AUDITORY AND SOUND-PRODUCING MECHANISMS. 597 
chordotonal organ may contain one or many, Io 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 (Mononematische Stifte), or each end of the body 
may have a rod or thread-like prolongation, when the organ is 
bipolar (A mphinematische 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 
Fic. 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; ¢, 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 
