306 BOTANICAL GAZETTE [MAY 
In the Mucorales all that we can safely affirm now is the 
fusion of two multinucleate masses of protoplasm. The history 
and fate of the nuclei is certainly not clearly understood, but the 
indications are rather for some complex phenomenon involving 
many nuclei than a simple act of fertilization, concerned with 
only two sexual nuclei. . 
The Peronosporales present two well defined conditions at 
the time of fertilization. The phenomenon in A. d/i# is at vari- 
ance with that established for A. candida, and indicated by super- 
ficial examination for several other forms. In A. candida the 
sexual act is the fusion of two nuclei, thus satisfying the require- 
ments generally understood by fertilization. In A. dt there are 
many sexual nuclei fusing in pairs, about 100 sperm nuclei enter- 
ing a compound oosphere which contains approximately 100 
female nuclei. 
What are the homologies between these two species? The 
oogonia and antheridia are certainly homologous structures, and 
there is no evidence that the nuclei contained within are not 
likewise. There seems indeed, from the cytological data at 
hand, good reason to believe that these nuclei are all homolo- 
gous, both those that fuse and those that remain sexually inac- 
tive, either left behind in the antheridium or lying in the periplasm 
of the oogonium. Our inability at present to distinguish 
between the various mitoses in either sexual organ offers the 
strongest evidence of the position above taken. The difference 
between these two species is perhaps then only one of the num- 
ber of the nuclei that are actually sexual or gametes in the 
strictest morphological sense. Nuclei that are not actually sex- 
ual, either in the antheridium or periplasm of the oogonium, may 
stand phylogenetically for a previous condition, when these 
ofgans contained a much larger number of sexual nuclei. This 
point of view seems to have been in the mind of Hartog (91): 
The antheridium and oogonium of Albugo are gametang!4- 
However remarkable is the difference between A. candida and 
A. biti it is nevertheless merely a question of the number of 
nuclei that become sexually functional or active gametes. In . 
