242 BOTANICAL GAZETTE [OCTOBER 
In three species of Albugo there are two mitoses, in another 
species probably two, in the gametangia; while in Peronospora 
(Wager 1900) there is only one. In Sphaeroplea (Klebahn 
1899) the antheridial nuclei divide repeatedly, while the egg 
nucleus does not suffer visible change. In Vaucheria, even if 
there is a division in the oogonium, as seems possible (Olt- 
manns 1895, p. 392), it is probably not a differentiating divi- 
sion, since all of the nuclei but one wander back to the parent 
filament, and are presumably capable of vegetative function. 
From these examples it appears that the number of divisions in 
both oogenesis and spermatogenesis varies in different species, 
and differs in the two sexes of the same species; while in some 
forms there seems to be no mitosis directly concerned in the 
genesis of the female pronucleus. These conditions render 
improbable the existence of a reduction in the number of chromo- 
somes during gametogenesis in these algae and fungi. Oogene- 
sis and spermatogenesis begin almost simultaneously fora given 
pair or group of sex organs, yet all efforts to correlate their 
inception with any development external to the organs them- 
selves were vain. A comparative study of four species shows 
no constant relation between the male and female organs in the 
sequence of their development, which seems to proceed inde- 
pendently in each organ. It is not probable, as might at first 
seem, that the inception of the antheridial tube is caused by the 
presence of the oosphere, since fig. 50 presents a case where the 
antheridial tube grew and functioned normally, yet without a 
parallel development in the oogonium, or indeed the existence 
of an oosphere. 
The factor which determines how many primary oospheric 
nuclei shall enter the ooplasm is uncertain. Clearly the position 
of the nucleus during its first mitosis determines whether or not 
one of the daughter nuclei shall enter the ooplasm. Yet this 
position seems to be governed by no law, the greatest irregu- 
larity existing, as is general in cases of simultaneous division in 
multinucleate masses of cytoplasm. This irregularity is equally 
prevalent at the time of zonation (figs. 2, 28). It is quite 
