116 CEPHALOCHORDATA CHAP, 
epithelial cells (see Fig. 72, p. 118), some of which bear sensory 
processes, while others have a striated cuticular border. There 
is no general ciliation of the surface in the adult. 
The true mouth is a small pore at the bottom of a large 
vestibule (the stomodaeum), placed at the anterior end of the 
Ny 
Fic. 71.—Diagram of the anatomy of Amphioxus. A, anterior; B, posterior part. 
an, Anus ; atr, atrium ; atr’, its posterior prolongation ; arp, atr ioporey 3 Ors Drain 
br.cl, branchial clefts ; br,f, brown funnel ; 67.sep.1, primary, 67.sep.2, secondary 
branchial lamella ; 67.7.1, primary, 07.7.2, secondary branchial rod ; caud.f, caudal 
fin ; cent.c, central canal ; cir, cirri ; coel, coelom ; dors,f, dorsal fin ; dors.f.r, dorsal 
fin-ray ; en.coe, cerebral vesicle; e.sp, eye-spot; gon, gonad; int, intestine; 77, 
liver ; mth, mouth; myom, myotomes; nch, notochord ; nph, nephridia ; olf.p, 
olfactory pit ; or, fd, oral hood ; ph, pharynx ; sh, skeleton of oral hood and cirri 
(dotted) ; sp.cd, spinal cord ; vent. f, ventral fin ; vent,f.r, ventral fin-ray ; vl, velum ; 
vi.t, velar tentacles. (From Parker and Haswell.) 
ventral surface (Figs. 70 and 71), and formed by the “ oral hood,” 
which may be a prolongation forwards of the atrial or meta- 
pleural folds at each side. The edges of the oral hood bear 12 to 
20 pairs of cirri (Fig. 70, cir) or ciliated tentacles (strengthened 
by skeletal rods), which form a sensory fringe around the open- 
ing. The anus (Figs. 70 and 71, an), is asymmetrical, being 
a ee 
