402 Mr. H, Eltringham on the 
slightly granular appearance and shows a varying number 
of nuclei. Scattered globules of the secretion are also seen. 
It should here be noted that Dr. F. Miiller and later, 
independently, Dr. F. A. Dixey, discovered in Satyrines 
and Pierines, respectively, special distributions of tracheae 
in connection with the scent patches in butterflies belonging 
to those genera. I have not found such structures in 
Amauris niavius. 
The abdominal brushes. 
The position of these in the body of the insect may be 
understood from fig. 1, which represents a dissection of 
the genital armature viewed from above, with the brushes 
am situ. In the lower part of the centre of the figure is 
seen the penis, with its two great extensor muscles, passing 
through the proximal dorsal membrane of the uncus. The 
latter is a large arched chitinous plate with a prominent 
ridge in the centre of its dorsal surface, and on either side 
of this ridge lie the brushes. Each brush is contained in a 
membranous bag, the proximal end of which is provided 
with a muscle attached to one of the sternites. The hairs 
of which the brush is composed arise mainly from the 
proximal end of the bag. The membrane at the opening 
of the latter is continuous with the liming membrane of 
the tergite. The bag is everted, doubtless by means of 
fluid pressure, and the process may be compared with the 
turning inside out of a glove finger. The brush hairs then 
project from the posterior end of the insect, forming, when 
completely everted, a more or less spherical tuft. The 
whole apparatus can be withdrawn by the contraction of 
the retractor muscles shown in the figure. A microscopic 
examination of the brushes and their containing mem- 
branes reveals the following structure. The hairs of each 
brush are in two tufts. One, the larger, is composed of 
yellowish hairs, the sockets of which are placed at the 
base of the bag. The second tuft consists of black hairs 
arising from similar sockets placed somewhat more distally 
and on one side of the bag. 
Fig. 8 shows a section of the brush bag at its base. The 
hairs arise from a thick layer of elongated cells having 
nuclei at their bases and chitinous sockets at their ex- 
tremities. Fig. 6 shows three of the hairs with cells 
attached. The ae difference I can find between the 
