176 
Ventral Flanges or Lips ok the Labella ( c 2 mall the 
figs ). These are extremely thin and flexible but are strengthened by 
several rows of strongly chitiniscd scales, of which the external row is 
much the larger. When the labella are closed these flanges or lips 
meet together and completely enclose the .nternal mouth-parts 
(fig. iq) ; but when eversion takes place they occupy a dorso-lateral 
position, and the edges are then projected upwards and dorsalwanh 
(figs. 2. 3, jo, 11 ), resting practically on the sub-lying chitin of the 
external wall. 
The Fork (e in all the figs.). A proboscis mounted in thi 
dorso-ventra! position, as in fig. 5, shows at the base of the cleft, 
solid clntinous median structure, the axial apophysis (q), and somera 
e " n t ^ 1 ’ s a L -shaped piece of chitin, the fork, with its concavit) 
pening forward. With this, are seen articulating two lateral sclerite 
(figs- 5 . 6, e l ) and posteriorly two ventral sclerites (figs. 5, 6, /). Thf 
f • ' ct ') < - en the base of the fork and these ventral sclerites i; 
I ringed with rows of hairs (fig. 6, f l ). 
• ^ P ' Ca ^ dl ° Pork ’ wkick is. as we shall see, an internal structure, 
extern ^ ^ anges (%• 5 ). which are continuous with the 
sclerite • Lalerall >" the fork articulates with the two lateral 
direedv^er S r SeCti ° n in ** 2 5 - A These lateral sclerites are 
this cormeebor^m/b" 0 ' 0 ^ ^ chhinoUS inte gument, so that by 
fork is enabled to n ° f . t,,e d,rect continuity at its tips, the 
by the powerful °i U< ° evers,on of the labella when acted upon 
the arms of the ^ ° the bu,b - Stretching across between 
is first seen when the hind * hT. ° f f ' bv ° US tissue ( f, g 2 5 > This 
band serves to strenp+1 T ° ^ aX,aI a P°P h X sis disappears. This 
to the fibrous tic«s, ^ armS ol t,ie fork - and by its attachments 
Peg itself when the T the peg " ,les must exercise traction on the 
Position of the hh 11 ^ ta<eS the verticaI position. In the everted 
and this organ is S0C dlat we i° se this appearance of a fork. 
1 ids change of nositi' ° Stretc ^ 1I ' n & across almost as a band (fig. 3-4 
dorsally and nosti- ■ °?’ S la ^ Sce ’ ,s P r °duced by the tips moving 
section the *> that now in a transverse 
transversely (fig S -, r * S * cn £ tk ( b g- 12) instead of being cut 
b e seen (fig. 6s) whi ’,~ 2) n cIear ed specimens also the tendons can 
* Ch attached “> fork a, its tips (fig. 3. 4 
