THE PHARYNGOBRANCni. 



105 



straight intestine, ending in the anal aperture, wbich is situ- 

 ated at tlie root of the tail at a httle to the left of the me- 

 dian line (Fig. 28, A, c). The mucous membrane of the in- 

 testine is ciliated. 



An aperture called the abdominal pore (Fig. 28, A, e), 

 placed in front of the anus, leads into a relatively spacious 

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

 pharynx, to near the oral aperture. The water which is con- 

 stantly propelled into the pharynx by its cilia, and those of 

 the tentacles, is driven out through the branchial clefts, and 

 makes its exit by the abdominal pore. 



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

 ntestine, the apex of which is turned forward. 



""iG. 29. — Anterior end of the body of AmpMovn^. — C%, notochord; My, myelon, t>r spinpj 

 chord ; «, position of olfactory (?) sac; &, optic nerve ; c, fifth (?) pau-; f7, fepinal nerves ; 

 e, representatives of neural spines, or fin-i-ays ; y, gr, oral skeleton. The lighter and 

 darker 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 retams the tubular condition w^hich it possesses 

 in the earliest embryonic stage only, in other T^ertehrata. 

 The blood brought back from the body and from the ali- 



