ARCHER, ON SPIROTANIA. 189 
Shortly the cell-contents of each opposite parent-cell so 
lying side by side become separated into two portions, which 
by degrees become more and more contracted into a shorter 
and shorter elliptic mass. As the contraction of each half of 
the contents of each cell advances, the spiral arrangement 
becomes more and more obliterated, until finally there is little 
or no trace left of the original spiral band. (Pl. VIIL, fig. 5.) 
It is to be regretted that the observation is here insofar in- 
complete that | can give no record of what becomes of the 
nucleus during this process. Even though it became divided 
along with the separation of the cell-contents into two por- 
tions, and were there actually a new nucleus in each half, it 
could not be indeed now seen, as the green contents become 
so much more densely packed than when, as a spiral band, 
they occupied the whole cavity of the parent-cell. 
The outer wall of the parent-cell, now enclosing the two 
elliptic masses of contents, is still to be seen (fig. 5); it is 
thin, and hardly presents a double contour. By degrees it 
seems to get more and more faint, vanishing finally, probably 
by solution. 
Now begins the conjugation. Each elliptic mass derived 
from one of the parent-cells passes over and becomes conju- 
gated by complete fusion with the corresponding opposite 
portions derived from the other parent-cell (fig. 6). That is, al- 
though the two portions of each original parent-cell may now 
be regarded as physiologically distinct sister-cells, being in fact 
daughter-cells without a special wall, they do not conjugate 
with each other, but with the respective halves or daughter- 
cells opposite to them. In other words, regarding the original 
parent-cells as placed side by side vertically, the upper half 
of the contents of the left-hand cell becomes conjugated with 
the upper half of the contents of the right-hand cell, whilst 
simultaneously therewith the lower half of the contents of 
the left-hand cell becomes conjugated with the lower half of 
the contents of the right-hand cell. Consequently, in every 
case of conjugation in this plant there are two zygospores 
formed, the four masses having become mutually amalga- 
mated into two. 
At an early stage each zygospore becomes surrounded by 
a halo of mucus, which by degrees seems to become more 
and more dense and more definitely bounded. Each nascent 
zygospore, at first of a more or less irregular figure-of-eight 
shape, finally wholly coalesces to a spherical form; and each 
then acquires a definite, smoothly bounded cell-wall, the 
contents being densely granular (fig. 7). 
Now, if observation ceased here. we should have but an 
