go BOTANICAL GAZETTE 
known principles of sexual evolution which the author has recent! 
discussed (Popular Science Monthly, February 1903, p. 300). Th 
tangium produced numerous gametes which were undoubtedly m 
‘since the sperms of Vaucheria are biciliate and the Siphonales rn 
follow exactly the steps through which the ancestors of Vauche 
passed in their evolution from isogamy, because it is the only h 
ogamous type in the order, and there are few connecting links Ww 
the prevailing simple conditions among the Siphonales. However, 
we have in Bryopsis a form whose gametes, although both motile 
are of different sizes, those of the female being much larger and 
developed less numerously in the gametangium. This type exhib 
the first step toward the condition of heterogamy, but we do 
know exactly what would follow next. Probably the protop. 
cleavage in the female gametangium would become gradually redi 
and fewer gametes formed, until finally there would be no more clea 
age, all of the protoplasm going into a single gamete, which wh 
non-motile would become the solitary egg (Vaucheria). This 
centration of protoplasm for a lessened number of gametes or 
single egg must be accompanied by nuclear degeneration @/ the at 
tral gametangium were multinucleate. ‘There are of course types. 
gametangia among the algae which are uninucleate from the 
ning, and there cannot be any nuclear degeneration in these. 
the multinucleate gametangium is not uncommon in certain | 
and is apparently universally present in the Siphonales. 
It is possible that Sphaeroplea will be found to represent ¢ 
in sexual evolution intermediate between Bryopsis and Vauc 
without necessarily implying a relationship to these types. Kle 
(99) and Golenkin (’99) have given us the most complete acc¢ 
Oogonesis in Sphaeroplea. Klebahn found the eggs of S. 
Braunii to contain several nuclei (2-5), one of which beca! 
functional female gamete nucleus; the others remained ini : 
might be found in the ripe spore. It becomes an interesting 
Whether or not these would eventually degenerate. This: 
Sphaeroplea may illustrate the beginning of a process. 
