6oo 



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 M tiller, 

 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. M tiller first described the tympanic ap- 

 paratus in the Acrididae, 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 



FIG. 76. Details of the Miillerian organ, after Graber [283]- 



A. The Miillerian ganglion (;), and a small portion of the tympanic mem- 

 brane (nit) of Pachylylus 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 Muller's fluid. 



nerve ganglion surmounted by a group of chordotonal organs, 

 and enclosed in a minute sac filled with iluid. It has been 

 aptly compared with the membranous labyrinth. 



Siebold's Organ is much more complex than Muller's, which 

 is frequently quite rudimentary. It consists of two parts, which 

 I shall term the bulb and the crista. The bulb closely resembles 



