236 Rickett.—Fertilization in Sphaerocarpos. 
determined. Neither at this nor at any later stage could I discern anything 
in the egg cytoplasm that might be interpreted as the remains of the cyto¬ 
plasm of the antherozoid ; yet it is certain that the rod-shaped body just 
described becomes transformed into a typical nucleus. Probably the cyto¬ 
plasmic portions of the antherozoid are absorbed by the egg cytoplasm 
immediately after its penetration. Possibly the clear space mentioned 
above is occasioned by the occurrence of this change, though it seems more 
probable, in view of later changes, that it is due to an extrusion of material 
from the dense body itself. Taking what seems to be the most probable 
view of the origin of the latter body, I shall refer to it in future as the 
antherozoid nucleus, or as the male nucleus. A comparison of its dimen¬ 
sions with those of the free-swimming antherozoid shows that it has con¬ 
tracted greatly in length, while increasing in thickness. 
In one case (one and a half hours after flooding), the male nucleus was 
not surrounded by a clear space, and was slightly more slender than usual. 
This is the only indication found of what must be an early stage in an 
extremely rapid process—the transformation of the antherozoid, or of its 
nucleus, into a large, dense, rod-shaped body. Indeed, the rapidity of all 
these first processes and changes is impressive. One case in which the 
male nucleus was already clearly distinguished in the usual shortened form 
was found forty-five minutes after flooding. The absence of clear stages 
showing the penetration of the antherozoid is no doubt partly due to the 
rapidity with which it takes place. 
In another case (one and a half hours after flooding) the egg cytoplasm 
shows a slight depression in its surface, near one end of the male nucleus, 
which now lies within. This probably marks the place where the antherozoid 
entered the egg. 
The egg at this time shows little change from the condition already 
described. The cytoplasm varies in appearance. In some preparations it 
has the appearance of a fine, complex reticulum embedded in a homogeneous 
mass (Fig. 2 ). This apparently reticular structure may of course be in 
reality alveolar. An alveolar structure does indeed appear in later stages; 
but in these cases the open spaces are large, regular in shape, and clear, 
whereas at the early stage now under discussion they are small, irregular, 
and take a deep stain. It seems probable, therefore, that the structure here 
is reticular in nature, with a dense homogeneous ground substance. Even 
at this early stage, the cytoplasm of different parts of the egg may vary 
in structure. In one case, the cytoplasm is noticeably denser about the 
nucleus, and shows a more open structure in the peripheral region. This is 
suggestive of what is to come later. A similar structure has been described 
by several authors. Gayet (1897) says that the egg of Sphagnum is formed 
of cytoplasm having a reticular structure, the meshes of which are denser 
about the nucleus. Campbell (1918) figures and describes the ripe egg of 
