PROCEEDINGS OF SOCIETIES. 17] 
was a thing distinct, a good and true species of Cosmarium, but 
hesitated to describe it, inasmuch as this—a mere very minute 
elliptic cell—would doubtless with difficulty be received as a species 
distinct from every other little elliptic cell; he felt that it might 
be hard to convey to others, either by description or a figure, the 
characteristics of this little humble production as these presented 
themselves to himself, sufficiently evident as he might think 
them. Hence he was now the more pleased to find this plant 
conjugated, and to perceive that its zygospore could never be 
mistaken, in its outer characters, quite irrespective of its dimen- 
sions, for that described for any other species. 
The following may serve as a description: 
Cosmarium (Corda). 
Cosmarium lobatosporum, sp. nov. 
Frond very minute; nearly twice as long as broad; general 
form elliptic ; ends rounded; constriction an extremely shallow 
and very gentle narrowing. Zygospore rounded, somewhat 
irregularly lobed ; the lobes surmounted by one or two minute 
pellucid conical and pointed spines or mucrones ; cell-wall reddish. 
Length of cell =1,,", breadth +55", diameter of zygospore about 
idoo » Including spines. 
Devoid, however, as this little form, in the unconjugated state, 
may be of any very striking or tangible characters for descriptive 
purposes, yet Mr. Archer thought he might venture on saying 
that it would appear to him a mere waste of words to contrast it 
with any other minute elongate cell not desmidian. Amongst 
Desmidiew, Mr. Archer thought that perhaps the form most likely 
to be confounded with this might be Peniwm Mooreanum (ejus). 
(See ‘ Quart. Journ. Mic. Soc.,’ n. s., Vol. IV, p. 179, Pl. VI, figs. 
34 to 44), and he exhibited the figures in illustration. But the 
latter is notably broader in proportion to its length, and is larger, 
and quite without any narrowing at the middle; in fact, it is 
barrel-shaped, except as to the ends being however rounded (not 
truncate). Further, the arrangement of the endochrome is quite 
different; in Peniwm Mooreanum the chlorophyll is in longitudinal 
*‘ fillets,” that is, deposited in longitudinal plates, radiating from 
the axis of the cell; in the present plant it is scattered with a 
central granule in each segment. In a word, they belong to two 
seemingly well-marked genera. But even regarded specifically, 
besides what has been alluded to, see the remarkable differences 
in the zygospore of each. It seems not at all necessary to con- 
- trast this new form with any others at all approaching, such as 
Cosmarium Cucurbita, well distinguished by its considerably 
greater size and its punctate cell-wall and groove-like constric- 
tion, or with any species of Mesotenium or Cylindrocystis. But 
above and beyond what has been mentioned, this new form differs 
from every other desmidian whose conjugated state is known, by 
the remarkable more or less lobed character of the zygospore, the 
lobes or projections surmounted by the short conical spines. At 
