546 Trow . — On Fertilization in the Saprolegnieae . 
the sexual organs, that of the fate of the supernumerary nuclei in the 
oogonium, had not been very successfully attacked during the course of 
these investigations. My view that the supernumerary nuclei disappeared 
by a process of digestion and absorption was distinctly opposed to that 
held by both Hartog and Humphrey. 
The difficulty of following the process of degeneration of the nuclei in 
detail was so great that I determined to study a member of the Perono- 
sporeae with a view to getting some practice in following the degeneration 
of indubitable superfluous nuclei. With this end in view a special study 
of a species of Pythium was made in the years 1899 and 1900. It 
was very gratifying to find that with the same methods as had been 
employed in the case of the Saprolegnieae, practically the same results 
were obtained ; in particular it was easy to trace exactly the same 
succession as regards the number of nuclei in the reproductive organs. 
Moreover, it became apparent that chromacetic acid was an excellent 
fixing reagent for use in this group of plants. 
With the knowledge gained by these investigations a fresh start 
was made in the study of the Saprolegnieae in 1902. The first suitable 
species isolated, which was collected for me by one of my pupils, 
Mr. Pole-Evans, proved to be Achlya polycindj'a , Hildebrand. I had 
already spent twelve months upon the investigation of this and practically 
completed my work when Davis (’ 03 ) published his interesting obser- 
vations on the cytology of the oogonia in an apandrous species of 
Saprolegnia. This well-known cytologist fully confirms the observations 
already made by me in that genus, and delineates with characteristic care 
and diagrammatic clearness the details of nuclear structure. The great 
merit of the research from the cytological point of view rests on the 
discovery of a structure which the author classes as a ‘ coenocentrum,’ but 
which has all the appearances of a centrosome and its astrosphere. 
Although this structure has not, in my opinion, the significance which 
Davis attaches to it, yet it may be conceded that its presence materially 
helps the observer to clear up the difficulties inherent to the study of the 
nuclei in these sexual organs. Unfortunately, its discoverer made 
comparatively little use of his opportunity, although he seems to have been 
fully aware of it. Davis’s paper is mainly occupied with theoretical 
discussions of a highly controversial character. The author rejects 
Hartog’s observations as to wholesale fusions of nuclei, and adopts the 
theory first promulgated by me, that the supernumerary nuclei are 
digested and absorbed by the ooplasm. As already noted above, 
however, he refuses, with very marked emphasis, to accept my observa- 
tions and conclusions as to fertilization, although, strangely enough, they 
are, so far as the observations are concerned, perfectly consistent with his 
own. His reason for this somewhat singular attitude of mind appears to be 
