The Leucospes 



two latter are more substantial and are hol- 

 lowed out like the sides of a groove and, when 

 they are united, form a complete groove in 

 which the filament is sheathed. This bival- 

 vular scabbard adheres loosely to the dorsal 

 part; but, farther on, at the tip of the abdo- 

 men and under the belly, it can no longer be 

 detached, as its valves are welded to the ab- 

 dominal wall. Here, therefore, we find, be- 

 tween the two joined protecting parts, a sim- 

 ple trench in which the filament lies covered 

 up. As for this filament, it is easily extracted 

 from its sheath and released down to its base, 

 under the shield formed by the scale. 



Seen under the magnifying-glass, it is a 

 round, stiff, horny thread, midway in thick- 

 ness between a human hair and a horse-hair. 

 Its tip is a little rough, pointed and bevelled 

 to some length down. The microscope be- 

 comes necessary if we would see its real struc- 

 ture, which is much less simple than it at first 

 appears. We perceive that the bevelled end- 

 part consists of a series of truncated cones, 

 fitting one into the other, with their wide base 

 slightly projecting. This arrangement pro- 

 duces a sort of file, a sort of rasp, with very 

 much blunted teeth. When pressed on the 

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