72 EVENINGS AT THE MICROSCOPE. 



right, to the left, and in all directions, that this bird of 

 rapid flight and ready evolution was unable to overtake 

 and capture it, the insect eluding every attempt, and being 

 in general fully six feet in advance of the bird. A Dragon- 

 fly has been known to fly on board a ship at sea, the 

 nearest land being the coast of Africa, five hundred miles 

 distant, a fact highly illustrative of its power of wing. 



It is a point of interest to know the structure of the 

 organs by which such results are accomplished, and there- 

 fore we will devote an hour to the microscopical examina- 

 tion of the wings of one or two insects. Let us begin 

 with the common Fly, one of which, a fine blue-bottle, is 

 somewhat noisily buzzing in the window ; 



" The blue-fly sung i' the pane," 



as if to invite our attention to him. Well, we will borrow 

 one of his wings for the lesson ; and, putting it into the 

 stage-forceps, we shall be able to turn it in any direction 

 for observation beneath the microscope. 



At first it seems a very thin transparent membrane, of a 

 shape between triangular and oval, with a few fine black 

 lines running through it, and along one edge. But on 

 bringing a greater magnifying power to bear on it, we see 

 that the clear surface is covered with minute short stiff 

 hairs, each of which has an expanded base. And still 

 further, by delicate focussing, we find that there are two 

 sets of these hairs, which come into view alternately, those 

 of one row projecting upward towards our eye, those of the 

 other downward. They are placed on both the upper and 

 under surfaces, and are in fact appendages of two distinct 

 membranes, applied to each other. There is some reason 

 to believe that these hairs are delicate organs of touch 

 communicating impressions through the skin to a sensitive 

 layer beneath ; at least such seems their function on the 

 body, and we may judge from analogy that it is not 

 different here. 



