DIGESTIVE SYSTEM 



753 



no notochord and no neural tube. Practically none of the structures 

 characteristic of the dorsal side of Amphioxus are present. 



FISHES 



The mouth opens directly into the capacious pharynx, which is per- 

 forated by five gill-clefts and the paired spiracles. A short oesophagus 

 of large caliber leads into a U-shaped stomach (Fig. 438), which in turn 



Fig. 438. 



A female dogfish in which the abdominal and pericardial cavities have been 

 opened from the ventral side, and the viscera somewhat displaced. The pericardium 

 has been opened slightly to the left of the middle line, and the right lobe of the 

 liver has been cut away. 



ab. p., Abdominal pores ; 6., bile duct ; c., cardiac limb of stomach ; c.ar., caudal 



