points, and is there pierced with rounded holes. At the
same time the plasma is divided into a larger or smaller number of
distinct portions, which are rounded into little spheres, and separate
from the walls of the conceptacle in order to group themselves at the
centre, where they float in a watery fluid. These gonospheres are then
smooth and bare, with no membrane on their surface of the nature of
cellulose.

[Illustration: FIG. 97.--Conjugation in _Achlya racemosa_. (Cornu.)]

During the formation of the oogonia there arise from its pedicel
or from neighbouring filaments slight cylindrical curved branches,
sometimes turned round the support of the oogonia, and which all tend
towards this organ. Their superior extremity is intimately applied
to its wall, then ceases to be elongated, becomes slightly inflated,
and is limited below by a partition; it is then an oblong cell,
slightly curved, filled with protoplasm, and intimately applied to
the oogonia--in fact, an antheridium or organ of the male sex.
Each oogonium possesses one or several antheridia. Towards the time
when the gonospheres are formed it may be observed that each
antheridium sends to the interior of the oogonia one or several
tubular processes, which have crossed its side wall, and which open
at their extremity in order to discharge their contents. These,
while they are flowing out, present some very agile corpuscles, and
which, considering their resemblance to those in _Vaucheria_, to
which the name of spermatozoids are applied, ought to be considered
as the fecundating corpuscles. After the evacuation of the antheridia
the gonospheres are found to be covered with cellulose; they then
constitute so many oospores, with solid walls. De Bary considers
that, bearing in mind analogous phenomena observed in _Vaucheria_, and
the direct observations of Pringsheim,[G] the cellulose membrane on
the surface of the gonospheres is only the consequence of a sexual
fecundation.

In _Achlya dioica_ the antheridium is cylindrical, the plasma which it
encloses is divided into particles, which attain nearly the size of
the zoospores of the same plant. These particles become globose
cells, grouped in the centre of the antheridium. Afterwards the
contents of these latter cells become divided into numerous bacillary
spermatozoids, which first break the wall of their mother cell, and
then issue from the antheridium. These rod-like corpuscles, which
resemble the spermatozo