118 



THE ANATOMY OF VEETEBEATED ANIMALS. 



cavity, which is continued forwards, on each side of the 

 pharynx, to near the oi-al aperture. The water which is 

 constantly propelled into the pharynx hy its cilia, and those 

 of the tentacles, is driven out throiigh the branchial clefts, 

 and makes its exit by the abdominal pore. 



The liver (Fig. 28, A, d) is a saccular diverticulum of the 

 intestine, the apex of which is turned forwards. 



FifT. 29. 



Fig. 2'.t.— Anterior end of the body of Amphioxvs :- Ch, notochord ; 

 -"^y, myelon, or spinal chord ; a, position of olfactory (?) sac ; 0, optic 

 nerve ; c, fifth (?) pair ; d, spinal nerves; e, representatives of neu- 

 ral spines, or fin-rays ; /, ff, oral skeleton. The lighter and darljer 

 shading represents the muscular segments and their interspaces. 



The existence of distinct kidneys is doubtful; and the re- 

 productive organs are simply quadrate glandular masses, 

 attached in a row, on each side of the walls of the visceral 

 cavity, into which, when ripe, they pour their contents. 



The heart retains the tubular condition which it possesses 



