600 THE SENSES AND SENSORY ORGANS. 
several different end organs, in relation with the tympanic 
apparatus. Three forms of end organs have been described, 
of which two, or even all three, are frequently present in the 
same insect. These special structures are the organ of Miiller, 
the organ of Siebold, and the supratympanic organ, discovered 
by Graber, which may be termed the organ of Graber. These 
structures are situated at the extremity of a large nerve which 
springs from the thoracic ganglion. 
Muller's Organ.—Miiller first described the tympanic ap- 
paratus in the Acridide, and discovered a ganglionic structure 
situated upon the inflected angle of the tympanic sclerite. 
This organ has been carefully described by Siebold, Leydig, 
and more recently by Graber; it is undoubtedly a terminal 
Fic. 76.—Details of the Miillerian organ, after Graber [283]. 
A. The Miillerian ganglion (7), and a small portion of the tympanic mem- 
brane (#¢) of Pachytylus stridulus, showing the two processes of the tympanic 
sclerite which project from its inner surface. Their position in the figure is due 
to displacement in the process of mounting the specimen. 
B. A portion of the Miillerian ganglion of Acridium tartaricum., From a 
specimen teased out in Miiller’s fluid. 
nerve ganglion surmounted by a group of chordotonal organs, 
and enclosed in a minute sac filled with fluid. It has been 
aptly compared with the membranous labyrinth. 
Siebold’s Organ is much more complex than Miiller’s, which 
is frequently quite rudimentary. It consists of two parts, which 
I shall term the bulb and the crista. The bulb closely resembles 
