322 
a valvular structure, raised and lowered by the motions of the 
animal in and out of its case, just as in the cylindrical form called 
Vaginicola valvata. 
A vote of thanks was passed to Mr. Reeves for the opportunity 
to see this new and beautiful specimen. 
18^A March , 1869. 
Mr. Archer showed a new and minute freshwater Rhizopod 
referable to Dujardin’s genus Gromia. This rather inert-looking 
form at first called to mind somewhat the appearance of a Chy- 
tridium, but their occurrence not attached to any foreign body 
and a further observation showed their true nature. The test is 
very minute, orbicular, hyaline, smooth; body within the test 
opaque, bluish, granular, with an eccentric whitish nucleus, 
each with a central dark nucleolus ; pseudopodia often long, 
slender, hyaline, bearing in a slow circulation several darkish 
granules, often cohering by the pseudopodia one to the other in 
small groups. Mr. Archer hoped to shortly give a figure of this 
curious little form, with a description, and would meantime call 
this form Gromia socialis. 
Dr. E. Perceval Wright exhibited a section of a series of 
spicules belonging to a Creeping Sponge, met with by him at 
Make, which had been described by Dr. J. E. Gray as Placo- 
spongia melohesioides. He thought that though this genus was 
certainly closely allied to Geodia, yet that perhaps, until we knew 
more of the generic peculiarities of the Corticata, the genus 
may be retained. He brought it forward now chiefly in continua- 
tion of a series of notes already before the club on the “ Sponges 
of the Corticate Division” of Oscar Schmidt. Dr. Bowerbauk 
thinks that this species is the same as bis Geodia carinata 
(‘ British Sponges,’ vol. i, p. 239), but this does not appear to 
be the case. Duchassaing and Michelotti have described a genus 
called Acamas ; one species ( A . violacea) appeared to come very 
closely indeed to Placospongia melohesioides. 
Dr. John Barker showed a new Compressorium constructed by 
Mr. Ross, having the advantage of readily exerting a direct 
vertical pressure on the object, the extent of which is regulated 
by turning a screw placed at the left hand of the platform, which 
was made to receive an ordinary slide and cover, thus presenting 
the very valuable facility of being able to submit any object 
casually encountered without any difficulty to the action of the 
compressor. Dr. Barker, however, was about to suggest to Mr. 
Ross some modifications which would still further facilitate the 
use of this little instrument, so as to retain the slide at the most 
convenient place before the screw pressure became exerted. 
Dr. Moore showed the Spores of ILypnum stramineum in various 
stages of germination. In those farthest advanced the confervoid- 
like threads, as they issued from the spore, spread themseves over 
the surface of the leaf itself, which, being transparent, afforded a 
