1900] FERTILIZATION OF ALBUGO CANDIDA 299 
gradual accumulation of the protoplasm at the center of the 
oogonium. The nuclei, very variable in number (Wager esti- 
mates from 70-110), are at first in the resting condition, but 
very soon prepare for and pass through a mitosis. They lie in 
a coarsely vacuolate cytoplasm, 
The first stage in the differentiation of the oosphere is illus- 
trated in fig. z, which shows a slight but not conspicuous 
increase in the granular protoplasm at the center of the oogo- 
nium. . There soon appears, however, a remarkable structure in 
this region of denser protoplasm. It develops form — organiza- 
tion, and finally becomes avery prominentelementint 
Mr. Stevens found a similar body in A. d4t, appearing at this — 
period in ontogeny, and believing it to be associated with pass ea 
tant activities in the oogonium called it the “ coenocentrum.’ 
The coenocentrum of A. candida is very much larger than 
that of A. dit, and has attracted the attention of several 
observers. Wager was the first to recognize its protoplasmic 
nature, which appears unquestionable through its structure, 
development, and reaction to stains and clearing agents. When 
fully differentiated the coenocentrum is a sphere of dense, 
deeply-staining, slightly granular protoplasm, entirely free from 
inclusions, and two to four times the diameter of the nuclei. It 
is Sometimes surrounded by a zone of lightly staining protoplasm, 
as is shown in jig. 2, through which delicate radiations may be 
traced. The coenocentrum develops, as has been said, from 
an accumulation of protoplasm in the center of the oogonium 
fg. 1). It reaches its most beautiful state of differentiation 
when the appearance is that presented by fig. 2. Later the 
Structure contracts somewhat, rounds itself off, and becomes a 
very dense body with a firm outline, as is indicated in figs. 3-6. 
It is then very conspicuous, staining deeply, but is not so plainly 
related to the cytoplasm as in earlier stages. Certain investi- 
gators have mistaken these later conditions for accumulations of 
oil or similar matter. 
The differentiation of the oosphere, that is the separation of 
the ooplasm from the surrounding periplasm, is heralded by the 
