central organ are really sometimes more than mere streams;
at least, that they are mucous threads, since they become
tinged brown with the tincture of iodine, and do not in the
least alter either their form or position. Schleiden has also,
at the same time, observed reticulate, anastamosing little
streams upon the central Avail of the cell, but especially at
the free ends where the green spiral bands cease, and the
cells consequently become lighter and more transparent.
This appearance, also, has not yet presented itself to me. I
have, hoAvever, more than ten years ago, seen in the Zygnemata,
motions of very little granules, Avhich resemble those
Avhich I have already pointed out in Oedogonium vesicatum
and O. capillare. They extend sometimes throughout the
entire inner space of the cell, and are especially evident in
freshly broken-off terminal cells. That the cytoblast really
occasions this motion, I doubt, because it occurs in all
the other cells of the Alga Avhich do not possess the central
oi'Ecans.”
Havino: thus described Avhat I conceive to be the organ
Avhereby the reproductive germs are fertilized, Ave come noAV
to consider these bodies themselves, which, according to
some observers, are tAVofold— zoospores and spores. W e shall
speak first of the former. When a portion o f a Conferva,
for example a Vesiculifera, in an early condition o f its growth
is placed beneath the microscope, in each cell are observed
numerous spherical granules, each having a dark central
nucleus, and the size and amount of these varying extremely
; and aU being, at this period, connected with each
other by a tubular or vascular netAVork.* As the species approaches
to a state of maturity, these bodies Avill be seen to
have undergone a considerable increase of size and change of
form, they noAV being no longer spherical, hut pyriform, the
inflated portions being filled with endochrome, in the midst of
Avhich one or tAVO incipient germs can, even at this early
period, he observed, and the apices, or, as they have been
* For an account of this, see paper hy me in “ Annals and Magazine
of Natural History,” vol. xii. p. 25.
termedi the rostra, being transparent; near which also is
sometimes observed a pinkish spot similar to that Avhich is seen
in the infusory animalcules. The vascrdar network has noAV
disappeared, and the zoospores lie detached in the cell. A t
length the granules become perfected, and they are noAv seen
moving restlessly about the interior of the cell, frequently
striking against its walls, as though anxious to escape from
the confinement of their narroAV cell, and to rove about, independent
beings, through the Avatei’s, in search of an appropriate
ahiding-place. Having escaped from the cells,
Avhich they are enabled to do, not as Agardh supposed, by
the multiplied knockings of their beaks against its sides,
whereby its fibres become displaced, but either by rupturing
its walls, through their increased developement, as in Ltjrig-
hya, &c., or by some special provision, as in Vesiculifera,
Zygnema, &c., they fall into the water, through AAdiich they
speedily begin to move hither and thither; now progressing
in a straight line, with the rostra in advance; noAV Avheeling
round and pursuing a different course; noAV letting their
rostra drop, and oscillating upon them, like (to compare
small things with great) balloons ere the strings are cut, or
like tops, the centripetal force being nearly expended; now
altogether stopping, and anon resuming their curious and
eccentric motions. Truly Avonderful is the velocity with
which these microscopic objects progress, their relative speed
far surpassing that o f the fleetest race-horse. After a time,
hoAvever, which frequently extends to some two or three
hours, the motion becomes much retarded, and at length,
after faint struggles, entirely ceases, and the zoospores then
lie as though dead: not so, nevertheless; they have merely lost
the power of locomotion; the vital principle is still active
within them, and they are seen to expand, to become partitioned,
and, if the species be o f an attached kind, each zoospore
wiU emit from its transparent extremity two or more
radicles, whereby it becomes finally and for ever fixed. Strange
transition, from the roving life of the animal to the fixed
existence of the p lan t! In exact correspondence with this,
is Avhat occurs Avith the Zoophytes.