A82 ANATOMY AND PHYSIOLOGY 



that this is one of the uses to which they are emin- 

 ently subservient. 



Still, however, touch is only a secondary function 

 of the latter ; the generality of authors now agree in 

 regarding them as the appropriate organs of hearing. 

 When a beetle with long antennae is suddenly sur- 

 prised by a loud sound, it stretches these members 

 outwards and holds them immoveable as if listening, 

 and moves them carelessly again when the noise has 

 ceased. They are two in number, in this, as well 

 as in their prominent situation, corresponding to the 

 ears of the vertebrata. On close examination a soft 

 articulating membrane can be detected at their base, 

 beneath which the antennal nerve is conducted; 

 this may be considered as the last vestige of a tym- 

 panum, and the nerve alluded to, as an acoustic 

 nerve. Viewed in this light, the stalk of the anten- 

 nae must be employed to collect the pulses or vibra- 

 tions of the atmosphere and transmit them to the 

 sensorium, an office for which their branched, plu- 

 mose, and other delicate structures all tending to 

 increase the extent of their surface, eminently fit 

 them. This view receives strong confirmation from 

 the circumstance of the auditory organ of the crus- 

 tacea being placed at the base of the antennae, some- 

 times even in the radical joint. It has been wel 

 observed also that the organs in question are almost 

 always very fully developed in such insects as emit 

 sounds as a signal call to the sexes a case in which 

 hearing requires to be more than usually acute 

 Crickets, Grylli, and Cerambycidae, may be given as 



