564 Trow . — On Fertilization in the Saprolegnieae. 
Two simple anomalies which came under observation in this species are, 
however, worthy of mention. In the case of one oospore — represented in 
Fig. 33 — which contained a typical ovocentrum, an astrosphere and female 
nucleus, two sperm-nuclei had entered the oosphere through the fertilization- 
tube, and commenced to form astrospheres. The other oospores in the 
oogonium were normally fertilized. The fate of such sperm-nuclei is, of 
course, not ascertainable. 
In one oogonium, containing about a dozen oospheres, three had the 
structure represented in Fig. 34. The impression given was that of two 
oospheres which had fused together, the line of fusion being indicated by 
the marginal indentations and the arrangement of the vacuoles in the plane 
connecting these. The nuclei, astrospheres, and ovocentra were well 
developed, and the mutual repulsion of these was very obvious. Such a 
case as this allows one to infer with some confidence that the size of the 
oosphere and the attracting (or repelling) forces associated with the nucleus 
and astrosphere stand in some definite quantitative relation to one another. 
The remaining oospheres in this oogonium were relatively small, but each 
had otherwise the normal structure. Although about thirty generations 
of cultures were examined in the fresh condition during the investigations 
made on this species, I never saw an oogonium with anomalous ripe 
oospores such as might be expected to result from the fertilization of 
such oospheres as these. It is upon such anomalous binucleate oospheres 
that Davis (’ 03 ) founds some of his most important conclusions. It 
would be useless to discuss these here. A theory founded upon ex- 
ceptions and anomalies may be sound enough, but the exceptional 
facts recorded by Davis admit of a simple explanation, and certainly 
do not appear to have the phylogenetic significance which he attributes 
to them. 
Summary of the evidence as to the occurrence of fertilization in the 
Saprolegnieae. In view of the facts recorded above, we may safely affirm 
that a normal fertilization takes place in Achlya De Baryana. For it has 
been shown that (1) the oosphere is uninucleate, the young oospore binu- 
cleate, and the old oospore uninucleate — the formula showing the number 
of nuclei in the reproductive organs is 1, 2, 1 ; (2) the protoplasm of the 
fertilization-tube becomes continuous with the ooplasm of the oosphere ; 
(3) the entry into the oosphere of a sperm-nucleus can be traced ; (4) the 
sperm-nucleus becomes associated with a special centrosome and astro- 
sphere ; and (5) the male and female nuclei fuse to form one zygote- 
nucleus. To Achlya De Baryana we may add, on the basis of my own 
earlier observations, fully concordant with the later ones so far as they 
go, four distinct species. The formulae as to the succession of the nuclei 
has been determined in these, and the cytological features are consistent 
throughout. The later results are, however, naturally more complete than 
