converging from the outer wall to the base of the gutter. Both these 
groups can be traced as far forwards as about the base of the ventral 
sclerites. Anterior to this point we have a well-developed band of 
dorso-Iateral muscles stretching from the canal dorsally to the ventral 
sclerites ventrally (fig. 28, j 1 ). 
Muscles of the Labrum. We have also sub-median muscles 
present in the cavity of the labrum stretching from the outer to the 
inner walls (figs. 29, 30, r 4 ). 
Internal Laminae (fig. 28, s 5 ). In sections in the labella 
region, where the dorsal fold is well marked, there appear beneath the 
fold of the integument peculiar yellowish or brownish granular bands, 
of irregular appearance following the outline of the integument. They 
often show little irregular lateral projections. They represent transverse 
sections of plates. They are seen in sections as far as the ventral 
sclerites. They are, moreover, very well developed also in the cavity 
of the labrum in its basal portion. We are unable to suggest what 
may be the function of these bodies. 
MECHANISM OF THE PROBOSCIS 
With regard to the mode of action of these muscles, we consider 
that the function of the longitudinal group is to erect the fork and, 
by so doing, to produce by the traction on the external chitinous wall, 
eversion of the labella and a resulting spread-out condition of the 
teeth. 
I he oblique muscles' function is, we believe, to produce a semi¬ 
rotatory movement of the proboscis 3 (and labella), so that the teeth 
are enabled to exert a cutting action on the skin, the motion being a 
to and fro one. 
The cutting weapon of the proboscis is undoubtedly the teeth. 
These are capable of a variable extent of eversion, and while they arc 
m act ' on die other structures anterior to them, petiolated blades, 
ror -like hairs, etc., are folded back in a plane below the actual tips of 
die teeth, and so escape damage. 
I he tip of the proboscis then can only cut in the everted position. 
" c have in this condition of everted teeth an admirable weapon for 
boring a hole into the skin. The arrangement of a carpenter’s augur 
"ith its cutting flanges on either side is almost an exact parallel, though 
the motion here is a continuous rotatory one, and not a to and fro 
