Ralfs British Desmidieae. 1243 



these bodies in various ways for examination, suggested to him the possibility of ascer- 

 taining their true nature. Their minuteness, and other obvious circumstances pre- 

 vented their chemical examination, and consequently they could only be operated upon 

 mechanically. Their shape is that of a flattened sphere, the major part of them closely 

 resembling some of the gemmules of sponges, most of them having a circular opening. 

 The aims 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 cartila- 

 ginous 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 disprov- 

 ing their silicious 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 pixidiculse 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 silicious shells 

 of Infusorial Animals found in the Ichaboe guano,' was also read. After premising 

 that the guano from Ichaboe was soon found to contain silicious shells of microscopic 

 animals allied to those brought from Richmond in Virginia and from Bermuda, 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 Hydrochloric 

 acid is to be added to the water last used ; this dissolves 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 nitric acid, in the proportion of two fluid ounces to every ounce 

 by weight of the guano employed is to be added ; a strong effervescence takes place, 

 which is to be assisted by its being placed in a warm place, at a temperature of about 

 200 for six hours, during which time the greater portion 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 silicious shells of the guano perfectly free from extra- 

 neous matter. — /. W. 



New work on the British Desmidiece. — Our readers will be pleased to learn that 

 Mr. Ralfs of Penzance, is about to publish a monograph of this interesting tribe of 

 microscopic beings. The author proposes to describe all the British Desmidieae, and 

 as correct figures will be absolutely essential to make the descriptions of such minute 

 objects intelligible, he will spare neither care nor expense in rendering the plates, 

 which will be executed under his own eye, as accurate as possible. The engravings 

 will be on copper, since experience has proved, that the delicate markings of the Des- 



