A UDITOR Y AND SO UND-PROD UCING MECHANISMS. 597 



chordotonal organ may contain one or many, 10 to 20 or more, 

 auditory rods, forming a fasciculus : when more than one rod 

 is present there is a ganglion in place of a single nerve-cell. 



The Auditory rods are minute, more or less fusiform organs, 

 consisting of a body terminating in a long, fine, straight thread, 

 unipolar rods (Mononcmatischc Stifte}, or each end of the body 

 may have a rod or thread-like prolongation, when the organ is 

 bipolar (Aniphinematische Stifte). The second prolongation is 

 always distal, and may be represented in the unipolar rods by 

 the short conical point. 



I have never found primitive chordotonal organs either in 

 the imago or larva of the Blow-fly. 



Poriferous Chordotonal Organs. Graber applies this term to 

 certain organs at the bases of the halteres of the Diptera, and 



FIG. 73. Three chordotonal end organs, after Graber : A, the quasi-chitinous rod 

 and bulb of the unipolar variety ; B, a group of unipolar end organs, from a 

 larva of Tabanus autumnalis ; C, a bipolar chordotonal end organ, from a 

 Syrphus larva ; ch, head of the auditory rod ; c, pyramidal prolongation in the 

 unipolar variety ; g , ganglion cells ; t, proximal, and (', distal end of the chordo- 

 tonal thread. 



on the wing nervures of insects. These are essentially chordo- 

 tonal organs, somewhat modified in their minute structure, in 

 which the capitate extremity of the rod is in relation with a 

 thin plate, or pore, in the epidermis, or with the base of a 

 specially modified seta. These will be more minutely described 

 with the halteres (p. 609). 



The tympanic chordotonal nerve-terminals are treated of on 

 p. 600. 



Graber's Views on the Stimulation of Primitive Chordotonal 



