108 
DIGESTIVE APPARATUS. 
strong hairs pointing downwards along the edges 
(Fig. 47, a). 
Looking down upon this organ, the disposition of 
the lips will be seen in the cross section through the 
middle (Fig. 48). Fig. 47 is a longitudinal section, 
and shows the narrow slit (^) which communicates 
Fig 47. — Longitudinal Section through Fig. 48. — Cross Section 
Stomach Mouth. of Stomach Mouth. 
with the chyle stomach. In Fig. 48 this slit is cross- 
shaped. Each of the lips is triangular, with the row 
of hairs along its upper edges. The cross opening in 
Fig. 48 gradually assumes a circular shape as it extends 
into the neck, and the gaps at the ends are closed by 
valves. A strong membrane (Fig. 47, c) provided 
with hairs (d) covers the outside of the lips, and can 
be drawn up in folds, as seen in the illustration.^ 
