PHYLUM CHORDATA 



397 



to secrete a digestive fluid similar to that produced by the liver 

 in the vertebrates. The intestine leads directly to the anus (an). 



ccnt.c 



' h dorsfr coel yyom orf 



ct-orsf 



E. 



brsep.-j 





'jTilijiiH;^?' ■ 



x'cnl 



Fig. 343. — Diagram of the anatomy of Amphioxus. A, anterior, 

 B, posterior part, an, anus; atr, atrium; air 1 , its posterior prolongation, 

 atrp, atriopore ; br, brain ; br.cl, branchial clefts ; brf, brown funnel ; 

 br.sep.i, br.sep.2, branchial lamella? ; br.r.i, br.r.2, branchial rods ; caud.f, 

 caudal fin; cent.c, central canal; cir, cirri; coel, ccelom; dors.f, dorsal fin; 

 dors.f.r, dorsal fin-ray; en coe, cerebral vesicle; e.sp, eye spot; gon, gonad; 

 int, intestine ; Ir, liver ; mth, mouth ; myom, myotomes ; nch, notochord ; 

 nph, nephridia ; olf.p, olfactory pit; or.f.hd, oral hood; ph, pharynx; 

 sk, skeleton of oral hood and cirri (dotted); sp.cd, spinal cord; venl.f, ventral 

 fin; vcnt.J.r, ventral fin-ray; vl, velum; vl.t, velar tentacles. (From the 

 Cambridge Natural History, after Parker and Haswell.) 



Respiratory System. — The pharynx (Fig. 343, ph; Fig. 

 342) is attached dorsally and hangs down into a cavity called 

 the atrium (Figs. 342-343, atr,). The atrium is not the ccelom 



