SOME PROBLEMS OF REPRODUCTION. 17 
centre. In Pelvetia six of the nuclei pass towards the 
equator of the oogonium, and two lie towards the ends of 
its axis. The cytoplasm separates into two oospheres, each 
containing one of the axial nuclei, while the six equatorial 
nuclei are left out as rejection-nuclei. Finally, in Halidrys 
and Himanthalia, and also Cystoseira, seven of the 
nuclei pass to the periphery as rejection-nuclei, while the 
eighth remains in the centre of the cytoplasm of the oogonium 
which is thus directly resolved into the single oosphere. 
Oltmanns, who gave the first correct account of these pro- 
cesses, rightly remarked on their close identity with the forma- 
tion of polar bodies in the Metazoa. It is obvious that the 
formation in Fucus is primitive, and that the advantages due 
to the increased size of the oospheres in the other genera 
are obtained by the abortion of half, three quarters, or seven 
eighths of them, and that this physiological advantage is a 
relative gain and not an absolute necessity. 
B. ApocytraL Forms. 
1. Green or Algal Types. 
CraporHora has septate filaments with many nuclei in each 
joint, and forms zoospores, ordinary or isogametal, by the reso- 
lution of these apocytia into uninucleated swarmers. In both 
cases a portion of the cytoplasm is eliminated at the bounda- 
ries of these cells, and takes no further part in the living pro- 
cesses. From Berthold’s description! it appears certain that 
he is correct in regarding this excretion of “epiplasm” as 
derived from a primitive formation of cell-wall, a process 
which has been lost in the evolution of the group. We may 
note that this confirms the propriety of our using Vuillemin’s 
term “ apocytial” instead of Sachs’ “ non-cellular.”’ 
The gametes of Cladophora are biflagellate, the ordinary 
zoospores quadriflagellate, a distinction which we interpret as 
1 Op. cit., p. 302. He expressly notes (p. 305), in opposition to Dodel- 
Port, that such formations, occurring also in asexual spore-formation, can have 
no relation to fertilisation-processes as such. 
VOL. XXXIII, PART I.—NEW SER. B 
