INSECTS: THEIR EARS AND EYES 187 



the aid of the most delicate instruments of modern science 

 may be appreciable to their acute faculties, and may gov- 

 ern their instincts and actions. Among such we may men- 

 tion, conjecturally, the comparative moisture or dryness of 

 the atmosphere, delicate changes in its temperature, in its 

 density, the presence of gaseous exhalations, the proxim- 

 ity 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 altogether 

 unappreciable, and therefore altogether inconceivable, by 

 us. It is probable, however, that the antennae are the or- 

 gans in which the sense of hearing is specially seated; a 

 conclusion which has long been conjecturally held, and 

 which is confirmed by some observations recently made 

 on the analogous organs in the Crustacea, which I will 

 allude to more particularly 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 Carabus, 

 for example. Here each antennce 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. There is, 

 however, a slight illusion in the appearance: it seems as 

 if the dividing point of the joints were, as I have just said, 

 at the termination of the oval, but when we look closely 

 we see that the summit of each oval is, as it were, cut off 



