184 EVENINGS AT THE MICKOSCOPE. 



brate animals, — that are far wider spliore of perception 

 is open to them than to its. Perhaps conditions that 

 are appreciable to us only by the aid of the most deli- 

 cate instruments of modern science may bo appreciable 

 to their acute faculties, and may govern their instincts 

 and actions. Among such we may mention, conjec- 

 turally, the comparative moisture or dryness of the at- 

 mosphere, delicate changes in its temperature, in its 

 density, the presence of gaseous exhalations, the prox- 

 imity of solid bodies indicated by subtile vibrations of 

 the air, the height above the earth at which flight is per- 

 formed, measured barometrically, the various electrical 

 conditions of the atmosphere ; and perhaps many other 

 physical diversities which cannot be classed under sight, 

 sound, smell, taste, or touch, and which may be alto- 

 gether unappreciable, and therefore altogether incon- 

 ceivable, by us. It is probable, however, that the mv- 

 tenncB are the oi'gans in which the sense of hearing is 

 specially seated ; a conclusion which has long been con- 

 jecturally held, and which is confirmed by some obser- 

 vations recently made on the analogous organs in tlie 

 Crustacea, which I will allude to more jjarticularly 

 presently. 



The forms which are assumed by the antennce of 

 Insects are very diverse ; and I can bring before you 

 only a very small selection out of the mass. One of 

 the most simple forms is that found in many Beetles, 

 as in this Oardbus for example. Here, each antenna is 

 composed of eleven joints, almost exactly alike and 

 symmetrical, each joint a horny body of apparently a 

 long-oval shape, polished on the surface, but not smooth, 

 because covered with minute depressed lines, and 

 clothed with shaggy hair. Tliere is, however, a slight 



