SEPIA. 281 



The blood vascular system is highly developed. The 



heart lies below the intestine (if the intestine were bent 



back into a straight line it would be in the 



usual dorsal position) and consists of a ventricle 



and two auricles. The auricles receive blood 



from the ctenidia by the eflerent branchials and drive it into 



the ventricle. From the ventricle it passes forwards and 



backwards by anterior and posterior aortce. 



The veins are largely sinuses but are rather more 

 definite than in other molluscs. A main vein, the vena 

 cava, runs along the mid-ventral line from the head to the 

 level of the anus, where it divides into two afferent branchials 

 going out to the ctenidia. At the base of the ctenidia each 

 afferent branchial' swells into a brafichial heart or contractile 

 bulb, which also receives an abdominal vein from the hind 

 region and on contraction drives the blood up the ctenidium. 

 The heart of the cuttle, like that of our preceding types, is 

 therefore systemic, but in addition there is a pair of special 

 respiratory or branchial hearts. 



The brain is a large mass lying over the oesophagus and 

 protected by the cranial cartilage. It supplies nerves to the 

 eyes and the otocysts. Connections run round 

 the oesophagus to a ventral nerve-mass which, 

 as in the snail, consists of several ganglia. The pedal and 

 pleurovisceral may be distinguished. Nerves from the pedal 

 supply the ten tentacles and the siphon. For this and 

 other reasons derived from embryology we are led to regard 

 the tentacles and the siphon as together representing the foot 

 of the other Mollusca. We have seen that the intestine and 

 excretory pores have moved forwards along the mid-ventral 

 line and the foot, divided into tentacles, has moved forwards, 

 like the appendages of the lobster, to surround the mouth. 

 As in the lobster, the ventral surface of the body is bent 

 upwards anteriorly. There are two large stellate ganglia 

 on the lateral walls of the mantle-cavity, connected by pallial 

 nerves to the pleurovisceral ganglia. 



There is a pair of large tubular kidneys which open 



internally into the pericardium and externally to the 



Excretory ^^^erior as described. They envelop the 



afferent branchial and abdominal veins, and 



their walls consist of thickened excretory cells. 



