164 ZOOLOGY 
into the body-cavity. At their upper ends the sacs are attached 
to the body-wall, and open to the exterior a little in front of 
the level of the anus. Each sac consists of two portions: a 
posterior glandular part lined by large glandular cells, which 
give off vesicles containing their excretion, and a muscular 
non-glandular anterior half, which opens both on to the 
Fie. 105.—Diagram showing 
relation of nervous system, vas- 
cular system, and oesophagus in 
Phymosoma varians. Partly 
after Selenka. 
1. The brain, represented rela- 
tively too small. 
2. Nerves to skin of preoral lobe. 
3. Lophophore ; each tentacle is 
represented by its blood 
sinuses and its nerve. 
4, Blood sinuses of lower lip. 
Or 
Oesophagus. 
Dorsal blood-vessel. 
Su ge 
Ventral nerve cord. 
exterior and into the coelom. The opening into the latter 
space is situated close to the external opening, and is guarded 
by a frilled, funnel-shaped lip, thickly ciliated. The wall of 
the organ contains many muscle fibres, and it is capable of 
considerable change of form. 
The nervous system consists of a bilobed brain in con- 
tinuity with the epidermis of the concavity of the lophophore 
(Fig. 105). It gives off a pair of lophophoral nerves, which 
run along the base of the tentacles, sending off a nerve into 
