24 MARCUS M. HARTOG. 
mantle around the central space. The protoplasm then becomes 
aggregated into distinct masses, the oospore “ origins,” pro- 
jecting into the vacuole and united by a continuous peripheral 
mantle, which thins gradually as its substance becomes taken 
up into these masses. Finally, the connecting mantle gives 
way ; the masses separate and round off; after a short rest 
they become ameeboid, and some of their blunt, non-nucleated 
processes become abstricted. Very soon, however, they are 
taken up again by the masses which abstricted them, and 
these masses round off into the ‘‘ oospores.” The very same 
abstriction and resumption of non-nucleated processes of cyto- 
plasm takes place in the formation of the asexual zoospores ;} 
it is probably a process derived from cell-wall formation, 
analogous to what we have seen in Cladophora, but in a 
yet more reduced condition. The oospores after coming to 
rest soon become surrounded by a cellulose wall, thickened by 
successive internal deposits; each finally possesses a single 
nucleus in the resting state, i.e. spherical, with a single 
central sphere of chromatin. The complete fusion of the 
nuclei takes place in Saprolegnia as early as the first forma- 
tion of the masses or oospore origins, while in Achlya it may 
be deferred till after the formation of the spore membrane, 
for young oospores are frequently binucleate. 
The antheridium is also multinucleate, and lies closely 
appressed to the oogonium; on the rupture of the proto- 
plastic mantle of the oogonium and separation of the oospores 
it emits tubes which grow into the cavity of the oogonium, 
and abut against the oospores just before they form a cell-wall 
or during this process; but they do not enter the oospore, 
open, or emit any fertilising bodies.” Their contents are 
1 See Rothert, ‘‘ Entwicklung d. Sporangien bei den Saprolegnieen,” 
1888 (this paper was an advance publication of ‘Cohn’s Beitrage,’ vol. v, 
1890; it was abstracted and criticised by me under the title “ Recent Re- 
searches on the Saprolegniex,”’ in ‘ Annals of Bot.,’ vol. 11, 1888. 
2 T have now fully satisfied myself that the contrary statements of Prings- 
heim (in ‘Sitzungsber. d. Berl. Akad.,’? 1882) are erroneous, being based 
partly on the intrusion of parasites as shown by Zopf, partly on the post- 
mortem appearances produced by unsuitable reagents, 
