A7T4 N. E. McINDOO 
olfactory pores in other orders of insects; therefore, it is the ex- 
ternal structure that really determines the various types. 
A hypodermal strand (figs. 23, 26, and 28, HypS), running ~ 
from the hypodermis (fig. 25, Hyp) to the chitinous cone (fig. 
26, Con), is always present. In this strand may be observed the 
Figs. 18 to 28 Sections showing internal anatomy of olfactory pores of Musca 
domestica. Fig. 18, from trochanter; figs. 19 to 21, 3 variations on wing; fig. 22, 
portion of cross-section of wing (X 500); fig. 23, largest Hicks’ pores; fig. 24, 
smallest, and fig. 25, largest basal pores, both rows being cut lengthwise; fig. 
26, 4 rows of largest scalpel pores cut crosswise and 1 cut lengthwise; fig. 27, a row 
of smallest scalpel pores cut lengthwise; and fig. 28, from an oblique section of a 
scalpel row of pores, only their external view and nervous connection having been 
drawn. The sense fiber (SF) and hypodermal strand (HypS) are taken from a 
deeper focus. Attention is called to the sense fiber ending at the center of the 
pore aperture. Con, chitinous cone; Hr!, pseudohair; Hyp, hypodermis; N, nerve; 
PorAp, pore aperture; PorlL, pore link; PorR, pore ridge; SC, sense cell, and 
Tr, trachea. X 1000. 
sense fiber (figs. 23, 25, and 28, SF), but it is easily overlooked 
owing to the minute size of these organs. The sense cells in the 
legs and wings (fig. 22, SC) are spindle-shaped as usual, but in 
the halteres (fig. 25, SC) they are more than spindle-shaped 
and assume almost a spherical shape (fig. 29, SC). <A pore 
aperture (figs. 19 and 26, PorAp) was seen only occasionally 
