592 MurrilL—Fite Development of the Archegonium 
suggests a sperm-nucleus with its membrane breaking away, 
and the contents dissolving in the nuclear substance of 
the egg. 
The large vacuole at the centre of the egg changes its 
position as the nucleus moves down, and, passing it on one 
side (Fig. 34), comes to lie near the apex of the cell. The 
vacuole is apparently somewhat diminished in size as the 
egg-nucleus increases, and it is not improbable that some 
of the cell-sap from the vacuole passes into the nucleus while 
they lie near together. The concentration of cytoplasm and 
food materials near the centre, in consequence of the change 
in position of the nucleus, leaves more room for the vacuole 
near the apical portion of the egg. Another vacuole with 
contents very similar to those of the nucleus is regularly 
observed 1 in the mature egg situated just beneath the ventral 
canal-cell (Fig. 10). It is quite different from the proteid- 
vacuoles in appearance, but seems to originate in one or more 
of the latter upon the relief of pressure in the apical region 
by the enlargement of their enclosing membranes and the 
expansion and distribution of their contents. This ‘ nuclear 5 
vacuole sometimes fuses with the ‘ empty 5 vacuole as it 
approaches the apex, but the latter more often remains to one 
side and a little below the former. Near these two vacuoles 
is the receptive spot of the egg. 
The ventral canal-cell is fairly persistent in Tsuga. When 
division is completed its nucleus is equal in size and similar 
in structure to the nucleus of the egg, and for some time 
shows the same stages of development. But when the nucleus 
has nearly filled the ventral canal-cell its membrane becomes 
wavy in outline, the scanty reticulum occupies only a small 
portion of the nuclear cavity, and the nucleoli remain minute 
and scattered. Growth having ceased, signs of disorganization 
soon appear. The nuclear contents become amorphous and 
stain diffusely, while the nucleus and the cell become more 
1 An archegonium rendered very abnormal by developing far down on the side 
of the prothallium showed this nuclear vacuole in all respects normal. 
