192 



NATURAL HISTORY. [CH. XIII. 



organization. As soon as it is known what is under 

 these windows, it appears probable that the two 

 cells, and the membranes so accurately extended in 

 them, are destined to modify those sounds, which, 

 however inharmonious to our ears, are doubtlessly 

 pleasant music to those for whom they are intended. 

 The transparent membranes have been supposed by 

 many to be a kind of drum, which, being struck, 

 produces the peculiar sound of the cicada. Never- 

 theless, none of the parts already described are the 

 true organs, for these are only to be seen when the 

 dissection of the insect is made from the back. The 

 two strong muscular bands are attached to two hol- 



low, uneven, membranous bodies,/. When the mus- 

 cles contract, the membranous bodies, which are 

 fixed, become indented in some part of their circum- 

 ference; and when the muscles are relaxed, the 

 part resumes its former shape ; and it is by this play 

 of an elastic membrane, which becomes alternately 

 concave and convex, that the peculiar sounds of this 

 insect are produced. The air, agitated by the mem- 



