1922] DUPLER—REBOULIA 145 
Usually there are four archegonia on each receptacle, one close 
behind the apical cell of each of the four growing points of the recep- 
tacle. Rarely three, occasionally five or six such growing points 
and archegonia may occur. In the typical condition the archegonia 
are so situated on the receptacle that a median section through the 
entire archegonium can be secured only by vertical sections cut on a 
plane at an angle of 45° to the long axis of the thallus (fig. 2). Owing 
to their curvature, both the archegonium and the early embryo are 
bilateral and not radial, and a strictly median section can pass 
through but one plane. With but few exceptions all the embryos 
figured in this account are from sections along this plane. 
The egg at maturity is about twice as long as its transverse diam- 
eter, bluntly rounded at both ends, slightly more tapering at the 
hypobasal end, and with its long axis describing the arc of a circle 
- (fig. 3). The nucleus is centrally placed, the egg cytoplasm uni- 
formly distributed, and containing plastids and oil globules. There 
is usually a very conspicuous oil globule near the anterior end, which 
persists even in late stages of the embryo. 
Fertilization 
The close proximity of the male and female receptacles on the 
same branch of the thallus usually insures fertilization, although 
occasionally it fails to occur. Woopsurn calls attention to the 
change which the motile sperm undergoes from the time it leaves 
the antheridium until its nucleus is ready to fuse with the egg 
nucleus. The writer found a number of cases in which the sperm 
nucleus had penetrated the egg cytoplasm and lay close to the egg 
nucleus (fig. 4). At this time the egg nucleus has about twice the 
diameter of the sperm nucleus, whose more compacted chromatin 
results in a denser staining body. No attempt was made to study 
the nuclear changes involved in fertilization. Apparently the fusion 
nucleus passes into the resting stage before division of the egg takes 
place. 
Embryo 
First DIVIsIon.—Without any considerable enlargement after 
fertilization, the egg divides by a transverse wall, usually per- 
pendicular to the long axis, and giving nearly equal epibasal and 
