232 Rickett.—Fertilization in Sphaerocarpos . 
shrinkage due to fixation, for in living archegonia freshly dissected out the 
egg may be observed through the wall of the venter as a darker body lying 
free in the cavity. The action of the fixing fluid is shown, however, by the 
slight irregularities in shape of several of the eggs figured. The cytoplasm 
of the egg is dense, of a fine structure, and stains very deeply. The nucleus 
lies in the centre of the egg, and is also of an ovoid form, measuring about 
13 by 10 /x. In the telophases of the last division of the central cell, which 
gives rise to the egg and the ventral canal cell, the nucleus contains a small 
mass of very deeply staining chromosomes, so tightly packed together that 
nothing can be made out of their structure or number. In the resting 
nucleus of the egg the chromatin is still in a close mass in the centre, about 
the nucleolus, surrounded by a clear space which in turn is bounded by the 
nuclear membrane. Certain strands and granules are to be found in this 
clear area. Occasionally a nucleus is found having a more open structure, 
and in such cases the chromatin is seen to be still largely in the form of rods 
and threads. One nucleus of the latter type is shown in PI. Ill, Fig. 2 . 
In the centre is a large nucleolus. 
There is no indication of any receptive spot in the cytoplasm of the 
egg. This corresponds with Kruch’s (1891) account for Riella. A recep¬ 
tive spot has been described by Strasburger (1870) for the egg of Mar- 
chantia , by Humphrey (1906) for that of Fossombronia , and by Campbell 
(1888, 1918) for the eggs of Targionia , Funaria , Pilalaria , and several 
ferns. In all these forms it is described as a more hyaline area of the cyto¬ 
plasm near the apex of the egg. In Sphaerocarpos there are many cases 
(see especially Figs. 4 and 9 ) in which the distal end of the egg (the upper 
end in the figures) is flattened or even slightly concave. Garber (1904) 
described a similar concavity at the distal end of the egg of Riccia natans. 
It is possible that what is known as the ‘ receptive spot ’ appears only under 
the influence of certain technical methods. The flattened or concave portion 
of the egg in my preparations may be indicative of a local structural 
difference, which under a different fixation might appear as a hyaline area. 
There are conflicting statements as to the presence of a receptive spot in the 
eggs even of the same form, for Durand (1908) denies the existence of such 
a spot in Marcliantia. 
At maturity the four canal cells that fill the neck, together with the 
ventral canal cell, break down, and the mucilaginous material derived there¬ 
from streams out from the mouth of the archegonium. This material may 
be seen in preparations as a densely stained, coagulated, somewhat stringy 
mass, filling the neck canal and part of the venter, and extending out 
from the neck. The egg is now ready for fertilization, and apparently 
remains so for only a short time. If not fertilized, the egg disintegrates, 
this change being evidenced first by a great increase in its (already marked) 
staining capacity, by a massing together of the nuclear materials, and 
