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Mr. Stokes exhibited and described a simple apparatus for aerating living 

 fish whilst under microscopical observation. 



This apparatus is shown in perspective view at Fig. 2, Fig. 3 being a 

 longitudinal section. In these figures a, a, are two wedge-shaped slips of 

 wood, well soaked in paraffine wax to render them waterproof, b, b, are 

 two 3X1 glass slips, which are so arranged as to form, with the wood slips 

 a wedge-shaped glass box. 



The larger end of this box is enclosed in a short piece of indiarubber 

 tube, c, and this tube is closed by a cork. 



A short piece of glass, d, is fixed inside about midway between the glass 

 sides of the box, so that it will form a shelf upon which the fishes tail 

 may lie during examination, as shewn in fig. 3. 



At either end of the box are fitted two short glass tubes, 6", e, which when 

 the instrument is in use are respectively connected by indiarubber pipes 

 with two bottles. One of these bottles is to be placed on the table below 

 the level of the microscope stage, and the other — filled with water — a little 

 above the level of the stage. The water will then trickle down from 

 the upper bottle, through the wedge-shaped box into the lower bottle, and 

 when the latter is full the position of the bottles may be reversed, and 

 in this way a constant circulation kept up for any length of time. 



Dr. Matthews said that some few years ago he exhibited a live slide on 

 the same principle as that shown by Mr. Stokes. It was not his own idea, 

 but was an article imported from America by Mr. Beck. It consisted of a 

 thick piece of glass excavated in some way, and had a piece of small pipe 

 inserted in each end ; it was perfectly true on its surfaces, and when used 

 it was only necessary to cover it over with a thin piece of plate glass. It 

 answered the purpose admirably, so that he was able to use the same fish 

 eight or nine times. 



