28 I 
Cytology of Pythhim ultimum, n. sp . 
This slow movement may last for from one to two hours 
according to De Bary. In Fig. 4 g two granules are repre- 
sented in the fertilization-tube. They slowly passed on down 
the tube and necessarily disappeared from sight before they 
reached its end, that being concealed from view. In Fig. 4 h y 
the progress made in the emptying of the antheridium is 
scarcely noticeable, while in Fig. 4 j\ drawn half an hour 
later, it is practically completed. The actual process of 
fertilization may have taken place at any time between 
1.0 p.m. and 2.0 p.m. It almost certainly takes place quickly. 
What the significance of the gradual emptying may be it is 
difficult to say. Some evidence has been collected to show 
that much of the antheridial contents pass into the periplasm. 
On three occasions a little mound of protoplasm collected 
around the indentation made by the fertilization-tube and 
streamed away over the central mass from that point. It is 
significant that the egg rounds itself off and appears covered 
with a membrane before the last traces of protoplasm leave 
the antheridium. The last visible particles, as in Fig. 4 j, do 
not pass out as such. They appear to be dissolved in situ , 
and so slowly vanish. 
Observations on the living material do not suffice to prove 
the existence of fertilization, much less the mode in which it 
is effected. We have in fact the usual difficulty to contend 
with, the large female gamete is too dense to allow us to 
watch the entry of the small male gamete. It seems abun- 
dantly clear, however, that we have no justification for recog- 
nizing a differentiation of the contents of the antheridium 
into gonoplasm and periplasm. A study of stained sections 
is absolutely necessary for the proper interpretation of the 
phenomena observed in living material. 
Maturation of the oospores. The maturation of the 
oospores may be completed in about twenty-four hours after 
fertilization has taken place. Three points of interest have 
to be noted. The original thin membrane covering the young 
oospore increases considerably in thickness by the deposit on 
the inside of a thick layer of some kind of cellulose. The 
