192 N. E. McINDOO 
of the branches gives off fibers to some tactile hairs (fig. 14, T’H7) 
and also a smaller branch which innervates the olfactory pores 
(Por) and the chordotonal organ (O). 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 le 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-like enveloping cell 
(EC, Umbiillungszelle) whose elongated nucleus (Nuc.) 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 (Aw), 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 (Vues) 
usually lies in the distal end. 
The walls of the axial tube correspond to the extended walls 
of Schén’s Stift. Schén 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) 
lie 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 follow- 
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 (Az). 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 (£C) 
show that instead of the axial tube continuing very far as a rod, 
