148 



ZOOLOGY. 



the anterior part of the body of Lingula. The mouth is 

 bordered by two membranous, highly sensitive and movable 

 lips. The stomach is a simple dilatation of the alimentary 

 canal, into which empty the short ducts of the liver, which 



^ is composed of 



,' / / masses of coeca. 



The liver origi- 

 nally arises as 

 two diverticula 

 or offshoots of 

 the stomach. 

 The short in- 

 testine ends in 

 a blind sac or 

 in a vent, and 

 cb m c bf i s with the 



Fig. 98. Longitudinal section of the anterior portion of , , , 



Lingula. m, mouth : a>. oesophagus ; st, stomach : a, arm ; ci, StOmaCn,ireeiy 

 cirri ; bf. brachial Ibid ; eft, cartilaginous base of arm ; <*, -\ -> 



Binus leading to the arm ; cc, cephalic collar or pallial mem- Suspended 1 11 



the peri visceral 



cavity by delicate membranes springing from the walls of the 

 body. (Fig. 99.) In those Brachiopods allied to Terebra- 

 tula, Terebratulina, TJiecidium, Waldheimia, Rhynchonella r 

 etc., the stomach ends in a blind sac, and there is no vent, 

 the rejectamenta escaping from the mouth. In Lingula and 

 Discina there is a vent which terminates anteriorly on the 

 right side. In Lingula 

 the intestine makes a 

 few turns, while in Dis- 

 cina it makes a single 

 turn to the right. 



The nervous system 

 consists of two small 



Fig. 99. -Transverse section of Linffitla. b, 

 bands suspending the intestine in the penvisce- 

 ral cavity : i, intestine ; ., scgmental organ ; o, 

 ovaries ; I, liver ; y, gills ; se, setie. Afler 



Morse. 



ganglia above, and an 



infraoesophageal pair of 



larger ganglia, and there 



are two elongated ganglia behind the arms, from which nerves 



are given off to the dorsal or anterior lobe of the mantle. 



From the infraoesophageal ganglia two lateral ventral cords 



pass backwards, in their tract sending off delicate threads, 



