reproductive body, the cells are absorbed, at least the spores
issue by a rounded aperture which they constantly present at
this period. These corpuscles have offered me in this case an
ovoid form, and I have seen them without exception issue
forth, presenting in advance their colourless extremity. ”
Of the many hundreds of specimens of Conjugata which I
haA'e examined, it has never occurred to me to observe the
slightest change in the primary form of the spores or sporangia;
lohat they really are seems to me a point yet to be
determined, nor have I ever seen the colourless extremity
referred to.
The opinion of the production of the same species from two
organs so dissimilar in size and form as the zoospores and
spores are, is not so startling when the structure of these
is closely considered, as at first sight it might appear. The
zoospores being regarded as young cells of Conferva, containing
only one or two other incipient germs or zoospores,
and the spores as cells of larger growth, filled wdth
germs, or zoospores, which ha\’e arrived at or near their
maturity.
The organ contained within each capsule of the different
species of the genus Vaucheria, I regard likewise as a sporangium
filled with zoospores, the horns near it being identical
in function with the vesicle already described. • The- ciliated
ovum formed at the extremity of the filaments of Vaucheria
is of course different from the capsular bodies. Having thus
given a general outline of the more interesting and leading
facts connected with the reproduction of the freshwater Alga,
we shall next proceed to the consideration of their structure
and modes of growth.
The structure of the Conferva is exceedingly simple. An
outer membrane, transparent as water, invests a number of
cells, which exhibit under the microscope not unfrequently
a fibrous appearance. These cells do not communicate with
each other, although their truncate extremities are always in
apposition the one with the other. They contain a thick and
generally colourless fluid, in which arc immersed, and sometimes
scattered irregularly, as in the true Conferva, sometimes
disposed in starlike forms, and sometimes in spires, a number
of vesicular bodies, the immature zoospor.es, and in these it is
that the colouring matter of the plant chiefly resides. I t is
from this viscid fluid, the quantity of which is so considerable,
that the Conferva derives its nourishment and means of
increase, and not, at least so I consider, from the Intercellular
substance of Mohl, to whose theory an objection occurs to my
mind, in the fact that it is not rational to suppose tha t the
nutritious fluid should be placed external to the cavities of
the cells, the contents of which it is destined to nourish.
Such is the view usually entertained, I believe, of the
general structure of the filamentous Alga. The opinion
at present held by Mr. Jenner as to their organization differs
considerably from that just stated, that gentleman declaring
that he has, in the Zygnemata, detected a third membrane of a
delicate and homogeneous appearance, and that it is by this that
the dissepiments are formed, and not by the second, which
terminates ju st at the situation of the joints, between which
it does not send down any partition walls. Thus the outer
membrane he describes as continuous, the second as a series
of short tubes, open at their extremities, placed end to end,
and the thh-d as the true cells. Of the accuracy of this
ingenious view of the structure of the filaments of the
Zygnemata, &c. I have not as yet been able to satisfy myself.
The investing membrane of the cells, one would suppose,
Avould be essential to the existence of a Conferva ; yet M.
Areschoug, in an excellent article on Hydrodictyonpentagonum,
states that th a t curious production does not possess it. In
the Ulvacea the cells are not usually placed in linear series,
b ut are scattered through a gelatinous substance, which is
usually furnished with an investing membrane.
As the different cells of a Conferva do not communicate
directly with each other, each cell may therefore be regarded
as possessing a separate and independent existence, inasmuch
as it contains all the parts requisite for the formation of an
entire Conferva. A Conferva then may be regarded, like the
associated Zoophyte, as a compound or aggregated being ; and
it is to this aggregation of similar parts th a t the Conferva owe