]\I. Deeaisne, and Mr. Jenner regard as the true spores, Mit
Avhich, Agardh declares, resolve themselves after a time into
zoospores, an opinion in which I concur, applying the term
sporangia to them.
The tubes of communication do not appear to issue from
any determinate point of each cell, but from that which lies
in nearest contact with a neighbouring filament ; the filaments
appearing to exercise a mutual attraction on each other : thus
a number will be given off in succession to corresponding
ones of a filament near to it on one side, while another set from
the same filament Avill unite with those of another coming
near to it in some other part of its length.
I t is curious to remark that the cells in one part of the
same filament will part jvith their contents and remain
empty, Avhile in another, they will be the recipients of the
contents of the cells of another filament.
This remarkable mode of union of the filaments, almost
without parallel In the vegetable kingdom, jvas first noticed
by ISIidler in a species Avhlch he named Conferva jugalis.
hliiller, however, did not entertain the slightest suspicion that
it was in any Avay connected with reproduction.
Since the time of the publication of Vaucher’s “ Histoire
des Conferves d’Eau douce,” in 1803, but little seems to have
been added to the information contained In tha t excellent
work in reference to this division of the Algæ, in which the
phenomenon of union of the cells is shewn to belong to very
many species, Avhich Vaucher for the most part has satisfactorily
determined, notAvithstanding the feeble power of the
instrument employed by him in their investigation. The
labours, however, Avhlch I have bestoAved upon the freshAvater
Algæ have been rewarded Avith a few discoveries of
interest, one of Avhich I shall now proceed to notice.
This relates to the fact, tha t certain species of Conjugateoe,
belonging principally to the genus Zygnema, occur, in wliich
there is no union of the different filaments similar to that already
described ; the sporangia being formed in these by the
concentration of the matter of tAvo cells in the same, and not
as in the ¡^receding case in different, filaments. This interesting
fact Avas first announced by me in a paper on the Zygneinserted
in the 9th vol. of the “ Annals and Magazine of
Natural History,” p. 34. Sinccthis paper was published I have
observed, in DilKvyn’s “ Synopsis of the British Freshwater
Algæ,” that a non-conjugating Zygnema has been described
accurately by Mr. Woods, under the idea of its being a variety
of Zygnema quininum. The accuracy of the description Avould
appear, hoAvever, to have been doubted, since we find no reference
to the species, Avhlch is distinct, and not a variety of that
to which it Avas referred, made by subsequent Avriters on the
Algæ. Mr. Harvey in his excellent “ M anual” does not make
any mention of it.
^ In these non-conjugating Zygnemata the tubes of communication
issue from the opposed extremities of the cells, and
not from the centre of the sides of the cells, as in the conjugating
Zygnemata.
T h e analogy which exists betAveen th e conjunction of the
filaments of th e Conjugateoe and th e reproduction of animals
has led to th e opinion being entertained by some th a t th ey
a re animal and no t vegetable productions. The erroneous
n a tu re , however, o f this vicAv is easily proved by reference to
th e non-conjugating species mentioned, these testifying th a t
th e conjunction of the filaments is no t an occurrence essential
to th e p e rp e tu ity of th e species, and th a t therefore no a rg u ments
in favour of the animality of th e Conjugateoe oug h t to
be founded on th a t circumstance. The union, however,
o f distinct cells in th e same filament might be regarded
as indicative of an animal n a tu re ; b u t this vicAv may be disproved
by reference to another genus o f freshAvater Algæ, of
th e vegetahility of Avhich th e re can be no question, viz. Ve.si-
culifera, in Avhich th ere is an union o f the m a tte r of two cells
in th e same filament, though no tu b u la r connection between
those cells. Now th e analogy betAveen the species of this
genus and th e non-conjugating Zygnemata is too g re a t to
permit o f th e opinion being entertained, th a t th e former are '
vegetables and the la tte r animals.
Some have accounted for th e union of the filaments by
supposing th a t th e en tire of one filament contained fertilizing
and th e other fertillzable material ; b u t th is vicAV is lik e Avise
shoAvn to be erroneous by the occurrence of non-con-
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