214 THE INTEGUMENTAL SKELETON OF THE IMAGO. 



drop of balsam on a cover, and invert it on the object ; the 

 thick balsam protects it from the pressure of the cover. 



If the object is at all thick, I previously place a small slip of 

 glass of suitable thickness on either side of it to support the 

 weight of the cover. 



Mr. Karop, who has mounted some very beautiful specimens, 

 adopts the following method : 



His practice is to soak the chitinous parts in weak glycerine 



glycerine and water — and to transfer them to stronger 



solutions of glycerine, and at last to pure glycerine. He makes 

 his cells of Miller's caoutchouc cement, turns a thin layer of the 

 same on the top of the cell, and has a cover smeared with 

 glycerine ready. He then puts the specimen into the cell with 

 more than sufficient glycerine to fill it, but not too great an 

 excess, and turns the cover over it gently, beginning at one edge, 

 and gradually lets it down, so as to drive the surplus glycerine 

 out at the side. This particular cement is not affected by the 

 glycerine, and the glass cover adheres to the cell firmly in 

 a day or two. He then cleans off the surplus glycerine with a 

 brush and water, allows the slide to dry, and turns a ring of 

 cement over the junction of the cell and cover, repeating this 

 in a day or two. Such specimens keep well ; some I have 

 are ten years old, and are still perfect. 



