96 
and were those illustrative of his recent paper on this subject in the 
‘Annals of Natural History.’ 
Dr. Purser exhibited two microscopes—one by Nachet, the other 
by Hartnack—his principal object being to show the immersion 
lenses of those makers, which have gained so great a celebrity on the 
Continent. Dr. Purser claimed that they admit more light, have a 
greater working distance, and require much less pains in the illumina- 
tion, than non-immersion lenses of the same power.—Dr. Purser 
likewise exhibited a stage upon which objects could be kept at an 
elevated temperature whilst under examination. He further showed 
some preparations illustrative of the use of chloride of gold and 
nitrate of silver in histological research. 
Mr. Archer drew attention to the most abundant gathering of the 
unicellular alga, Polyedrium lobulatum (Nag.), he had met with, 
noteworthy, perhaps, as this not uncommon form generally occurs 
seemingly rather isolated. From another gathering he showed 
uncommonly large examples of a Polyedrium, more approaching the 
more rare Polyedrium tetraedricum (Nig.), but the angles more 
rounded, and without spines. It may remain a question if this be 
really a distinct thing. Only for its (comparatively) large size 
(about z4,”" in diam.) one might be inclined to regard this as 
Polyedrium muticum (Al. Braun), which, however, is recorded as 
only -; mm. in diam. (Al. Braun, in ‘Algarum unicell. Genera 
nova,’ &e., p. 94, in note). 
Dr. Moore showed the beautiful and curious aquatic moss Cono- 
mitrium Julianum in various stages of development, which made 
very interesting microscopical objects in a young state. When the 
calyptra almost envelopes the whole capsule the bright purple 
teeth of the peristome are seen through it to good effect, and when 
more advanced and the calyptra removed the pyriform capsule with 
pointed lid is also a pretty object. Dr. Moore mentioned that he 
was indebted to W. Wilson, Esq., of Warrington, the veteran mus- 
cologist, for the possession of this rare moss, which he was cultivat- 
ing successfully in one of the small conservatories in the Botanic 
Garden, in a jar filled with water. From his experience he believed 
it would be most valuable for cultivating in small fresh-water 
aquaria, in asimilar manner as Fontinalis antipyretica or Oinclidotus 
Sontinaloides are now grown, but much prettier than either. 
21st July, 1870. 
Mr. Crowe showed a Cosmarium from near Multyfarnham, which 
seems most likely to be new; it may be said to be medium-sized, 
its segments elliptic, longer than broad, rough with minute pearly 
granules ; end-view circular; constriction shallow, acute. This is 
rather a difficult form to decide upon; it resembles somewhat C. 
amenu. 
Mr. Archer mentioned he had taken this Cosmarium both at 
Multyfarnham and at Glengariff the previous spring, but had kept 
if in abeyance until he might become acquainted with C. amenum, 
and compare both with C. cylindricum. 
