*79 
narrows as it approaches the ventral margin. In everted sections 
(figs, io, ii) these hairs project dorsally into a pseudo-cavity formed 
by the over-arching wall of the epidermis; and when thus in 
apposition they shut off the cavity of the labial trough. 
(7) Proximal Fringe of Hairs (/>’ in all the figs.). These 
are similar to the former, but occupy a relatively small space on the 
proximal margin. 
LABRUM digs. 14-19) 
This commences immediately behind the fork. Dorsally and 
laterally for its whole length it is covered with spinose hairs directed 
apically. At the apex itself (fig. 16) the hairs are replaced by scales. 
Near the tip, the labrum has ventrally a ridge or chitinous band 
extending across it (fig. 19), on which are situated four hairs evidently 
sensory in function, as nerve endings can be traced into them. 
Behind this point the sides widen slightly and along the interior are 
here arranged in rows, a series of hairs ( a 2 ) on tubercles. 
I he labrum is at first concavo-convex in section, the convexity 
near the tip forming a kind of ridge (fig. 1/). A little further down 
it has the appearance of an U fitted into a V (fig. 18). In the cavity 
between the two there appear early soft structures which later become 
developed into well-marked muscular bands connecting the lateral 
walls of the labrum (figs. 29, 30, j 4 ). The sides of the labrum 
become soon expanded into lateral flaps, which serve the purpose of 
keeping the hypopharynx in its place, the flaps fitting on to the 
expanded sides of the latter (figs. 29, 30). Eventually the ventral 
wall of the labrum becomes closed ventrally, forming now a 
chitinous tube, while the dorsal wall becomes fused and lost in the 
substance of the bulb (fig. 31). 
THE HYPOPHARYNX (b in all the figs.) 
This organ commences at about the same point as the labrum. 
ft is a much smaller and weaker tube. At the extreme tip it appears 
to be membranous in character and to retain no very definite 
constant shape in preserved material. (We would suggest that this 
flaccid condition of the extreme tip is to prevent ingress of fluid, e g., 
blood during feeding, while permitting freely of egress of saliva.) It 
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