664 Miyake . — The Fertilization of 
contents of the oogonium differentiate into the ooplasm and 
periplasm. Then one nucleus from the periphery enters into 
the ooplasm to become the functional female nucleus of the 
oosphere, while all the other nuclei in the periplasm degenerate 
there. 
6. The nuclei of the antheridium after division degenerate, 
except one which remains to become the functional male 
nucleus. While the formation of the oosphere is taking place 
in the oogonium, the antheridium sends out a fertilization- 
tube. The tube reaches to the oosphere, piercing through 
the wall of the oogonium and periplasm. 
7. The greater part of the contents of the antheridium, 
including the male nucleus, passes gradually into the oosphere, 
through the fertilization-tube. The male nucleus finally comes 
in contact with the female nucleus, and they fuse together to 
form the nucleus of the oospore. 
8. After the discharge of the antheridial contents into the 
oosphere, the exospore begins to form around the latter. The 
greater part of the periplasm seems to be used in the formation 
of the exospore which has about the same thickness as the 
oogonium-wall, when completed. A much thicker endospore 
develops later inside the exospore. The ripe oospore is uni- 
nucleate, and in the stained section several chromosome-like 
granules are visible in the nucleus. 
Cornell University, 
June , 1901. 
After this was written, Dr. T row’s paper, ‘Observation on 
the Biology and Cytology of Pythium ultimum , n.sp.,’ appeared 
in Annals of Botany (June, 1901). His results agree with 
mine in essential points, but differ somewhat in matters of 
less importance. 
