562 Trow. — On Fertilization in the Saprolegnieae. 
The study of their fate has been practically a failure. They, in fact, soon 
disappear, and the mode in which this takes place has still to be determined. 
The ovocentra gradually disappear too, being however still clearly visible 
when all traces of the astrospheres have vanished (Fig. 30). The male and 
female nuclei increase in size and capacity for staining during this period, 
are easily demonstrable, and are always found in close proximity to 
each other near the centre of the oospore. When the ovocentra have 
finally disappeared, the gameto-nuclei may be found either close together 
or at a considerable distance apart, and frequently at some distance from 
the centre of the oospore (Fig. 31). In view of these phenomena it seems 
useless to discuss Boveri’s theory of the function of the centrosome in 
fertilization. At any rate, it is only necessary to state that the fusion of the 
gameto-nuclei is delayed for at least twenty-four hours, and that the 
division of the zygote-nucleus may not take place for months. 
It is, however, worthy of note that the nuclei at this stage are easily fixed 
and stained. Binucleate oospores representing this stage would be, in fact, 
the most obvious structures in moderately good preparations. This must 
be the stage which Humphrey and Hartog saw and figured as representing 
the last of the nuclear fusions assumed by them to take place in the 
oogonium and oospheres. I examined critically three oogonia containing 
respectively fourteen, thirteen, and fifteen oospores, and all were binucleate. 
Thousands of sections of oospores must have been casually observed in this 
condition whilst searching for other stages, and they were always binucleate 
or uninucleate. If uninucleate, one could confidently predict that an 
adjacent section would be likewise uninucleate. The binucleate character 
of isolated oospores has often been proved in this way. It is only after 
repeated experiences of this kind that one becomes confident that uninu- 
cleate sections always go in pairs. 
This stage in development is, of course, preceded by one in which 
fertilization is going on, and if attention be directed specially to it, and the 
oogonia are carefully examined, we find that fertilized and unfertilized 
oospheres occur together in the same oogonium. We see, side by side, 
genuinely uninucleate and binucleate eggs, not simply uninucleate and 
binucleate sections. Such a condition of affairs depends upon the obvious 
fact that the fertilization of the numerous oospheres is not affected simul- 
taneously. Three oogonia in this condition were examined critically. 
No. 1 possessed eight uninucleate oospheres and two binucleate oospores ; 
No. 2 possessed one uninucleate oosphere and six binucleate oospores ; 
No. 3 possessed six uninucleate oospheres and two binucleate oospores. 
During the maturation of the oospores the oospore-wall thickens and 
granules of reserve material collect in the protoplasm. It is only when 
these processes are well under way that the fusion of the gameto-nuclei 
takes place. A remarkable feature of this stage is that the chromosomes 
