Microscopical Society. 347 
circumstances prevented their chemical examination, and conse- 
quently they could only be operated upon mechanically. Their shape 
is that of a flattened sphere, the major part of them closely resem- 
bling some of the gemmules of sponges, most of them having a cir- 
cular opening. The arms of all appear to be closed at the ends and 
not tubular, as has been supposed, from the examination of some of 
the flint specimens under pressure in water between two pieces of 
glass: they were torn asunder in the same manner as a horny or 
cartilaginous substance would be, and the arms in contact with the 
glass were bent; some, after maceration in water for several weeks, 
became quite flaccid, thus entirely disproving their siliceous nature. 
On the contrary, there is every reason to suppose them to have been 
of a horny or cartilaginous nature. Some other bodies resembling 
the husks of peas were also observed, which appear to be identical 
with the Pividicule in flints ; but these, although agreeing in colour, 
he does not consider to have any relation to the Xanthidia, but, from 
their close resemblance to sponge-gemmules, to be some animal or 
animals in a progressive state of development. 
Another paper by the same gentleman, ‘‘ On a mode of isolating 
the siliceous shells of Infusorial animals found in the Ichaboe 
Guano,” was also read. After premising that the guano from Ichaboe 
was soon found to contain siliceous shells of microscopic animals, 
allied to those brought from Richmond in Virginia, and from Ber- 
muda, he stated that the extreme difficulty of finding them in the 
ordinary mode induced him to try whether, by decomposing the 
guano by means of nitric acid, more satisfactory results might not 
be obtained. The experiment was successful, and the following is 
the method he employed. Take any quantity of pure Ichaboe guano, 
and wash it by repeated ablutions of distilled water until the water 
is no longer coloured, observing after each addition of water that it 
must be well-stirred two or three times and allowed to settle for 
some hours. When sufficiently washed, a small quantity of hy- 
drochloric acid is to be added to the water last used. This dis- 
solves some portion of the guano with effervescence, and causes a 
more perfect subsidence of that portion which it does not act upon. 
After this, allow sufficient time for the deposit to become well-settled 
down ; then the clear liquor being poured off as closely as possible 
without loss of the sediment, a quantity of strong nitric acid in the 
proportion of two acid ounces to every ounce by weight of the guano 
employed is to be added; a strong effervescence results, which is to 
be assisted by its being placed in a warm situation at a temperature 
of about 200° for six hours, during which time the greater part of 
the guano will be dissolved. After allowing it to stand in a cool 
place for twenty-four hours, pour off the acid liquor and wash the 
sediment with plenty of distilled water. The fine portion of this 
sediment will contain all the siliceous shells of the guano, perfectly 
freed from extraneous matter. 
