1884.] The Structure of the Trachee of Insects. 569 
the housefly, some years ago, I made a discovery, the important 
bearings of which were easy to appreciate ; but I did not refer to 
it in the paper then issued, as I wished to test it more fully. I 
found that the scraping-tubes (pseudotrachez) of this organ are 
flanked by chitinous thickenings of the cuticle, that these thick- 
enings are enfolded or wrinkled so as to resemble the C-like 
semitubes which serve as an inner skeleton for the pseudotrachee. 
The enfolded parts can be flattened out with the needle, and 
when liberated they at once spring back to 
their normal crenulated condition (Fig. 1, 
C). This suggests that the psexdotrachee 
(P) are likewise thickened crenulations of the 
chitinous membrane with which they are 
continuous.! 
This doctrine receives unexpected sup- is 
port from Kraepelin’s elaborate paper, 
just published, on the proboscis of Musca2 
pelin accepts the views published by 
myself, and confirmed by Dimmock, as to 
Hd of the anatomy of its parts. He pig, r—From distipro- 
aso adopts the explanation of its protru- boscis of housefly (Musca 
tracheze, and likewise that these roots them- *” inserted in a transverse 
Selves, are formed by secondary foldi f j 
y foldings o 
membrane, If he had followed out this observation he would 
Ome to the conclusion that the entire pseudotracheæ, be- 
py patios at the outset, are so throughout. This is the 
cams that I formerly reached, as stated above, from an in- 
: leg line of investigation, and hence I may take it as 
| E oer, so long a subject of interest, have 
explanation. 
iP 
a i 
> eg ption of these parts see my paper on the “ Proboscis of the House- 
3 i 
- me or two rows of 3-cusped teeth 
