648 fHE MICROSCOPE. 



but their natural appearance is best preserved by mount- 

 ing in weak spirit and water, or Goadby's solution, using a 

 very shallow cell, to avoid pressure. The spiracles should 

 be dissected out with a fine knife and scissors. 



Mr. Hepwortk's Mode of Preparing and Mounting In- 

 sects. He destroys life with sulphuric ether, then washes 

 the insects thoroughly in two or three waters in a wide- 

 necked bottle ; he afterwards immerses them in caustie 

 potash or Brandish's solution, and allows them to remain 

 in it from one day to several weeks or months, according 

 to the opacity of the insect ; with a camel-hair pencil he 

 then presses the contents of the abdomen and other soft 

 parts dissolved by the potash out in a saucer of clean 

 water, holding the head and thorax with one brush, and 

 gently pressing the other with a rolling motion against the 

 body from the head to the extremities. The potash must 

 afterwards be completely washed out, or crystals may 

 form. The insects must then be dried, the more delicate 

 specimens being spread out or floated on to glass-slides, 

 covered with thin glass and tied down with thread. 

 'When dry, they must be immersed in rectified spirits of tur- 

 pentine, and placed under an air-pump. When sufficiently 

 saturated they are ready for mounting in Canada balsam ; 

 but they may be retained for months in the turpentine 

 without injury. Before mounting, as much turpentine as 

 possible must be drained and cleaned off the slide ; but 

 the thin glass must not be removed, or air would be re- 

 admitted. Balsam thinned with chloroform is then to be 

 dropped on the slide so as to touch the cover, and it will 

 be drawn under by capillary attraction. After pressing 

 down the cover, the slide may be left to dry and to be 

 finished off. If quicker drying be required, the slide 

 must be warmed over a spirit-lamp, but not made too hot, 

 ?,s boiling disarranges the object. Vapours of turpentine 

 or chloroform may cause a few bubbles, but these dis^ 

 appear when condensed by cooling. 1 



\ TRANSFORMATION OP INSECTS. 



The metamorphoses of the insect race offer some of 

 the most curious and wonderful of nature's phenomena for 



(1) Journ. Micros. Soc. vol. i. p. 73. 



