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ANNUAL REPORT SMITHSONIAN INSTITUTION, 1923 



ported by the pear-shaped nodule (P) of the tympanum. The cells 

 directly attached to the peg form a thick outermost layer of large 

 cells called the cap cells (OCl). Internal to them is a region of 

 slenderer cells containing minute, brownish, peg-shaped rods known 

 as the scolopalse (Sco). The basal part of the organ consists of a 

 mass of oval cells called the sense cells (SCls) because their inner 

 ends are in direct continuity with fibers of the nerve (Nv). The 

 branch of the sense body swells at its middle to a spindle-shaped 

 thickening containing the same elements as the other part, viz. long- 



EC1 



CC1 



A 



Fig. 35. — The "auditory organ" of the front leg of Evcticus, a member of the katydid 

 family (simplified from Schwabe). A, cross-section of the leg through the auditory 

 organ, showing the ear slits (e) leading into the large ear cavities (E, E) with the 

 tympana (Ttn, Tm) on their inner faces. Between the tympana are two tracheae (Tra, 

 Tra) dividing the leg cavity into an upper and a lower channel (BG, BG). The 

 sensory apparatus forms a crest on the outer surface of the inner trachea, each ele- 

 ment consisting of a cap cell (GCl), an enveloping cell (ECl) containing a scolopala 

 (Sco), and a sense cell (Scl). Ct, the thick cuticula. forming the hard wall of the leg. 

 B, surface view of the "crest " of the trachea, showing the sensilla graded in size 

 from above downward. The sense cells (Scl) are attached to the nerve (Nv) along 

 the inner side of the leg 



necked cap cells (CCl) attached to the support (P), and proximal 

 cells containing scolopalae (Sco) and prolonged basally to the sense 

 cells. 



It is evident that the essential parts of this organ must be the sco- 

 lopalae since they are the only distinctive structures in it. These 

 rods may be separated from the enveloping cells by gently dissect- 

 ing and crushing the sense body, and one so isolated is shown at 

 G of Figure 34. The detail structure of a scolopala and its inclos- 

 ing cells, as described by Schwabe, is shown at D, E, F, and G. 

 The scolopalse (Z>, Sco) and a large vacuole (Vac) at its base are 

 contained in the enveloping cell (ECl). The vacuole, according to 



