132 EVENINGS AT THE MICROSCOPE. 



combines at the same time the properties of a saw and 

 of a rasp or file. So far as we are aware, these two 

 properties have never been combined in any of the tools of 

 our carpenters. The rasping part of the ovipositor, how- 

 ever, is not constructed like our rasps, with short teeth 

 thickly studded together, but has teeth almost as long as 

 these of the saw, and placed contiguous to them on the 

 back of the instrument, resembling in their form and 

 setting the teeth of a comb." * 



Now look at this object which I have just extracted 

 from the abdomen of a rather large female Saw-fly, of a 

 bright green hue spotted with black. The first portion of 

 the apparatus that protruded on pressure was this pair of 

 saws of an y^like figure. These agree in general with 

 those described ; here is in each the doubly-curved blade, 

 the strengthened back, the rasp-like jagging of the lateral 

 surfaces, the teeth along the edge, and the secondary 

 toothlets of the latter. All these essential elements we 

 see, but there is much discrepancy in the detail, and 

 many points not noticed ; in part, doubtless, owing to its 

 being another species which was under observation, and 

 partly to the inferiority of the microscopes employed a 

 hundred and fifty years ago to those we are using. 



In the first place, the curve of the / is different, the 

 convexity of the edge being towards the point and the 

 concavity nearest the base. Then the strengthening does 

 not appear to me a groove in which the saw plays, but 

 a thickening of the substance of the back. Each main 

 tooth of the saw in this case is the central point in the 

 edge of a square plate, which appears to be slightly con- 

 cave on its two surfaces, being thickened at its two sides, 

 at each of which, where it is united to the following plate, 

 it rises and forms with it a prominent ridge running trans- 

 versely to the course of the saw. Each of these ridges then 

 forms a second tooth, as stout as the main edge-tooth, 

 * " Insect Architecture," 153. 



