Microscopical Society. 847 



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 Pixidiculce in flints ; but these, although agreeing in colour, 

 he does not consider to have any relation to the XantJiidia, 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 sufliciently 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 eff^ervescence, and causes a 

 more perfect subsidence of that portion which it does not act upon. 

 After this, allow sufl&cient time for the deposit to become well-settled 

 down ; then the clear liquor being poured oflf 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 eff'ervescence 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. 



