ORIGINAL COMMUNICATIONS. 
Note on ‘ ASTERIDIA” occurring in PENIUM DIGITUS 
(Bréb.). By Wittiam ARCHER. 
Some time ago I made a gathering of some minute alge 
from a pool near Enniskerry, on the road going towards 
Lough Bray. Amongst these a number of globular, densely 
spined bodies, with green contents, conspicuously presented 
themselves. The spines densely covering these were very 
numerous, very slender throughout, and acute. The bodies 
themselves were mostly to be found distributed in pairs 
over the field of view. These might easily be taken for so 
many zygospores of some desmidian ; but much as such a 
structure resembled a possible zygospore, these bodies were 
not like that known of any species of the family Desmidiee, 
nor was there any evidence in the gathering that they might 
actually be zygospores of any form not yet known in the 
conjugated state. 
Hence, but for an observation made by me on a previous 
occasion, the source of these curious bodies would have been 
not a little puzzling. 
In a gathering which I had made in the previous year, 
not, however, from the same locality, I took a quantity of 
the common desmidian, Penium digitus (Bréb.), and a con- 
siderable number of them showed, some individuals one, the 
majority two, and a few three, quite identical stellate bodies 
in the interior of each cell; these seemed to me evidently 
to have been formed at the expense of the individual Penium 
in which they occurred. Some of the Penia showed their 
cell-contents partially absorbed, and the remainder dead and 
brown, whilst others did not exhibit a trace of the original 
contents, but contained the (generally) two spinous bodies, 
green and vigorous, one in each half of the old cell-cavity 
of the Penium, the outer wail of which still enveloped them. 
But afterwards these bodies might be found abundantly 
without the encompassing old membrane of the Penium, and 
usually distributed in pairs over the field. (Pl. VIII, fig. 4.) 
VOL. VII.—NEW SER. N 
