THE CEPHALOPODA. 447 



anus. Hence the alimentary canal has a well-marked neural 

 flexure (Fig. 125). 



Except in Nautilus, one or two pairs of salivary glands 

 are present (Fig. 126, I. s'). The liver (Fig. 126, I. h) is al- 

 ways large ; and there are two hepatic ducts (Fig. 126, 1, dh), 

 beset for a greater or less extent with glandular follicles, gen- 

 erally considered to be pancreatic in function. Very often a 

 large, sometimes spirally wound, caecum is developed from the 

 commencement of the intestine ; into this the hepatic ducts 

 open. 



The heart (Fig. 127, c) is placed upon the posterior face 

 of the body on the haemal side of the intestine, and receives 

 the blood by branchio-cardiac vessels, which correspond in 

 number with the gills, and, as they are contractile, might be 

 regarded as auricles. The gills themselves have no cilia, and 

 are, in some cases, if not always, contractile. The arteries 

 end in an extensively-developed capillary system, but the 

 venous channels retain to a greater or less extent the char- 

 acter of sinuses. 1 The venous blood, on its way back to the 

 heart, is gathered into a large, longitudinal sinus — the vena 

 cava — which lies on the posterior face of the body, close to 

 the anterior wall of the branchial chamber, and divides into as 

 many afferent branchial vessels as there are gills. Each of 

 these vessels traverses a chamber w T hich communicates di- 

 rectly with the mantle-cavity, and the wall of the vessel which 

 comes into contact with the water in this chamber is saccu- 

 lated and glandular 2 (Fig. 127, re). Each chamber, in fact, 

 represents a renal organ. The pericardium, and the sacs in 

 which the testes and ovaria are lodged, may communicate 



1 Milne-Edwards, " Recherches Anatomiques et Zoologiques. Premiere Par- 

 tie." " Observations et Experiences sur la Circulation chez les Mollusques," 

 1845. 



2 On account of the transparency of the tissues in the living Loligo media, 

 this species affords an easy opportunity of observing the rhythmical contrac- 

 tions of the branchiae, and their afferent and efferent vessels. For this pur- 

 pose the mantle should be laid open, and the nidimental glands carefully 

 removed. The sacculated afferent veins and the branchial hearts contract 

 about sixty times a minute. The pulsations of these veins, and of the bran- 

 chial hearts, are not synchronous. The branchial veins, and the lamella? of 

 the branchiae, also contract rhythmically, but I could observe no contraction in 

 the branchial arteries. The portion of the branchial vein which lies between 

 the base of the gill and the systemic ventricle is very short, and it is hard to 

 say whether it contracts independently or not. Mechanical irritation causes 

 contraction both of the afferent branchial veins and of the branchial hearts. 



In the living Eledone cirrhosus I have observed regular rhythmical con- 

 tractions of the vena cava itself as well as of its divisions, the sacculated affe- 

 rent branchial veins, of the branchial hearts, and of the branchio-cardiac ves- 

 sels. 



