222 Barrett. — Development and Sexuality of some 
to the opposite wall of the antheridium after most of the contents had passed 
over. Very rarely does any protoplasm remain in the male cell after 
fertilization. 
Before the movement of the protoplasm of the antheridium into the 
oogonium begins, one only rarely detects a communicating pore. In fact, 
in many cases, it cannot be detected even while the passage of the proto- 
plasm is going on. The pore in the fused wall is small and soon closes by 
growth of the surrounding wall, apparently after the act of fertilization is 
completed. Owing to the thick encrustation on the oogonial wall, together 
with the coarsely granular protoplasm, I have been unable to see the 
movement of the male protoplasm after it has passed through the com- 
municating pore. 
As a result of fertilization the oospore forms about itself a wall in close 
contact with that of the oogonium. This wall rapidly thickens and serves 
to protect its contents against unfavourable external conditions (Fig. 21). 
The now empty antheridial wall may persist for some time in its normal 
shape, but eventually becomes more or less collapsed. 
When more than one antheridial cell is attached to an oogonium there 
is no apparent difference in their behaviour other than that their contents may 
or may not simultaneously pass into the female cell. Although one usually 
finds that the movement has at least started in all male cells before any 
one is entirely emptied, exceptions to this have been observed. 
In the case of the sexual spores of the other two species, O. Saprolegniae 
and O . luxurious , what is said of one will apply equally well to the other. 
Those individuals which are to give rise to sexual cells can be detected early 
in their course of development by the difference in the appearance of their 
protoplasm from that of the young sporangial cells, and by the close 
association of the two or more individuals. This early condition is not so 
easily detected, however, as in the case of O. vexans. 
The protoplasm of both the male and female individuals is much 
vacuolated and somewhat coarsely granular. The limits of the cells are 
less clearly defined than those of O. vexans because of the closer resemblance 
of the protoplasm to that of the host (Figs. 24, 83). Later their individuality 
and form is much more marked, as their protoplasm becomes more differ- 
entiated than that of the host (Figs. 25, 84, 85). The oogonium contains 
large vacuoles surrounded by more or less granular protoplasm, while that 
of the antheridium is finely granular and homogeneous. At this stage 
walls have formed, and there is observed a pronounced clear zone of proto- 
plasm about the oogonium, which exhibits a strong contrast to the dense 
granular layer of the host on which it abuts. Dangeard (7) calls attention 
to this zone in the resting spores of Olpidiopsis ( Pseudolp idiu m ) Saprolegniae , 
Cornu, as interfering with his observations of the nuclei. 
The host protoplasm beyond this layer forms a complicated system of 
