190 



ZOOLOGY. 



St Oi cb w, c bf 



Fig. 128 — "Longitadinal section of tiie anterior portion of 

 Lingula. m, mouiti : «, ceaopiiasn-* : .«/, stomach ; q, arm ; cj, 

 cirri ; bf, bracliial fold ; ctf, cartilaginous base of arm ; s. 

 sinns leading to the arm ; cc, cephalic collar or paliial mem- 

 brane. — After Mor^e. 



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

 bordered by two membranous, highly sensitiye 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 ofEshoots of 

 the stomach. 

 The short in- 

 testine ends in 

 a blind sac or 

 in a vent, and 

 is, with the 

 stomach, freely 

 suspended i n 

 theperivisceral 



cavity by delicate membranes springing from the walls of the 

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

 tula, Tereiraholina, Thecidium, Waldheimia, Rhynchonella, 

 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 Lingida 

 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 

 ganglia above, and an 

 infracesophageal 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 infracesophageal ganglia two lateral ventral cords 

 pass backwards, in their tract sending o£E delicate threads. 



',-'9 



Fig. 129. — Transverse section of LingitUL. b. 

 band-< suspending the intestine in the peri^'isce- 

 ral cavity ; i, intestine ; *, segmental organ ; o, 

 ovaries ; l^ liver \ g^ gills ; se, setie.— After 

 Morse. 



