172 PROCEEDINGS OF SOCIETIES, 
first sight, under alow power, this might possibly call to mind 
certain examples of that irregularly figured plant Polyedrium 
lobulatum (Nig.), or (less likely) that seemingly more rare plant 
Sorastrum spinulosum (Nag.) ; but a moment’s inspection under a 
higher power reveals that it is something altogether different 
from both. A goodly number of examples being present of this 
new form, both the mature and empty cells and of partially formed 
zygospores, all doubt was speedily set aside as to this little 
Cosmarium being a new and distinct species, not perhaps after all 
more marked by its peculiar zygospore, than, simple as it is, by 
the mature form itself, when carefully studied and contrasted with 
its allies. 
Dr. Moore exhibited Closteriwm Pritchardianum (Arch.) from 
the tank in the warm house watered from the ‘“ Tolka,’’ in the 
Botanic garden. It had since become conjugated, maintaining all 
the characters originally described for it. It had produced a 
stratum over the leaves of Owvirandra fenestralis detrimental to 
the latter. Indeed, Dr. Moore stated that unfortunately this 
plant was very prone to become choked up more or less by various 
growths ; last year an (Edogonium had seated itself upon it, much 
_ to its injury. 
Rey. E. O’Meara exhibited and described a number of new 
species of Diatomaceze which he had discovered in the rich 
gathering made by Dr. E. Perceval Wright off the Arran Islands. 
These he named Wavicula Hibernica, N. pellucida, N. denticulata, 
N. Wrightii, N. Amphiodes, Pinnularia Arraniensis, P. constricta, 
P. forficula. Descriptions of these, with figures, will appear in 
the ‘ Quart. Journ. Mic. Science.’ (See p. 113.) 
Mr. Archer exhibited, new to Britain, Hormospora transversalis 
(Bréb.), which he had taken at Kilbride, county of Wicklow. This 
exceedingly elegant little filament seemed, with us at least, to be 
very rare; he had never before encountered it, and in the present 
gathering it was extremely sparing. With a reference to de 
Brébisson’s paper and figure (‘ Annales des Sciences Naturelles,’ 
3 ser., tome 1. Bot., p. 25, t. i, fig. 2) it would be here unnecessary 
to describe the plant. But Mr. Archer thought it might perhaps 
be worth while to draw more particular attention to the fact of 
the self-division of the individual elongate cells taking place in 
the longitudinal direction, than de Brébisson seems to do. It 
seems a singular occurrence amongst these simple cellular struc- 
tures, the self-division taking place in elongate cells otherwise 
than transversely, that is, through the shorter diameter. Here 
the sharp line formed by separation of the parent cell-wall by a 
suture could be seen, and the opposite apices of the cells thus 
oftentimes presented an acute angle, formed by the extremities of 
the sharply-defined margins of the parent cell-wall,—adding to the 
beauty of the plant. 
