THE FLY. 35 



object of this is probably, that the third joint, which 

 we shall find to be the most important and delicately 

 organized, should thus be protected from dust and 

 other causes of injury. The principal feature of interest 

 in the antennae is, that the third joint, when mag- 

 nified, is found to be perforated all over with minute 

 punctures ; these are in reality (as a high magnifying 

 power reveals, after the antenna has been bleached 

 with chlorine) a series of microscopic sacculi (Httle 

 sacs) extending inwards, and closed in from the air 

 by a very thin membrane, and between these sacculi 

 there are interspersed on the surface a great number 

 of fine short hairs (PI. VI. fig. 2, a) . Near the base of 

 the joint are three or four larger apertures leading into 

 chambered cavities, protected at the bottom by micro- 

 scopic hairs, and to each of these cavities a nerve has 

 been traced from the brain, showing that they perform 

 some sensory fim^ction. 



What, then, you wiU ask, can be the nature of 

 organs so intricate in their construction as these 

 antennse ? That is a question which naturalists have 

 in vain essayed to answer, and the true fnnction of the 

 feelers is a problem still to be solved. Some zoolo- 

 gists attribute to them the sense of hearing, others 

 of smell, and others again have superadded to the 

 latter sense that of touch. 



These conclusions have been arrived at by com- 

 paring the structure of the antennse in various tribes 

 of insects with their respective habits of life. They 

 have been considered organs of sound chiefly on ac- 



