The observations of Moller, &c., on the germination cannot be assumed to negative the sexual hypothesis for the sexual cells of Ulothrix and Ectocarpus, for example From Strasburger's Lehrbuch der Botanik, by permission of Gustav Fischer.
Bornet, however, called attention in 1871 to the fact that two kinds of plurilocular sporangia occurred in certain species of the genus Ectocarpus - somewhat transparent organs of an orange tint producing small zoospores, and also more opaque organs of a darker colour producing relatively larger zoospores.
Buffham, Batters in 1892 separated the three species, Ectocarpus secundus, E.
The conjugation of similar gametes, arising from distinct plurilocular sporangia, was observed by Berthold in Ectocarpus siliculosus and Scytosiphon lomentarius in 1880; and these observations have been recently confirmed in the case of the former species by Sauvageau, and in the case of the latter by Kuckuck.
The four species - Ectocarpus siliculosus, Giffordia secunda, Cutleria multifida and Haplospora globosa - may be taken to represent, within the Phaeosporeae, successive steps in the advance from isogamy to oogamy.