290 Trow . — Observations on the Biology and 
distribution is by no means uniform. The oogonium has no 
central vacuole at any stage in its development. 
In Fig. 7 the oogonium is completely formed, its basal wall 
being already present. The protoplasm is coarsely reticulate. 
The nuclei are relatively large and have arranged themselves 
at the periphery of a hollow sphere. This increase in size 
of the nuclei is in preparation for an indirect division. The 
arrangement of the nuclei in a ring prefigures the division of 
the contents of the oogonium into oosphere and periplasm. 
In another oogonium in the same stage of development, which 
had a diameter of 18/x, the nuclei were counted in the three 
sections. The numbers were ten, three, and one, making a 
total of fourteen. 
In Fig. 8 the antheridium is shown in contact with the 
lateral wall of the oogonium. A ‘ receptive spot ’ has been 
formed by the oogonial plasm, somewhat similar to, although 
perhaps not so highly differentiated as those described by 
Wager (’ 96 , ’ 00 ) in Cystopus and Peronospora , and Stevens 
(’ 99 ) and Davis (’00) in Albugo (Cystopus) Bliti and Albugo 
(Cystopus) Candida . A small nucleolus is visible in the oogonial 
nuclei at this stage. 
In Fig. 9 the formation of the egg has commenced, the 
fertilization-tube is in contact with the dense protoplasm, 
and the ring-like grouping of the nuclei is very noticeable. 
The nuclei are in metaphase, the spindles being plainly seen 
in the oogonium and antheridium. One oogonial nucleus is 
inside the ring formed by the others. The number of separate 
chromosomes visible in a polar view of one of the dividing 
nuclei is 8. 
In Fig. 10 the nuclei are in anaphase, and the connecting 
threads of the achromatic figure are clearly visible. The egg 
is outlined, and one nucleus only is dividing inside it ; the rest 
are in contact with its outer surface. 
In Fig. 11 the fertilization-tube has penetrated the periplasm 
quite far enough for its apex to be invisible, except with the 
aid of sections. Here two nuclei are still in the egg, and 
. nuclear division is not so far advanced as in Fig. 9, although 
