584 THE SENSES AND SENSORY ORGANS. 
The following special sensory organs have been described : 
1. Special sensory sete intermixed with ordinary tactile and 
protective bristles ; Krapelin. 
2. Olfactory cones (Riechkolben); Leydig, Forel, and Lub- 
bock (Pl. XLI., Fig. 2, C). 
3. Simple pits containing a filiform hair; Lubbock. 
4. Simple pits containing a papilla; Evichson. 
5. Champagne-cork organs; Forel. 
6. Complex cones ; Hauser. 
7. Stethoscope-like organs ; Forel and Lubbock. 
8. Tympanules; Hicks. Simple pits; Krépelin. 
g. Setiferous sacs or canals; Krépelin (Pl. XLI., Fig. 2, B). 
The first five of these are figured by Kripelin, and, although 
he regards them allas modified setz, I think he has disregarded 
a very important fact—the deciduous character of the special 
sensory sete of the antenne. I have observed all the appear- 
ances in the antenna of the Blow-fly, but they result from the 
true setze having been detached, leaving more or less of their 
bases and contents attached to the antenne. Very commonly 
a flame-shaped process, or protoplasmic cone, or only the 
naked axis cylinder remains. Where the base of the seta is 
sunk beneath the surface, a projecting ring of chitin is left in 
the pore canal, giving rise to the champagne-cork-like organ 
of Forel. 
With regard to the complex cones of Hauser, Krapelin was 
unable to find anything like them, although he sought for 
them in the insects in which Hauser described them. They 
are apparently the same thing as the stethoscope-like organs 
of Forel. In the mature insect it is often very difficult, where 
the antennz are very hard, as in the Hymenoptera, to obtain 
sections; hence immature insects, or even nymphs, have been 
used. 
In the Blow-fly nymph the sensory sete of the antenne 
are developed in follicles, and their bases closely resemble the 
bulb of the stethoscope-like organs of Forel. I am inclined 
to regard these as partly developed sensory sete; as, how- 
