1440 THE STORY OF THE UNIVERSE 



ception is open to them than to us. Perhaps condi- 

 tions that are appreciable to us only by 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 

 mention, conjecturally, the comparative moisture or 

 dryness of the atmosphere, delicate changes in its 

 temperature, in its density, the presence of gaseous 

 exhalations, the proximity of solid bodies indicated 

 by subtile vibrations of the air, the height above the 

 earth at which flight is performed, measured baro- 

 metrically, the various electrical conditions of the 

 atmosphere; and perhaps many other physical diver- 

 sities which can not be classed under sight, sound 

 smell, taste, or touch, and which may be altogether 

 unappreciable, and therefore altogether inconceiv- 

 able, by us. It is probable, however, that the an- 

 tenna? are the organs in which the sense of hearing 

 is specially seated. 



The forms which are assumed by the antennae 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 antennae 

 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 



