THE CEPHALOPODA. 447 



anus. Hence the alimentary canal has a Vr'enmarked neural 

 flexure (Fig. 125). 



Except in JS^aiitilus^ one or two pairs of salivary ^-lands 

 are present (Fig. 126, I. s'). The liver ^Fig. 126, 1.7^) is al- 

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

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

 erally considered to be pancreatic in fuuction. Very often a 

 large, sometimes spirally wound, caecum is developed from the 

 connnencement 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, nii^ht 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.^ 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 bod^^, 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 which 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 ^ (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, " Eecherches Anatomiqiies et Zoologiques. Premiere Par- 

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

 1845. 



2 On acconnt of the transparency of the tissues in the living Lohgo media, 

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

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

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

 removed. The sacculated afferent veins and the branchial hearts contract 

 about sixtv times a minute. The pulsations of these veins, and of the lu-an- 

 chial hearts, are not synchronous. The branchial veins, and the lamell* of 

 the branchia% also contract rhythmicallv, 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 

 sav 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 cirvlioms 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 brauchio-cardiac ves- 

 sels. 



