STING STRUCTURE. 
75 
enclose, like a scabbard, the two darts, or lancets), which 
is cleft along its under surface, and terminates in an 
obtuse, but extremely thin, cutting edge. Fig. 35 , b, 
Fig. 34* 
shows the upper part (a) as an enlarged pouch, contract- 
ing at the point (<:), and diminishing gradually to the ex- 
tremity, near which are found teeth, seen enlarged at 
Fig. 35 , H, b. The sheath is double throughout its whole 
extent, the interior space being filled with blood. The 
