199 
haps the very commonest and most abundant of filamentous 
desmids ; whilst D. aptogonum, as mentioned, is. a rare form in 
either of its varieties. 
Ylth December , 18G8. 
Dr. John Barker exhibited a Chytridium, or some allied orga- 
nism, attacking a specimen of Closterium lunula, endogenous in 
habit, but perfecting its growth externally to the Closterium. 
Pending want of information as to the mode of exit of the zoo- 
spores, whether by one or several pores, and whether these are fur- 
nished or not with a lid, no very satisfactory opinion could be 
arrived at as to its exact location or identity. The present speci- 
mens, however, presented the character that the internal lower 
portion, from whence seemed to emanate root or mycelioid pro- 
cesses, was connected to the external and upper portion by a 
slender isthmus-like tubular junction, and through this, in the 
progress of development, passed up the granular contents from 
the lower cavity, leaving it seemingly empty, preparatory, evi- 
dently, to becoming changed into zoospores. It seemed, there- 
fore, that this might be identical with Chytridium laqenaria 
(Schenk). 
Mr. Archer brought forward a new Rhizopod, taken near 
Carrig mountain, which formed a second species in Carter’s genus, 
Acanthocystis. At a first glance this form might possibly be mis- 
taken for an ovum of some rotatorian, and he had for a little been 
in some doubt as to its true nature. However, even before the 
pseudopodia made themselves apparent, he had fully made up his 
mind that it was no doubt a congener of Carter’s fine and very 
marked species. Even without seeing the pseudopodia extended, 
the slender acute spine, which stood out from the periphery, being 
often pointed in various directions, and frequently deciduous, as 
well as the outer covering, presenting a number of those short 
• slender spicules, lying in the direction of a tangent, similar to 
those of A. tuifacea, at once decided that this was no rotatorian 
ovum. The body contained numerous minute, though variously 
sized, colourless granules ; the pseudopodia, which the creature 
is somewhat diffident in extending, are slender, but present a few 
minute granules moving up and down. This is a much smaller form 
than A. turfacea. It will be seen, then, that it is distinguished 
from that species by its smaller size and its short acute spines of 
equal length (not elongate, and in two sets of different lengths, 
and cleft at the apices), and by the seeming constant absence of 
chlorophyll-granules (whereas in A. turfacea these are nearly con- 
stantly present). There is by no means a want of resemblance to 
Perty’s form, called by him Actinophrys brevicirrhis (“ Zur Kennt- 
niss kleinster Lebensformen,” p. 159, t. viii, fig. 7) ; and there is, 
perhaps, just a possibility that it might really be that form, suppos- 
ing Perty to have overlooked the spines, taking them (in examples 
in which the pseudopodia themselves were not extended) for the 
