267 
of Peronospora parasitica. 
and P. effusa he shows a state of fusion in which the fusing 
nuclei are similar to those in Ascaris , in which the fusion 
takes place in the chromosome stage, and the chromosomes 
are visible before fusion; and he refers generally to the 
process of fertilization in the following words as if it referred 
to the whole group: ‘ Auch die Chromosomen werden gut 
sichtbar, und ich konnte auch im Spermakern 12-16 derselben 
nachweisen; die Kernmembran verschwindet allmahlich und 
es beginnt die Verschmelzung der beiden Kerne. . . . Es 
geht mit Sicherheit aus meinen Untersuchungen hervor, dass 
der embryonale Kern aus einer Zahl von Chromosomen 
zusammengesetzt ist, die um die Halfte grosser ist als die 
Zahl der Chromosomen, welche in einem jeden der beiden 
Geschlechtskerne, die ihn zusammensetzen, nachweisbar ist, 
und dass dieselben vor der Befruchtung gar keine Reduction 
zeigen.’ 
With this exception, however, Berlese and I are in agree¬ 
ment as to the essential facts of fertilization in Cystopus, and 
it now remained for me to determine whether my former 
observations on P. parasitica 1 —that the formation of the 
female or oosphere-nucleus takes place by the fusion of two 
or more periplasmic nuclei, and that the ripe oospore is 
uninucleate—were correct, or whether the facts are in accord 
with the more recent observations of Berlese on Peronospora , 
and especially with his statement that the ripe oospore of 
P. parasitica is multinucleate 2 . I found on reinvestigation 
that the process of fertilization is similar in its essential 
features to that which takes place in C. Candidas , but that, 
unlike all the other species of Peronospora and Cystopus 
which have so far been examined, the ripe zygote is uni¬ 
nucleate. 
Stevens 3 has recently published an account of the fertiliza¬ 
tion in Cystopus (Albugo ) Bliti , which differs entirely in its 
essential details from that described by Berlese and myself for 
other members of the group. The oogonium and antheridium 
1 Annals of Botany, vol. iv, Nov,, 1889. 
2 Berlese, loc. cit. p, 181. 3 loc. cit. 
