486 Davis . — The Origin of the Archegonium. 
be noted, and then we shall be ready to consider it in relation 
to our problem of the origin of the archegonium. The zoo- 
spores or gametes from plurilocular sporangia escape in 
various ways. There is extensive dissolution of the walls 
forming the compartments, and the zoospores are in this 
manner set free. But it has been observed in some species 
that the zoospores make their exit from the tip of the struc- 
ture. It seems that the walls in the interior of the sporangium 
may break down more rapidly than those on the outside, so 
that the zoospores come to lie almost free in the interior, and 
are therefore able to escape from the opening first formed, 
which is generally at the tip. 
We shall now take up some speculations on the fate of 
such a structure as the plurilocular sporangium under certain 
environmental conditions and in relation to the principles of 
sexual evolution. We shall try to show that the archegonium 
and antheridium might have been derived from such a 
structure. 
It should be clearly understood that this is not stating 
a belief that the Phaeophyceae were the progenitors of the 
Bryophytes. We are using the plurilocular sporangium of 
the brown Algae simply as an illustrative type of a reproduc- 
tive organ. To relate such an organ to the archegonium and 
antheridium we shall probably have to assume the existence 
of groups of green Algae with plurilocular sporangia of which 
no trace is left among living forms. This point will be 
considered later. 
However, it is well to point out that a few Chlorophyceae 
have structures identical with the very simplest types of 
plurilocular sporangia, although with nothing approaching 
the complexities of the higher conditions. In Schizomeris 
Leibleinii portions of a filament, at times terminal, may 
become transformed into a thickened region several cells in 
diameter, all of which develop zoospores. And again, in 
Draparnaldia and some related forms the reproductive cells 
of lateral branches sometimes divide longitudinally to produce 
a branch which departs from the structure of a single row of 
