374 Prof. A. M. Mayer's Researches in Acoustics. 



which there is not the least trace. The two white convex spots 

 at the base of the antenna? of Blatta orientalis, and which Tre- 

 viranus has described as auditory organs, are, as Burmeister has 

 correctly stated, only rudimentary accessory eyes. Newport and 

 Goureau think that the antennas serve both as tactile and as 

 auditory organs. But this view is inadmissible, as Erichson 

 has already stated, except in the sense that the antennas, like all 

 solid bodies, may conduct sonorous vibrations of the air ; but 

 even admitting this view, where is the auditory nerve ? for it is 

 not at all supposable that the antennal nerve can serve at the 

 same time the function of two distinct senses.) 



" Certain Orthoptera are the only Insecta with which there 

 has been discovered in these later times a single organ having 

 the conditions essential to an auditory apparatus. This organ 

 consists, with the Acrididse, of two fossae or conchs, surrounded 

 by a projecting horny ring, and at the base of which is attached 

 a membrane resembling a tympanum. On the internal surface 

 of this membrane are two horny processes, to which is attached 

 an extremely delicate vesicle filled with a transparent fluid and 

 representing a membranous labyrinth. This vesicle is in con- 

 nexion with an auditory nerve which arises from the third tho- 

 racic ganglion, forms a ganglion on the tympanum, and termi- 

 nates in the immediate neighbourhood of the labyrinth by a 

 collection of cuneiform staff-like bodies with very finely pointed 

 extremities (primitive nerve-fibres ?), which are surrounded by 

 loosely aggregated ganglionic globules. (This organ has been 

 taken for a soniferous apparatus by Latreille. J. Miiller was 

 the first who fortunately conceived that with GryUus hierogly- 

 phus this was an auditory organ. He gave, however, the inter- 

 pretation only as hypothetical; but I have placed it beyond all 

 doubt by careful researches made on Gomphoceros, CEdipoda, 

 Podisma, Cahptenus, and Truxalis.) 



"The Locustidse and Achetidse have a similar organ situated 

 in the fore legs directly below the coxo-tibial articulation. 

 With a part of the Locustidse (Meconema, Barbitistes, Phanero- 

 ptera, Phylloptera), there is on each side of this point a fossa, 

 while with another portion of this family there are at this 

 same place two more or less spacious cavities (auditory cap- 

 sules) provided with orifices opening forward. These fossas 

 and these cavities have each on their internal surface a long- 

 oval tympanum. The principal trachean trunk of the leg 

 passes between two tympanums, and dilates at this point into 

 a vesicle whose upper extremity is in connexion with a gan- 

 glion of the auditory nerve. This last arises from the first 

 thoracic ganglion, and accompanies the principal nerve of the 

 leg. From the ganglion in question passes off a band of ner- 



