468 Ferguson — The Development of the Egg and 
occurring in the upper, outer portion of the achromatic spindle 
during the division of the central cell. There are probably 
instances in which no membrane is developed about this 
nucleus ; in such cases the chromosomes never fuse to form 
a network. The ventral canal-cell rarely presents the appear- 
ance of a normal cell ; at the time of fertilization it usually 
persists as a small, somewhat crescent-shaped, deeply stain- 
ing body, which lies just beneath the neck-cells of the 
archegonium and above, but in contact with, the cytoplasm 
of the egg. 
During the maturation of the egg, many nutritive spheres 
arise in its cytoplasm. At first these are irregularly scattered 
throughout the cell, though more prominent at its periphery ; 
in the mature egg, they are largely confined to the peripheral 
portions of the lower half of the cytoplasm. It is suggested, 
though not definitely demonstrated, that these nutritive spheres 
are the products of nucleolar activity, having originated within 
the nucleolus of the egg and the nucleoli of the sheath-cells. 
As the egg-nucleus assumes its central position in the 
oosphere, it increases much in size, and many fibres arise in 
the cytoplasm surrounding it. These threads have, in general, 
a radial arrangement and are most prominent along the upper 
side of the nucleus. The structure presented by the growing, 
and also by the mature, egg-nucleus may vary from a most 
delicate network bearing minute granules, to an interrupted, 
imperfect reticulum composed of large, irregular, diffusely- 
staining elements. These various aspects are doubtless the 
expressions of the different physiological activities with which 
this nucleus is concerned. The normal egg-nucleus has one 
large, vacuolate nucleolus and a variable number of small, 
secondary nucleoli. There is no evidence of the presence in 
this nucleus of a special metaplasmic substance. 
The egg-cytoplasm presents a delicate reticulum, in which, 
at times, many fibres occur. Immediately preceding fertili- 
zation, an opening arises in this cytoplasm, just below, or in 
the near vicinity of, the neck-cells. This cavity is apparently 
formed for the reception of the sperm-cell. 
