IV 



ALIMENTARY CANAL COELOM 



123 



the right and left to encircle the front of the pharynx as the 

 peripharyngeal bands. These unite again dorsally to form the 

 epipharyngeal (or hyperpharyngeal) groove which leads backwards, 

 corresponding to the hypopharyngeal groove below (see Fig. 74, A), 

 till the posterior end of the pharynx is reached. 



The remainder of the simple alimentary canal is straight, and 

 is scarcely differentiated into regions. A slight narrowing of the 

 tube behind the pharynx has been called the oesophagus, and a 



FIG. 76. Transverse sec- 

 tion of the ventral 

 part of the pharyn^ 

 of Amphioxus. c, 

 Coelom ; e, endostyle ; 

 gl, endostylar glands ; 

 'ni.h.a, median bran- 

 chial artery ; p.b, 

 primary bar ; sk, en- 

 dostylar and branchial 

 rods and skeletal 

 plates ; t.b, tongue- 

 bar. (After Laukes- 

 ter.) 



sk. 



slight enlargement which follows, the stomach. From this point 

 the intestine tapers backwards to the anus (Fig. 71, p. 116). The 

 ventral edge of the stomach gives off a blind pouch, the hepatic 

 caecum or saccular liver, which runs forwards on the right-hand 

 side of the pharynx (Fig. 74, A, /). This is a digestive gland, is 

 lined with glandular epithelium, and apparently corresponds with 

 the liver of Vertebrata. There are no other digestive glands in 

 connexion with the alimentary canal of Amphioxus. 



Coelom. In the young larva there are at first (as in Balano- 

 glossus) five coelomic spaces, a median anterior " head-cavity," a 

 pair of antero-lateral " collar-cavities," and a pair of more posterior 

 long lateral grooves from which arise, in the later larva, the seg- 

 mented myotomes and ventrally a large coelomic space surrounding 

 the alimentary canal and separating it from the body-wall. In the 

 adult animal, however, the coelom has been so much displaced by 

 the formation of the spacious atrium that in front of the atriopore 

 it can only be recognised as a series of canals and crevices. The 

 relations of coelom to atrium in the region of the intestine are 



