136 EVENINGS AT THE MICROSCOPE. 



two inner lancets seem to be united in one, in Reaumur's 

 species, or else, which I think more probable, he did not 

 succeed in separating them. 



He describes the two curved spoon-shaped pieces as 

 finely indented on both sides with teeth, which are strong, 

 nine in number, arranged with great symmetry, increas- 

 ing in fineness towards the point. This instrument he 

 describes as composed of three pieces, the two exterior, 

 which he calls the files, and another pointed, which he 

 compares to a lancet, which is not toothed. "The files 

 are capable of being moved forward and backward, while 

 the central one remains stationary ; and as this motion 

 can be effected by pressing a pin or the blade of a knife 

 over the muscles on either side at the origin of the 

 ovipositor, it may be presumed that those muscles are 

 destined for producing similar movements when the 

 insect requires them. By means of a finely-pointed pin 

 carefully introduced between the pieces, and pushed 

 very gently downwards, they may be, with no great 

 difficulty, separated in their whole extent. 



" The contrivances by which those three pieces are held 

 united, while at the same time the two files can be easily 

 put in motion, are similar to some of our own mechanical 

 inventions, with this difference, that no human workman 

 could construct an instrument of this description so 

 small, fine, exquisitely polished, and fitting so exactly. 

 We should have been apt to form the grooves in the 

 C9ntral piece, whereas they are scooped out in the 

 handles of the files, and play upon two projecting ridges 

 in the central piece, by which means this is rendered 

 stronger. M. Reaumur discovered that the best manner 

 of showing the play of this extraordinary instrument is 

 to cut it off with a pair of scissors near its origin, and 

 then, taking it between the thumb and the finger at the 

 point of section, work it gently to put the files in 

 motion. 



