The oogonia arise on a stalk cell from the lining layer of the cavity, the contents dividing to form eight oospheres as in Fucus, four as in Ascophyllum, two as in Pelvetia, or one only as in Halidrys.
It would seem that eight nuclei primarily arise in all Fucaceae, and that a number corresponding to the number of oospheres subsequently formed is reserved, the restbeing discharged to the periphery, where they may be detected at a late stage.
On the maturation of the oospheres the outer layer of the oogonial wall ruptures, and the oospheres, still surrounded by a middle and inner layer, pass out through the mouth of the conceptacle.
Then usually these layers successively give way, and the spherical naked oospheres float free in the water.
The antherozoids are attracted to the oospheres, round each of which they swarm in great numbers.