Figs. 19 to 26 Sections, showing detailed structure of chordotonal organ and 

 ganglion cells. Fig. 19, semidiagrammatic drawing from several longitudinal 

 sections through anterior portion at proximal end of hind tibia of a drone, twenty- 

 one days old, showing chordotonal organ suspended in blood chamber, but at- 

 tached at both ends to hypodermis {Hyp) ; X 320. Fig. 20, longitudinal view of 

 one of the sensory elements from fig. 19, showing following parts in detail; sense 

 cell {SC), axial tube {Ax), enveloping cell {EC), axial fiber {AF), cone {Con), 

 cap cell {CC)j and nuclei {Nuci, Nuci and Nuc%) of sense cell, enveloping cell 

 and cap cell, respectively. Fig. 21, cross-section of sense cell {SC) through 

 nucleus, showing tail end (large dot) of axial tube; figs. 22, 23, and 24, cross- 

 sections of proximal end, of middle portion through nucleus, and of distal end, 

 respectively, of enveloping cell, showing appearance of axial tube {Ax) and its 

 fiber^(AF). Fig. 25, longitudinal section, and fig. 26, cross-section of ganglion 

 cells from tibia of a drone. Figs. 20 to 26, X 1000. 



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