380 ME. WALTEE WESCHE ON THE GENITALIA OF 



(10) A preparation is then lifted out witli a section-lifter and placed in tlie centre of a 

 slip, and examined on a microscope to see that no hairs, cotton-wool, or dust disfigure it, 

 and that it presents the ventral side (if it is not a lateral preparation). (11) The moiety 

 of the turpentine is then removed by means of blotting-paper, taking care that not too 

 much is taken, as otherwise air will enter into the cavities. (12) Canada balsam 

 dissolved in xylol is then applied, and the whole sealed with a cover-glass, which may be 

 pressed down by the weak clip sold for this purpose. These preparations will be di'y 

 enough for use in about two days, and must be carefully studied, so that a good idea of 

 the form and of the relative situation of the parts is arrived at, before proceeding to the 

 separation and dissections which must be undertaken later. The microscopist will 

 require a good high power. I recommend a 7tli of Mr. Pillischer, of New Bond Street, 

 as the best I know of for the purpose, as it is comparatively inexpensive, works at a 

 greater distance than any similar magnification tbat I am acqiuxinted with (which is 

 its peculiar advantage over lenses of higher angular aperture), and gives good definition. 

 With this must be vised a povi'erful substage condenser to enable the light to pierce 

 through the more chitinous parts. 



To study accurately, drawings must be made, and where it is necessary to compare 

 shape and size, those drawings ought to be made on squared j)aper corresponding to 

 squares in the eyepiece of the microscope. 



This is the comparatively easy part of the work ; in what follows the student must 

 not be discouraged by repeated failure, as he has to acquire the steadiness of nerve and 

 nicety of movement necessary for dissecting under the microscope. 



(1) The end of the abdomen must be removed and placed in a drop of water on a live- 

 box or comi)ressorium (the cover being I'emoved), and the organs " teased " apart with 

 the finest needles procurable. The forcipes superiores and inferiores must be separated 

 from their articulated bases, and the penis and its appendages brought out free from its 

 adhering duct and muscles. Place the cover-glass on, and the separated parts can be 

 roughly examined with low and higher powers, and drawn, if desired. The muscles will 

 often be found very hampering and obscuring; a drop of potash solution will facilitate 

 their removal. If this is used, before proceeding further, drop water on the dissections 

 and endeavour to remove the potash as thoroughly as possible ; a little acetic acid will 

 help, but this also must be washed away. 



(2) Take a ^'' cover-glass (thickest size), place a small drop of spirit on it, and place 

 on it the parts, by means of a needle or a bristle. This is very difficult, and the cover- 

 glass must be examined with a lens to judge of success. Care must be taken to avoid 

 the loss of parts by dropping off the needle, &c. Place some more spirit on the glass 

 and place it on a piece of white paper, and both on the hot-plate, which must then be 

 gradually heated. (3) As the spirit evaporates it must be replaced by dropping fresh ; 

 a glass rod drawn to a point answers best. This must be continued till all the water 

 has been driven out of the dissections ; it will sometimes be seen as a milky fluid on the 

 edge of the glass, and can be removed with blotting-paj)er. 



(4) Turpentine must now be dropped on the (by now) hot slide, and allowed partially 

 to evaporate, always dropping fresh before the specimens are dry. Now put out the 



