Trow . — The Karyology of Saprolegnia. 637 
and 21, however, illustrate sections of oogonia in successive 
stages of development, which were almost certainly those of 
»S. Thureti. They were certainly destitute of antheridia. The 
oospores are uninucleate, and exhibit those changes in the 
structure of the nucleus already described. The whole of the 
oospores in both of these oogonia, as well as a large number 
of others, were carefully studied, and every oospore proved to be 
uninucleate. A careful examination of the nucleus in Fig. 21 
will lead to the conviction that it corresponds to De Bary’s 
4 Kern-fleck,’ and that Dangeard’s view that it represents the 
first stage in the development of the fatty mass, must then 
fall to the ground. 
I had anticipated that the application of the new and 
improved method of staining with gentian-violet and eosin to 
the study of 5 . mixta would yield valuable confirmatory 
results, but have been disappointed. At the period of fertiliza- 
tion the borders of the oosphere stain deeply with gentian- 
violet, and numerous small deeply stained granules appear in 
the protoplasm, so that the critical stages, as to which con- 
firmation was needed, were more or less obscured. A return 
to the earlier method of staining with acetic carmine produced 
better preparations, but even these were not sufficiently good 
to give unquestionable results. When the young oospore has 
developed a little, and the nuclei in particular have increased 
in size, we find that many of the oospores are binucleate , as 
represented in Fig. 22, while others are uninucleate . 
A long study of this perplexing condition, involving the 
careful examination of hundreds of oospores, has led me to 
the conclusion that the development in the uninucleate forms 
is apogamous, that is to say, no fertilization takes place ; 
while in the binucleate forms fertilization occurs, and the 
nuclei are respectively male and female. This conclusion is 
based solely upon the absence of all evidence for either the 
fusion or division of the nuclei in the young oospore, and the 
important fact that the gameto-nuclei — as I must term them — 
may be found close together, though still distinct, in oospores 
much older than those which contain a single nucleus. 
