368 ORGANS OF DIGESTION. 



(B. b.). The narrow short oesophagus leads to an elongated 

 stomach (B. c.} covered by the lobes of the dark green- 

 coloured liver, and the intestine (B. d. e.) passing backwards 

 between the lobes of the ovary (B. k. k.) and forming one 

 convolution, returns to the upper part of the shell, or of the 

 abdominal cavity, where it penetrates the ventricle (B. i.) of 

 the heart (B. h.i.). Escaping from the cavity of the heart, 

 the intestine ascends, as usual, over the great adductor muscle 

 (B. /. s. m.) of the valves, and terminates by a simple anal 

 opening (B. e.) near the respiratory vent. On opening the 

 mouth (120. D. a. a.), the oesophagus (D. b.), and the 

 stomach (D. c.), we perceive the limits of the lobed lips 

 (D. a.) the muscular fibres and transverse rugse of the oesopha- 

 gus (D. b.), and the numerous apertures (D. d. d.) of the 

 stomach, by which the bile is poured into that cavity to mix 

 with the food before it is sent into the small intestine (D. e.) 

 The intestine (B. d. e.) is not perceptibly perforated in its 

 parietes in the part which is contained within the ventricle 

 (B. i.) in this or other conchifera. The blood from the 

 palleal (B. f.) and the branchial (B. g.) veins enters the two 

 lateral portions of the auricle (B. h.), by which it is sent into 

 the ventricle (B. i.), and from this it is distributed by an 

 anterior and posterior aorta for the nourishment of all parts of 

 the body. So that the digestive organs of the testaceous 

 acephala exhibit a higher development than is presented by 

 the naked species, chiefly in the large and often complicated 

 buccal appendices, the gastric stiliform cartilage, the con- 

 stant presence and great development of the liver and the 

 length of the alimentary canal, and it differs from that of the 

 tunicated species, by its passing through the muscular ven- 

 tricle of the heart, by the greater number of its convolutions, 

 and by the greater extent of its course, being enveloped in the 

 mass of the liver. 



XVI. Gasteropoda. The numerous and diversified class of 

 gasteropods presents a more complicated and more varied 

 digestive apparatus than the acephalous mollusca, which 

 accords with the greater variety observed in their food and 

 habits ; for most of the terrestrial pulmonated species feed on 

 the highly organized vegetables of the land, while the naked 

 marine gasteropods, as the doris, eolis, scyllaa and tritonia, 

 subsist on the lowest fuci of the sea, and most of the pro- 



