192 N, E. McINDOO 



of the branches gives off fibers to some tactile hairs (fig. 14, THr) 

 and also a smaller branch which innervates the olfactory pores 

 {For) and the chordotonal organ (0). Schon calls this small 

 branch (figs. 14 and 19, SN) thesubgenual nerve (Subgenualnerv), 

 It runs into the sense cell group and gives off a fiber to each 

 individual sense cell (fig. 19, SC), The spindle- but sometimes 

 diamond-shaped sense cells lie in a mass which extends diagonally 

 half-way across the blood chamber. In all of the present writer's 

 sections, the organ is anchored at the base of the sense cell group, 

 but only occasionally was it also fastened at the other end of the 

 organ. According to Schon, it arises from the distal end and 

 should always be fastened at this end. The distal end of a sense 

 cell is terminated into a long, slender, sac-hke enveloping cell 

 {EC, Umhlillungszelle) whose elongated nucleus (Nucz) some- 

 times nearly fills the entire lumen of the cell. Running the full 

 length of the enveloping cell there is a dark-staining thread, the 

 axial tube (Ax), which ends in a much darker staining body, the 

 cone {Con, Stift), lying in the proximal end of the large oblong 

 or pear-shaped cap cell {CC, Kappenzelle) whose nucleus {Nucz) 

 usually lies in the distal end. 



The walls of the axial tube correspond to the extended walls 

 of Schon's Stift. Schon also describes two other types of cells 

 which the present writer has not been able to differentiate from 

 those just mentioned. His accessory cells (akzessorische Zellen) 

 he between the cap cells and his end fibers (Endfasern), which 

 fasten the organ to the hypodermis, 



A more careful study of the sensory element of the chordotonal 

 organ under a magnification of 1900 diameters shows the foUow- 

 ing: Lying around the conspicuous nucleus (figs. 19 and 20 

 Nuc) of the sense cells {SC) there are large dark-staining particles' 

 the largest one of which seems to be the tail end of the axial 

 tube {Ax). In longitudinal sections this particle appears as a 

 dark streak and may or may not reach as far as the nucleus In 

 cross-sections it appears as a large, dark, solid particle (fig' 21) 

 Cross-sections through the proximal end (fig. 22), middle portion 

 (fig. 23), and distal end (fig. 24) of the enveloping cell (EC) 

 show that instead of the axial tube continuing very far as a rod 



