ANATOMY OF THE TEREBRATULA. 13 



basal portion of the fringed arms uniting the central portions. The swollen margins 

 of the mouth are formed by both muscular fibres and secerning cells : there are no 

 rudiments of a maxillary or dental apparatus. The organic molecules subserving the 

 nutrition of the Bi'achiojjoda are brought by ciliary action within reach of the mouth, are 

 there seized and swallowed. The oesophagus, v, is short, of uniform diameter, has a 

 delicate membranous outer tunic, a muscular coat, and a thicker epithelial lining than that 

 of the rest of the alimentary canal. It inclines slightly forward as it ascends, between 

 the anterior portions of the liver, to terminate in the stomach : it is slightly constricted 

 at its termination, ib. fig. 4 : there is no valvular structure at the cardiac aperture. The 

 stomach, ^, is a simple oblong cavity, swelling out slightly at the cardiac end, where it 

 receives the biliary secretion, continuing thence for some way of the same diameter, which 

 is rather more than half its length ; and gradually contracting to the pylorus. Its tunics 

 consist of an outer membranous, a muscular, and a smooth inner mucous, coat, the 

 epithelium of which is more delicate than in the oesophagus. The whole cavity is bent 

 down at an acute angle with the oesophagus, and the cardiac half is buried in the large 

 granular liver, ib. fig. 1, w. There is no valvular structure at the pylorus: but in some 

 specimens it presented a slight circular constriction. The intestine, ^, is short, straight, 

 and is continued downwards and a little backwards, in a line with the pyloric part of the 

 stomach to the interspace between the attachments of the adductores longi and cardinales 

 to the ventral valve, where the minute vent, -^1;, opens into the pallial cavity, ib. fig. 1. It 

 does not perforate the capsule of the pedicle. The faeces are carried out by the pallial 

 and brachial currents. The intestine is enveloped to within a very short distance of the 

 vent by an extremely delicate venous sinus, pi. 3, fig. 1, 8, the outer wall of which is 

 connected with the plicated auricles, ib. i, i, situated one on each side of the gut, a little 

 above its middle. The muscular tunic of the intestine presents the same uniform 

 thickness as that of the stomach. The muco-epithelial fining membranes are disposed in 

 very delicate transverse plaits, pi. 1, fig. 4, j(. 



The liver, w, is about three times the bulk of the stomach, and forms the most con- 

 spicuous of the chylopoietic viscera, when the abdominal cavity is exposed. It consists of 

 very numerous ramified follicles, the terminal ones of which are of equal size, and their 

 round closed ends give the apparently granular exterior surface to the gland : the intimate 

 structure of the hepatic follicles in Ter.flavescens, agrees with that described in my earlier 

 Memoir, in Ter. psittacea and Ter. chilensis. There is no natural division into lobes ; 

 a slight pressure suffices to displace groups of follicles, which then assume the lobular 

 character. The ducts form the common stems of the manifold ramifications, and they are 

 usually two in number, communicating, each by a distinct aperture, with the cardiac end 

 of the stomach. The liver, as in other Mollusks, is supplied by ramifications of a hepatic 

 artery, the blood thence passing into veins which speedily expand into wide shapeless 

 sinuses, communicating, like the intestinal sinus, with the plicated auricles. 



