152 ETKNINGS AT THE mCEOSCOPE. 



crepancy in the detail, and many points not noticed ; — 

 in part, doul)tless, owing to its being auotlier species 

 "wliicli Avas nnder observation, and partly to the infe- 

 riority of the microscopes employed a hundred and fifty 

 years ago, to those we are using. 



In the first place the curve of the/" is diflTerent, 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 square plate, which appears to be slightly 

 concave on its two surfaces, being thickened at its two 

 sides, at each of which, where it is united to the follow- 

 ing plate, it rises and forms with it a prominent ridge 

 running transverse to the course of the saw. Each of 

 these ridges then forms a second tooth, as stout as the 

 main edge-tooth, which, with the rest of the same series, 

 forms a row of teeth on the oblique side of the saw, in 

 a very peculiar manner, difficult to express by words. 

 It is singular that this side of the saw should be studded 

 with minute hairs, since these would seem to interfere 

 with the action of the saw, or at least be liable to be 

 themselves rubbed down and destroyed in its action. 

 But their existence is indubitable ; there they are, 

 pointing at a very acute angle towards the top of the 

 saw. The back edge of the implement bristles with 

 many close-set hairs or spines, forming a sort of brush, 

 but pointing in the opposite direction. 



Each main tooth of the edge-series is cut into one or 

 two minute toothlets on its posterior side (next the base 

 of the saw) and about half-a-dozen on its opposite side 

 (next the tip). The texture is clear and colourless 



