at any 
time of its life. A careful observation of this plant would be 
highly interesting to the observer, and doubtless add valuable 
facts to set at rest this question. 
Other changes have been observed in this plant. For instance, 
