Fertilization in Laminaria and Chorda . 605 
growths are very irregular in form and always creep along the bottom. 
The male gametophyte behaves very differently. It is much smaller than 
the female : it divides up into much smaller cells, which are more numerous 
than in the female gametophyte. Sometimes all the cells are short, and 
the plant is compact ; in others the branches are thin and slightly elongated. 
Any cell can function as an antheridium. The process commences in the 
end cells, which become much paler ; the wall at the apex of the cell 
swells greatly and forms a cap or beak ; this eventually bursts, and the 
single antherozoid swims away ; ultimately all the cells of the gametophyte 
become emptied of their contents. One of the first signs of the approaching 
maturity of a culture is the appearance in it of a few empty terminal cells 
with openings at their distal ends. Soon after this, the oogonia begin to 
be differentiated. The one-celled gametophytes, or one or more cells in 
a multicellular gametophyte, elongate slightly, and become pear-shaped. 
The w r all covering the narrow end becomes very greatly thickened and 
differentiated into three layers, the middle one showing a laminated 
structure. The chromoplasts in the narrow end are crowded together, with 
their long axes parallel to that of the oogonium, and there are evidences 
of strong internal pressure. A narrow fissure appears in the innermost 
layer at the apex' of the oogonium ; this extends outward, but very often 
before its completion the outer layer bursts and gapes open ; the contents 
are then pressed out through the opening, now much widened. When the 
whole protoplast has emerged, the thick walls close elastically, and the 
only evidences of the aperture are a very faint median line and a rim or 
collar embracing the base of the protoplast, which thus appears seated in 
a very shallow cup. 
One remained long without any clear evidence as to the particular 
stage at which fertilization was effected : though not probable, it was 
possible that the antherozoid effected an entrance into the oogonium 
through the swollen, mucilaginous apex, and that this may have formed 
the impulse bringing about the liberation of the egg. Now, however, one 
is able to decide the question, for the eggs have been seen emerging, and, 
in the cases where antheridia matured at the same time, they have been 
seen surrounded by active antherozoids. Thus, there can now be no doubt 
that there is here a differentiated oogonium, and that the single egg 
produced by it is fertilized after emergence. Fixed and stained prepara- 
tions often show the gametic nuclei in various stages of fusion. These 
nuclei cannot be the result of the first division of the oospore nucleus, for, 
as will be explained later, the appearances presented at that stage are 
totally different. In one instance the egg had not completely emerged ; 
and its nucleus, elongated and somewhat deformed by pressure, was 
actually in the narrow neck of the oogonium while the male nucleus had 
already entered the free apex of the egg. 
