48 THE WORLD OF THE SEA. 
According to the beautiful researches of M. Thuret, the following 
phenomena take place in the reproduction of the Fucus vesiculosus. 
The spore-cases take their origin from the cellules of the conceptu- 
lary cavity. Some of these cellules rise above the others, forming 
a little projection, which is cut in two by a transversal partition. 
The lower division ceases to grow, and forms from that time 
the pedicle ; the upper one continues to increase, is gradually filled 
with olive-green matter, and becomes a spore-case. In due time 
this matter divides itself into eight parts, which become so many 
spores. In this, their united state, they form an octospore. This body 
appears as an opaque or brown mass, enclosed by two transparent 
membranes. The exterior membrane (ferzspore) belongs to the 
spore-case, and remains united to the pedicle when the latter has 
burst. The interior membrane (efzspore) adheres to the enclosed 
mass, and holds the spores tightly together. At their birth the octo- 
spores slip out of the orifice of the conceptacle, and disperse them- 
selves through the water. Soon they increase in volume, and in 
time the enveloping membrane (epispore) begins to give way at the 
upper part, and then it is seen (fig. 1, Plate II.) that the spores are 
still held together by a third very fine membrane. The lower part 
of the epispore, which is not broken up, is folded back upon itself, 
to allow the spores (fig. 2) to issue out; it separates completely, 
only holding by the base of the interior membrane (fig. 3) ; finally 
this third membrane breaks, and the spores escape (fig. 4). All 
this takes place in less than an hour. The liberated spores are 
perfectly round, of a yellowish olive-green tint, utterly destitute of 
teguments. This is the moment that the action of the anthero- 
zoids interferes to impregnate the spores now disengaged from 
their envelope. It is only necessary that some antherides should 
be in the water which contains these reproductive bodies. Under 
the influence of moisture the antherozoids become liberated from 
their antherides (fig. a), surround the spore, and attach themselves 
to its surface (fig. 5), and, by means of their vibratile cilia they 
communicate to them a very rapid revolving motion. This move- 
ment gradually becomes slower, and in about half an hour ceases 
altogether. In some hours the spore becomes covered with a 
membrane, and in a still longer time a partition appears, which 
divides it into two cellules (fig. 6). At the same time (fig. 7) a 
