ALIMENTARY CANAL. 



into a short tube the 

 the test is prolonged 

 as a lining. This 

 passes into a large 

 cavity, the pharynx 

 or branchial sac (Fig. 

 3), the anterior end 

 of which is marked 

 by a row of small 

 hollow tentacles con- 

 taining blood (2). A 

 little further back 

 the pharynx is en- 

 circled by a grooved 

 ridge called the peri- 

 pharyngeal band (3). 

 The portion of the 

 ridge between the 

 tentacular row and 

 the peripharyngeal 

 band is called the 

 prebranchial zone : it 

 is devoid of gill 

 apertures, but bears 

 just anterior to the 

 peripharyngeal band 

 in the dorsal middle 

 line a funnel-shaped 

 ciliated pit, called 

 the dorsal tubercle 

 or ciliated funnel 

 (Fig. 3, 13, Fig. 4, {'). 

 Into this pit, which 

 is lined by ciliated 

 columnar cells, there 

 opens in all Tuni- 

 cata, except the 

 Salpidae (see below, 

 p. 47) and the phoro 

 zooid of Doliolum 



buccal cavity or stomodaeum into which 



FIG. 3. Side view of dona intestinalis. The pharynx and 

 atrial cavity have been opened on the left side (after Shipley 

 and MacBride). 1 mouth; 2 tentacles; 3 peripharyngeal 

 band ; 4 wall of pharynx ; 5 endostyle ; 6 opening from 

 pharynx into oesophagus ; 7 stomach ; 8 intestine showing 

 typhlosole ; 9 rectum ; 10 anus ; 11 atrial aperture ; 12 inner 

 surface of body wall (mantle) showing muscles ; 13 dorsal 

 tubercle 14 subneural gland and ganglion ; 15 cut edge of 

 pharynx wall ; 16 heart in pericardium ; 17 ovary ; 18 pore of 

 vas deferens ; 19 testicular tubes on intestine ; 20 oviduct ; 

 21 anterior boundary of body-cavity (epicardial cavity). 



