136 SEAWEEDS 
reproduction, however, the parts are reversed, since 
none is known in Bryopsis and Codiwm. 
Went,! however, in studying Codiwm tomentosum, 
found both kinds of zoosporangia on the same 
individual plants. Sometimes the small gametes do 
not appear until after the dispersal of the larger 
ones—and they may be formed from the same basal 
cell. He never observed any union of the two sorts, 
and successfully cultivated the contents of the larger 
kind of gametangia or sporangia. But it is im- 
possible to say in this case whether there had been 
conjugation or not. 
In Derbesia we have only non-sexual reproduction, 
and, if the genus be rightly placed here, this fact 
also may have its significance, since Derbesia in other 
respects strongly resembles Vaucheriacew. The 
zoosporangia arise as lateral outgrowths from the 
filaments, and contain 8—20 zoospores with a fringe 
of cilia on the anterior end. As mentioned under 
Vaucheriacee the nuclei in the parent cell become 
reduced by union to the number of zoospores formed. 
However, it is plainly an aberrant type, and needs 
further investigation. 
The Geographical Distribution Bryopsis occurs in 
all seas, but more abundantly in warmer waters. 
Codium also has an extensive range in the warm and 
temperate seas of the world. Derbesia belongs to the 
north temperate and tropical Atlantic (both Euro- 
pean and American), and occurs also on the Australian 
coasts. All three genera are British, and (with 
Vaucheria and Halicystis) constitute our represent- 
1 Vergrad. d. Ned. Botan. Vereeniging, 1889. 
