578 



BRACHIOPODA. 



The mouth leads into an oesophagus which, passing dorsalwards, 

 opens into the stomach. The stomach receives the ducts of a paired 

 gland called the liver (Fig. 458, o\ and passes into the intestine which 

 is directed ventralwards. The intestine is short, and ends blindly 

 in the Testicardines ; while in the JEcardines it is long and coiled, 

 and opens by an anus into the mantle-cavity. The anus opens on 

 the right side in Lingula and Discina ; in Lingula it is placed 

 between the margins of the mantle. In Crania* the rectum is in 

 the middle line and opens at tne hind end in the middle line into a 

 space between the two valves where the hinge would be. Sometimes 

 the end of the intestine is continued as a cord (Thecidium). 



FIG. 462. Waldheimia australis removed from ijs shell, and with the mantle lobes turned back 

 so as to expose the arms and anterior wall of the body, a ventral, b dorsal lobe of mantle ; 

 c, c gonads ; / peduncle ; g spiral part of the left arm ; h distal limb of the proximal loop ; 

 i tentacles ; j lip, a few tentacles cut away to show it : k position of mouth, which is 

 concealed by the lip ; I occlusor muscles seen through the anterior wall of body ; m left 

 nephridium opening at n. (After Hancock.) . 



The alimentary canal is supported by a median dorsal and ventral 

 mesentery, which partially divides the body-cavity into a right and 

 left half; and by two incomplete transverse septa which pass, as 

 does the dorsal mesentery, from the body-wall to the gut-wall. 

 Of the two latter the anterior is called the gastroparietdl, and the 

 posterior the ilioparietal band, from their relations to the stomach 

 and intestine respectively. 



The nervous system consists of a circumoesophageal ring, upon 



* Joubin, Arch. Zool. Exp. (2) 4. 



