KING: CYTOLOGY OF ARAIOSPORA PULCHRA. 
225 
Wager (:00) has shown in Peronospora parasitica that just 
before the periplasm is cut off from the oosphere, a nucleus is drawn 
into the latter. The attraction of the central body for the nucleus 
is indicated by the fact that the anterior portion of the latter, as it 
passes through the ooplasm, is drawn out toward the body. He 
further observed nuclei out in the periplasm that had put out beaks 
in the direction of the central body. Stevens (:01b) finds several 
female nuclei drawn out toward the coenocentrum in at least two 
members of the genus Albugo. Wager, Trow, and Stevens all agree 
that the central structure attracts the sperm nucleus, and all figure 
sperm nuclei elongated in the direction of the attractive center. 
Stevens (:01b) further suggests that in Albugo tragopogonis and 
Albugo Candida it also “ serves as a source of nourishment for the 
surviving female nucleus.” 
In Araiospora there is evidence that the central mass of ooplasm 
is an agent in bringing the nuclei together. 
The writer did not observe either male or female nucleus in tran¬ 
sit through the peripheral ooplasm ; this is possibly due to the fact 
that the latter is extremely coarse meshed and, in consequence, 
offers little resistance to a moving body. It is not known, there¬ 
fore, whether or not they put out beaks toward the central mass as 
they approach it. Neither is it known precisely when they enter. 
Certainly, in many cases, the central ooplasm does not contain a 
nucleus until just before the periplasm is formed and it is equally 
evident that there is one present just after the oosphere is differen¬ 
tiated. In this connection figure 19 (plate 13) represents an inter¬ 
esting stage ; in this figure a male nucleus is embedded in the fine 
meshed center. The next section shows a female nucleus some 
distance to the right of the position occupied by the male nucleus. 
The latter has a slight beak put out in the direction of the female 
nucleus. The fact that to reach the female nucleus, it must now 
move practically at right angles to its previous direction of motion, 
suggests strongly that mutual nuclear attraction is of little or no 
consequence in bringing the sperm from the antheridium. Cer¬ 
tainly, if it were an important factor the sperm nucleus would move 
directly toward the female nucleus. The same thing is shown in 
figure 21 (plate 13) and figure 35 (plate 15) where two nuclei both 
in the plane of this section, seem to be strongly attracted to each 
other; no antheridium appears in the section, which would suggest 
