190 



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 co3ca. 

 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 

 is, with the 



ft a 



Fig. 128 Longitudinal section of the anterior portion of 



Lingula. m, mouth ; CK. cesophairu^ : *?/, stomach ; a, arm ; ci, Stomach,freely 

 cirri ; bf, brachial ibid ; cb, cartilaginous base of arm ; $, 11* 



pinus leading to the arm; cc, cephalic collar or pallial mem- Suspended. 111 



theperivisceral 



cavity by delicate membranes springing from the walls of the 

 body. (Fig. 129.) In those Brachiopods allied to Terebra- 

 tula, Terebratulina, Thecidium, Waldheimia, Rhynconella, 

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

 the rejectamenta escaping from the mouth. In Lingula and 

 Distina 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. 129. Transverse section of Lingula. b, 

 bands suspending the intestine in the perivisce- 

 ral cavity ; i, intestine ; ., segment al organ ; 0, 

 ovaries ; I, liver ; ft, gills ; se, setie. After 

 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, 



