develop and set free two or four new plants, in size and form
Ike the mother cell, except in the cytioderm or membrane ■
tins IS not granular, but smooth, and so remains until after the
multiplication by division takes place. After the first division
the new semi-oells assume the characteristic granular surface ;
le result of this first division is two plants, each composed of
one granulated and one smooth semi-cell. The second division
will make two perfect cells, and two which retain the one
smooth semi-cell. The third division produces eight cells, all of
form ’’ original two semi-cells, will be of typical
Although it has been stated in vague general terms that
zoospores are produced iu the Desmids, the only foundation for
the assertion appears to have been the presence of these bodies
in genera now excluded from the Desmidiaceæ. An examina-
lonof all these general affirmations precedes the announcement
y r. . Archer of his discovery of undoubted zoospores in
on. .p ,c ..s of Alllongh ,,p p „ „ V
h .„ r “ »f ‘I“ «onfiimolion of tl,. ,b ,
In order that these observations may be accurately stated, it
may be as well to quote them in the words of our author I t
may be premised that the Docidium in question was Docidium
Ehrenbergn. ‘ These bodies,” writes Mr. Archer, « although I
am quite ignorant of their after-development, I cannot but
beheve to be zoospores; and I imagine I am justified in the
conclusion; their appearance and mode of formation seem to be
so comparable to the zoospores in Oladophora, where they undoubtedly,
as IS well known in this, as in various other Algæ
propagate the plant and form young colonies in abundance, fh é
first indication of the commencement of the phenomenon is the pro-
ductionofa single minute hyaline lateral tubercle, or sometimes
0 two or, more rarely still, of three such tubercles, ju st under
This ttu^bbe rcl1 e a ris e s -a n d the ^same holds when there are two or
vHiiisi.t o(r1y860), pp. 215. quarterly Jouru. Micro. Science,” Vol.
three—not from any part of the original segments, but from a
special extension of the boundary wall interposed between the
inflated base of the segment and the sutural lino. In other
words, the tubercle is not produced between the segments by
their separation at the suture, but from an extension, or addition,
at the base to one only of the segments. When the
segment gives rise to one tubercle only, this additional growth
is gradually developed more and more narrowly, diminishing to
nothing at the opposite point of the cylindrical segment, so that
the frond is thus thrown out of the straight, or nearly straight
direction, and becomes bent into a knee-shape. Such is also
the case when two projections arise side by side. But when
two originate opposite to each other, or when there are thiee,
the frond is not thrown out of its straight form, because the
new addition to the segment, from which these lateral growths
take their origin, now forms an annular extension equal all
r o u n d , a n d the segment, therefore, becomes added to in length
by ju st so much as the annular addition is broad—and this is
less than -00033 inch (-0083 mm.)—but of very varied degrees
of length. I have noticed some to cease to grow after having
barelyMtained about one-tenth, or one-eighth part of the length
of the frond, and I have seen a few very long, almost, if not
quite as long, as the frond itself. The endochrome near the
base of each segment, and in the neighbourhood of the lateral
tube, next becomes very finely granular, of an almost homogeneous
appearance, and the lateral tube is filled by it. The remainder
of the endoohrome is still but little altered from the
ordinary condition, and the terminal cavities with the active
granules remain unchanged. The annular addition and the
lateral tubes are quite smooth, and destitute of the scattered
puncta which characterize the empty frond in this species.”
I have before stated that the endoohrome near the base of
each segment, and filling the lateral tubes, becomes very finely
granular ; it next becomes segmented into a definite number of
rounded portions, or “ gonidia.” I was never able to count
them exactly, but I suppose they were not less than twenty,
nor over fifty ; nor did the fact of there being either two or
three lateral tubes developed seem to indicate any very great
addition to the number of these bodies. That portion of the