184 EVENINGS AT THE MICROSCOPE. 



commentator appears to have as little suspected its pre- 

 sence. This pair of saws that we have been looking at is 

 but the sheath of a still finer pair of lancets or saws, 

 which you may see here. These are much more slender 

 than the former, and are peculiar in their construction. 



INNER SAW OF SAW-FLY. 



Their extreme tip bears only saw-teeth, and these are 

 directed backwards; but one side of the entire length 

 presents a succession of cutting edges, as if a number of 

 short pieces of knife-blade had been cemented on a rod, 

 in such a manner as that the cutting edges should be 

 directed backwards, and overlap each other. The other 

 lateral surface is plain, and both are convex in their 

 general aspect. The appearance of these implements is 

 very beautiful, for the texture is of a clear pale amber, but 

 the structure is strengthened by a band which runs along 

 each edge, and by transverse bands crossing at regular 

 intervals, of a denser tissue; and these are of a rich golden 

 translucent brown. 



From the construction of this implement I should infer 

 that its force is exerted by pulling and not by pushing ; 

 the direction of the teeth and of the cutting plates shows 

 this. The sharp horny point is probably thrust a little 

 way into the solid wood or bark, and then a backward pull 

 brings the teeth and cutting plates to act upon the 

 material, and so successively. And probably these points 

 are the first parts of the whole apparatus that come into 

 operation ; the blunter saws of the sheath serving mainly 



