628 Trow . — The K ary 0 logy of Saprolegnia. 
this division, the number of nuclei in the older oogonia would 
be doubled, since every nucleus in the oogonium undoubtedly 
passes through all the stages of division up to the halving of 
the chromosomes and the passage of the halves in pairs into 
the surrounding protoplasm. 
A study of a somewhat later stage — the typical vacuolated 
stage — shows us clearly that the conditions are not so simple. 
Fig. 11 a and b represent two sections of an oogonium, one 
tangential and the other median, the greatest diameter of 
which was 50 \x. The nuclei in this oogonium, which were 
all small, were counted carefully, and numbered forty-five. The 
oogonium probably contained at the outset, when the basal 
wall was formed, considerably over 100 nuclei : it should be 
remembered that seventy-two were counted in an oogonium 
with a diameter of 29 /x. In consequence of the division the 
number would be doubled, but the number actually determined 
was forty-five. This, in itself, would be sufficient, provided 
the case were a normal one, to prove that a larger number 
of the small nuclei must undergo degeneration. Repeated 
examinations and measurements have convinced me that the 
case is a normal one. We have, however, ocular demonstra- 
tion of the degeneration in the sections themselves ; for the 
small and badly stained chromosomes which make their 
appearance while the division is still incomplete, must be 
looked upon as more or less degenerate. There is not the 
slightest evidence for the view that the reduction is brought 
about by nuclear fusions. 
The significance of this division must, I think, be apparent 
to every one. It is exactly of the nature of a reducing division. 
The whole chromosomes are converted into half-chromosomes, 
which do not, as in the case of the direct divisions, become 
whole chromosomes by a process of growth. 
These processes correspond very closely to the karyokinetic 
phenomena described by Hartog as occurring in these plants. 
Apart from referring to the fact that the evidence for the 
occurrence of indirect division of the nucleus has been made 
more complete by my observations, I need only state that 
