10 Ajnerican Quarterly Microscopical Jour?ial. 



fulcrum D, and the flexible, curved arm being straightened, 

 the sheath and attached lancets are projected. 



By an additional contraction of the muscles of C, that piece, 

 turning on o, its only point of attachment to the lever D, tilts 

 over the triangular piece B, on the pivot, s, causing the lan- 

 cet, articulated to its movable arm at c, to slide along e, b, 

 and thus project its point into the wound beyond the sheath. 



The beautiful and effective mechanism of this lever of the 

 third class, by means of which the lancets are thrust deep into 

 the incision first made by the point of the sheath, will, perhaps, 

 be better understood from Fig. lo. This figure represents the 

 levers of one side with a detached arm of the sheath and a 

 piece of the lancet. 



The form of the lever, D, is shown by the line, k, o, n, m, 

 this lever being articulated to the arm at n. The broad lever, 

 C, whose outline is denoted by x, i, o, k, with its anterior side 

 beyond k, o, overlapping D, is articulated by a ligament to D, 

 at the point o, and turning on this point, changes its position 

 to that denoted by the dotted line of the same form, strikes its 

 angle, i, against the triangular piece, which is also articulated 

 to D, near o, and throws its movable arm, which curves over 

 the arm of the sheath to its attachment with the lancet at e, 

 to the position denoted by the dotted outline of that piece 

 moving the end of the lancet, a to a'. 



Fig. I, E E, are two pieces attached to the levers, D D, 

 and resembling, in every respect, the organs of sense ap- 

 pended to the head of many insects, and called palpi, or feelers. 

 That they here serve the same purpose is shown by the fact 

 that they are always protruded in advance of a thrust made 

 by the sting, as if to ascertain the location or character of an 

 object of attack. 



The name sheath, applied to the principal piece used for 

 making an incision, is a somewhat misleading term, for it can 

 hardly be said to enclose the lancets in any part of its course, 

 as may plainly be seen by inspecting the transverse sections; 

 but I have deemed it best to adopt the English name by which 

 it is most generally described. " Gorgeret " or Gorget applied 

 to this piece by Lacaze Duthiers from its resemblance to the 

 surgical instrument of that name, is -much more appropriate, 

 but would necessarily lead to the adoption of the entire nomen- 

 clature of that author, which, though unquestionably more in 



