; 
} 
| 
1900 | FERTILIZATION OF ALBUGO CANDIDA 309 
The bearing of such possibilities as have been considered 
above upon the phylogeny of the Phycomycetes is of course 
attractive, but hardly within the range of the present discussion 
It may be questioned whether the theoretical consideration 
of and speculation upon such difficult subjects as these we have 
so briefly outlined is worth while. Certainly we have few or no 
facts to warrant the expression of positive opinions, yet attempts 
to understand clearly and explain even the most obscure subjects 
may suggest methods of approach to others working for the 
same ends, and such hopes must be their justification. 
SUMMARY. 
Communication between the oogonium and antheridium is 
established by a papilla from the former structure, which works 
its way through the cellulose walls into the antheridium. 
The differentiation of the ooplasm is associated with the 
appearance of an organized spherical protoplasmic body in the 
center of the ocogonium. This structure has been named the 
coenocentrum (Stevens, 99). 
A conspicuous stage in oogenesis is that called zonation. 
Then the nuclei, usually in mitosis, lie at or near the inner 
boundary of the periplasm, and the coenocentrum is very promi- 
nent in the center of the ooplasm. 
The oosphere is organized after the stage of zonation, when 
one of the nuclei from near the periphery returns to the interior 
of the ooplasm, and takes a position close to the coenocentrum. 
There is one mitosis in the oogonium, which occurs usually at 
or slightly before the time of zonation. There is no proof that 
this mitosis is a reducing division. The spindle is intranuclear, 
and the nuclear membrane persists until late anaphase. It wae 
not possible to establish the presence of centrosomes, possibly 
because the mitotic figure is very small. The number of chromo- 
Somes is probably 12 to 16 (Wager’s estimate). 
he oosphere of A. candida is certainly generally, if “he uni- 
versally, uninucleate. This point was studied with especial care, 
in view of the conditions described by Mr. Stevens (99) in A. bliti. 
