DUBLIN UNIVEESITY ZOOLOGICAL AND BOTANICAL ASSOCIATION. 261 
wall. We have seen that there is not an interruption of the endochrome 
until the commencement of the process of division. As to the mode of cell- 
increase which prevails amongst the Desmidiaceee, it does appear probable 
that during the division and formation of the constriction, the original 
hemispheres may be pushed asunder, by new growth, without their mate¬ 
rially altering. But, even so, is this an exclusively Desmidian (and Diato- 
macean) characteristic ? An apparently similar mode of division seems 
to hold good with the greatly more minute cells of the moniliform fila¬ 
ments of the hTostochaceous Algse (e. g. Dolichospermum). One of these 
globular cells appears to elongate, to become constricted into a figure of 8 
form, deeper and deeper, until two new globular cells grow out of one, 
during which process the opposite hemispheres of the original cell appear 
to remain unchanged. So in the plant in question. The main distinction 
appears to be, as I apprehend, that in neither of these organisms is the 
first step of the process of division—the formation of a septum between 
the halves of the cell-contents, as appears to prevail in the Desmidiacese. 
So far as I can make out, the halves of the contents of the cell about to 
divide (in the plants alluded to) merely become retracted from each 
other, separated by a sharp, smooth line of demarcation, and eventually 
become shut off by an addition to, and external gradual constriction of, 
the original outer cell-wall, as well as, of course, the original pri¬ 
mordial utricle, afterwards producing each its own proper cell-membrane. 
In other words, the new and intervening growth appears to be an ex¬ 
tension and continuation of the original outer wall of the dividing cell, 
—still a single cavity only, until the constriction becomes shut off, or 
until the halves of the cell-contents have withdrawn and become invested 
each by its own special coat,—not, as in Desmidiacese, according to 
Hofmeister, the expansion of the “younger inner layer of membrane not 
firmly adherent to the older portions.” But, again, both our Dublin plant 
and Hofmeister’s appear to have some affinity to Glaeocapsa. In them, 
however, there is enclosed, in the loose outer cell-membrane, only one 
green cell,—-not as in Glaeocapsa, 2, 4, 8, &c. But there does appear, 
perhaps, a greater similarity in the separate persistence for some time of 
the outer cell-wall in each. In Glaeocapsa the outer concentric layers, 
formed by their solution into a confluent gelatinous mass, usually remain 
in some numbers—in M. Hofmeister’s plant he states to the number of 
six sometimes—the chief difference in this respect apparently being, that 
they do not, as in Glaeocapsa, become gelatinous, but are eventually cast 
off as loose wrinkled membranes. The green cells sometimes escape from 
Glaeocapsa, too, by a fracture at the side, leaving behind the empty con¬ 
centric layers. 
It is greatly to be hoped that upon a study of his plant M. Hofmeister 
may decide upon “ a local habitation and a name” for it (and along with 
which, I apprehend, our plant must follow), which, simple in form as it 
may be, appears a sufficiently puzzling problem. I have, nevertheless, 
thought it possible that this imperfect notice of the occurrence with us 
of an organism, at all events closely allied to, if not identical with, that 
VOL. V.-PEOC. SOC. 2 M 
