mass of about thirty-two sperm
cells is formed, each giving rise to a large spirally-coiled
spermatozoid. When ripe, the mass of sperm cells crowds so upon the
outer cells as to render them almost invisible, and as they ripen
they separate by a partial dissolving of the division walls. When
brought into water, the outer cells of the antheridium swell
strongly, and the matter derived from the dissolved walls of the
sperm cells also absorbs water, so that finally the pressure becomes
so great that the wall of the antheridium breaks, and the sperm
cells are forced out by the swelling up of the wall cells (_N_,
_O_). After lying a few moments in the water, the wall of each sperm
cell becomes completely dissolved, and the spermatozoids are
released, and swim rapidly away with a twisting movement. They may
be killed with a little iodine, when each is seen to be a somewhat
flattened band, coiled several times. At the forward end, the coils
are smaller, and there are numerous very long and delicate cilia. At
the hinder end may generally be seen a delicate sac (_P_, _v_),
containing a few small granules, some of which usually show the
reaction of starch, turning blue when iodine is applied.

In studying the development of the antheridia, it is only necessary
to mount the plants in water and examine them directly; but the
study of the archegonia requires careful longitudinal sections of
the prothallium. To make these, the prothallium should be placed
between small pieces of pith, and the razor must be very sharp. It
may be necessary to use a little potash to make the sections
transparent enough to see the structure, but this must be used
cautiously on account of the great delicacy of the tissues.

If a plant with ripe archegonia is placed in a drop of water, with
the lower surface uppermost, and at the same time male plants are
put with it, and the whole covered with a cover glass, the
archegonia and antheridia will open simultaneously; and, if examined
with the microscope, we shall see the spermatozoids collect about
the open archegonia, to which they are attracted by the substance
forced out when it opens. With a little patience, one or more may be
seen to enter the open neck through which it forces itself, by a
slow twisting movement, down to the egg cell. In order to make the
experiment successful, the plants should be allowed to become a
little dry,