OF FERNS FROM THEIR SPORES. 123 
their former position so as to render the existence of the enveloping cell or cells very 
evident. After the whole of the contents have been discharged, the walls of the parent- 
cell acquire a deep brown colour, presenting a peculiar appearance and making the anato- 
mical structure of the antheridium very clear (figs. 48,49). The lower faces of full-grown 
prothallia exhibit, when moderately magnified, a great number of circular bodies with 
brown roundish or squarish central patches; these are effete antheridia, with the brown 
walls of their cavities showing through the orifice at the summit (see figs. 19 & 50). 
We have next to consider the appearance of the spermatozoids, produced by the sperm- 
cells. These cells, as stated already, generally emerge entire from the antheridium, the 
spiral fibre being visible, in movement, in their interior. After a variable time, according 
to the stage of development of the spermatozoid, it breaks through the wall of the sperm- 
cell, and if perfect, escapes entirely from it. "When perfect it appears to consist of a flat- 
tened band, curled spirally into about three and a half coils, bearing all along the outer 
edge, cilia of considerable length, vibrating with great rapidity ; so much so, indeed, that 
they appear only like a fringe of light while the spermatozoid is in active motion (fig. 40). 
The filament when in the condition of the lowest specimen in the group (fig. 40) mea- 
sures about j555th of an inch in length, as coiled up; the diameter of the widest coil, 
about equal to that of the sperm-cell, is usually about 4955th of an inch. I never saw one 
uncoiled and flaccid but once; this measured about 3,3;5ths of an inch in length (fig. 42 a). 
The motion consists of a rapid rotation around its axis, which, from the spiral form, causes 
a motion of great velocity, forwards, in the water. The motion does not seem to follow 
any fixed rules; the spermatozoids dart here and there, turn aside or backwards, or alter- 
nately to the right and left in their course onward, so as to preclude the possibility of laying 
down any formula or law for it. If they come in contact by the smaller extremity with 
any fixed body, they often adhere by this point and then revolve around their axes without 
advancing. By degrees the motion becomes slackened and the rotation is lost, merely a 
kind of vibratory motion remains, and this at length ceases; but the spermatozoids seem 
to undergo dissolution during this time, and when they come to rest often appear as 
shapeless masses. By applying iodine the movement of the most active can ‚be stopped 
instantaneously, and in this way a tolerably clear view of the structure is obtained. 
Under these circumstances the cilia may be seen pretty clearly (fig. 41); the flattened 
band exhibits minute granules adhering to it, and is seen to have a little rounded head, 
from which the coils run back, increasing successively in diameter, so as to give a conical 
form to the outline of the whole, as seen at the side. 
Such, so far as I can make it out, is the character of a perfect spermatozoid. But these 
bodies acquire the capability of motion, of whatever nature this may be, before they are 
: : i t ts which different observers 
perfectly developed, and hence, I imagine, the different accoun 
have given of them. It seemed to me that when they had not acquired their full develop- 
ment, the fibres could not unroll into the true form when they emerged from the eperm- 
cell; they thus appeared to present fewer coils, often ‘only one and a half, the latter of 
very large diameter; in other cases they looked like minute shells of Gasteropodous Mol- 
lusks. In fig. 46 I have given representations of several of these forms, and it should be 
observed that these imperfect forms exhibited a greater quantity of adherent granules, and 
