182 THE MICROSCOPE. Dec. 



cap (C) with its centrally perforated mica cover (m m) in 

 place and slip it down over the drum (D) so as to hold f 

 down upon P. Then with a fine nozzled pipette moisten 

 the central exposed part of f, and with a pair of fine for- 

 ceps pick up one of the little disks of elder pith and lay 

 it, convex side down, upon the center of f, when it will 

 immediately flatten out and adhere to f, nearl}^ covering 

 the central area not covered with paraffine. 



On placing a drop of water (d) swarming with animal- 

 cules on E, it will be found that the water will be rapidly 

 drawn through e and f into P, in the direction indicated 

 by the arrows. In this way several drops of water may 

 have much of their animalcular population separated out 

 and caught upon the surface of E. To kill the contents of 

 D add a little saturated corrosive solution or osmic acid 

 one per cent, by simply thrusting the charged end of a 

 wooden rod (t) into the drop (d). The animalcules are at 

 once precipitated upon the upper surface of E, where they 

 are caught and held in the meshes of the pith cells. Re- 

 move the filter e by raising its free edge slightly with a 

 needle, then grasp this edge with a pair of sharp pointed 

 forceps and transfer to a watch glass containing 50 to 60 

 per cent alcohol. With gentle handling Ciliates may be 

 passed through several reagents without becoming de- 

 tached. 



Even orientation may be very easily effected, either by 

 sketching with a low power the outline of the whole disk 

 and the position and direction of the axes of the very 

 minute objects upon it, or by shaving down the block 

 after the disk of pith is embedded so as to make it suffi- 

 ciently transparent to show the shape of the adherent or- 

 ganisms through the semi-transparent block. The proper 

 cutting planes may now be indicated on the margin with 

 lithographic ink. 



I have found it very easy to thus capture, hold, kill, 

 dehydrate, stain, embed and cut Paramoecium aurelia. 



