THE CEPHALOCORDA 185 



into the sub-intestinal vein, and so the circle is completed. It 



C. 



Fig. 45 



A, Anterior portion of the nerve cord of Amphioxus, after Schneider. cnl, ctfi, 

 first and second pairs of " cranial " nerves ; ar} t dorsal roots of the first pair, and 

 dr^ t dorsal roots of the fourth pair of spinal nerves ; z/r 1 , z>r*, the correspond- 

 ing ventral roots ; e, eyespot. B. Diagram illustrating the circulation in 

 Amphioxus. af. afferent branchial vessel with enlarged bulbil ; ao, dorsal 

 aorta ; br.a, branchial aorta ; ef, efferent branchial vessel ; hep, hepatic 

 diverticulum ; hv, hepatic vein ; nch, notochord ; pb, primary bar ; tb, tongue- 

 bar ; si.v, sub-intestinal vein. C. Section through a primary, and D, section 

 through a tongue-bar. a.ep, atrial epithelium ; b.ep, branchial epithelium ; 

 cce, ccelom ; j, skeletal rod ; zA, internal, z/ 2 , external, and V s , coelomic 

 blood-vessels. E. Section through the endostyle. br.a, branchial aorta ; 

 c, median cilia of endostyle ; cce, subendostylar coelom ; j, skeletal rods. 

 (C, D, and E after Benham.) 



should be noted that in Amphioxus the blood runs forwards in 



