276 Shaw. — The Fertilization of Onoclea . 
the egg from injury or from multiple fertilization by them. 
A few careful experiments in fixing archegonia before and 
after the first spermatozoid enters the egg ought to reveal 
the truth of the matter. 
Within half an hour after the entrance of the sperma- 
tozoids into the archegonium the canal is practically closed 
by the expansion of the four proximal neck-cells and the four 
just beyond them. The egg gradually recovers its turgidity 
and forces the free spermatozoids against the outer wall of 
the venter (Fig. 3). The membrane which, from analogy 
with the development of the eggs in other plants, we would 
expect to form around the egg immediately after the entrance 
of the spermatozoids, was not seen in any of the earlier 
stages. If the membrane is of the nature of cellulose it 
ought to be brought out distinctly by the Bismark-brown 
with which the subject of Fig. 1 was stained on the slide. 
This stain colours even the cytoplasm in this case. In all 
the preparations which were examined there was no evidence 
that a membrane of appreciable thickness is formed im- 
mediately after the entrance of the spermatozoid or for 
some time afterward. A conclusion so contrary to analogy 
must remain in doubt. It may be that the chromic acid 
used for too long a time destroyed the membrane. 
The early history of the spermatozoid inside the egg was 
not satisfactorily followed. After the ten- and twenty-minute 
periods the collapsed state of the egg interfered with the 
study of the enclosed spermatozoid, and the stains used for 
these stages were not the best. The difficulty was increased 
by the free spermatozoids crowding into the concavity of 
the egg. So the mode of entrance of the spermatozoid into 
the egg cannot now be described. In one case the sperma- 
tozoid appeared to be still outside the egg-nucleus, against 
which it lay in an open coil after an hour, but in other cases 
it was found inside the egg-nucleus within thirty minutes. 
The nucleus of the spermatozoid undergoes no visible change 
in structure while in the egg-cytoplasm. Whether the 
cytoplasmic wing and the cilia of the spermatozoid are taken 
