Rickett.—Fertilization of Sphaerocarpos . 
253 
Table III. 
Cases showing Cytoplasmic Granules . 
Time after flooding. 
Phase. 
Series. 
Hrs. 
Min. 
J.VU. UJ 
cases. 
5 
C 
40 
2 
4 
A 
48 
7 . 
7 
D 
6 5 
30 
2 
8 
D 
6 5 
30 
1 
5 
C 
66 
1 
6 
D 
7 l 
30 
1 
7 
D 
75 
45 
4 
18 
It may be that these bodies represent an excess of food material in the 
cytoplasm. On the other hand, their appearance may be due to slight 
differences in the action of the fixing fluid, which in turn are perhaps due to 
slight differences in the condition of the cytoplasm. The substance that is 
usually present instead of the granules seems to be, as already mentioned, 
a dense, homogeneous, presumably colloidal material; and the appearance 
of a system of granules may be caused by a coalescence of one of the 
phases of the colloid, leading to the production of large droplets. 
Both the rows of granules, and, in some cases, the radiating processes 
extending out from the polar caps, present under the low power of the 
microscope an appearance similar to that of two asters. It is interesting in 
this connexion to recall that centrosomes have been described in several 
Liverworts, notably in Pellia and Marchantia , in various tissues of both 
sporophyte and gametophyte. Centrosomes, with distinct radiating fibres, 
have been described in the fertilized egg of Preissia quadrata by 
Miss Graham ( 1918 ), and in that of Riccardiapinguis by Florin ( 1918 ). In 
the former case the radiations which form the aster are definite, easily 
visible fibres, and in the centre is a small definite body. In the latter they 
are apparently close rows of fine granules, which merge together in small 
dense masses (‘ centrosome-like bodies') near the poles of the nucleus. 
In Sphaerocarpos such rays as are present, though fibrillar in nature in 
some stages, are much less regular than those described by these workers, 
and converge upon no definite bodies, but pass into the large dense masses 
of material to which I have referred as the polar caps. In later stages 
these rays are not at all fibre-like, and are continuous with the material 
which now surrounds the female nucleus. The whole appearance suggests, 
as I have said before, a flowing of material towards the female nucleus. 
But it is possible that an actual centrosome with its aster may lie concealed 
in the cytoplasm. At all events, it is evident that marked chemical and 
physical changes take place in the cytoplasm of the egg at both ends of the 
nucleus, which are later concerned with its division, and that these changes 
