POSITION OF AUDITORY RODS. 



105 



notes, as is the case with the series of diminishing 



arches in the organ of Corti (ante, p. 80) of our own ears. 



I have already alluded to the supra-tympanal 



ganglion; this also terminates in a number of vesicles 



Fig, 67.— Diagram of a section through the auditory organ of a Grasshopper (Meco- 

 nema). c, cuticle; a.r, auditory rod; ax, auditory cell; tr, trachea?. 



containing auditory rods, which are said to be somewhat 

 more elongated than those in the organ of Siebold. 



The arrangement of the organ is very curious, and 

 will best be understood by reference to Fig. 68. 



The great auditory nerve, as already mentioned, 

 bifurcates almost immediately after entering the tibia, 

 and one of the branches swell into a ganglion : from 

 this ganglion proceed fibres which enlarge into 

 vesicles (Fig. 68), each containing an auditory rod ; and 

 then again contract, approximate into a close bundle, 

 and coalesce with the hypoderm (inner skin) of the 

 wall of the tibia. The supra-tympanal organ of the 

 crickets closely resembles that of the grasshoppers, 

 while, on the other hand, they appear entirely to want 

 the organ of Siebold (Fig. 65). This is a very remark- 

 able difference to exist in two organs otherwise so 

 similar. 



There appear to be two ways in which the atmospheric 



