238 Rickett.—Fertilization in Sphaerocarpos. 
Seco7id Phase. 
The next phase is marked by a change in shape of the male nucleus, 
which now becomes ovoid. This is shown in Fig. 3 . Its structure and 
position do not change. It is of this form for about eight hours. It becomes 
somewhat shorter, being now about 5 y in length ; but its thickness almost 
equals its length, so that it is evident that a considerable enlargement has 
taken place. 
The female nucleus is the same in appearance as in preceding and 
succeeding phases (Figs. 4 and 5 ). The egg cytoplasm is also unchanged 
in many cases, but in others it becomes coarser, showing a deeply staining, 
irregular reticulum. This is formed of threads of varying thickness, some¬ 
times straight, sometimes very much twisted and curved, with granules of 
very various sizes at the points of junction of the threads and often at other 
points along them. This condition is more usual in succeeding phases, and 
is illustrated in Fig. 8 , which represents the fourth phase. Such a structure 
may, of course, be considered as an alveolar one, greatly distorted by the 
fixing agent. My chief reasons for considering it a true reticulum are that 
a very clear alveolar structure is to be seen in later stages, and that eggs at 
this stage, though fixed in the same way, present quite a different appearance. 
Third Phase. 
During the next twelve hours, the male nucleus is approximately 
spherical (Fig. 4 ), and sometimes has the appearance of a dense mass of 
granules rather than that of an absolutely homogeneous body as heretofore. 
This structure may be especially evident at its surface, which is often rough, 
with tiny protrusions, instead of having a clear smooth outline. In most 
cases, however, the structure of the male nucleus is apparently the same as 
in the previous stages, except that the clear space surrounding it is now for 
the first time bounded by a definite membrane. This membrane is con¬ 
tinuous with the cytoplasmic reticulum and is probably cytoplasmic in 
origin. The male gamete is now, therefore, represented in the egg by 
a typical nucleus, consisting of a nuclear membrane, a dense central mass 
containing chromatin, and a clear material filling the rest of the nuclear 
cavity; this clear material is analogous to the nuclear sap of the ordinary 
vegetative nucleus, and is probably formed by extrusion from the denser 
central mass of the nucleus. 
The egg retains the same appearance as in the previous phases, as to 
both its nucleus and its cytoplasm (Figs. 4 and 5 ). Its surface has lost that 
‘ frayed 5 appearance characteristic of the earliest stages, and a clearly defined 
membrane is present. Without microchemical tests, it is impossible to say 
whether or not a cell wall is present. In all later stages, and even in the 
young embryo consisting of several cells, there is no thicker boundary of the 
