CEPHALOPODA 



519 



kidney region into two branchial veins, which run to the so-called 

 branchial hearts, special muscular dilatations which pump blood 

 through the capillaries of the ctenidia. The blood which is oxygenated 

 there is sucked out of the ctenidium by the expansion of the auricle. 

 Blood is also returned directly to the branchial heart from the mantle 

 by the abdominal veins (and a smaller pair), and by the unpaired 

 genital and ink sac veins which run first into the right branchial vein. 

 In describing the alimentary system it must first be mentioned that 

 Sepia, as a type of the Decapoda, possesses ten tentacles of which the 

 fourth pair are longer than the others. These two tentacles have a 

 slender stem and a swollen terminal portion to which the suckers are 



p.saLfjL 



ot. ! ped.if. \ 

 fu'.n. bru.g. 



Fig. 381. Vertical section through head of Sepia officinalis showing buccal 

 mass (coarsely stippled) and brain (black) surrounded by the cartilaginous 

 skull (finely stippled). a.sal.gL anterior salivary gland; bra.g. brachial 

 ganglion with brachial nerves coming off from it; ce.g. cerebral ganglion; 

 dig.gl. "liver"; /w.n. nerve to funnel (fu.) coming off from pedal ganglion; 

 y. beaks ; ma.n. mantle nerve ; oe. oesophagus ; ot. otocyst ; ped.g. pedal ganglion ; 

 p.saLd., p.sal.gl. posterior salivary duct and gland; rad. radula; s.buc.g., 

 i.buc.g. superior and inferior buccal ganglia ; vis.g. visceral ganglion. Original. 



confined. Each tentacle can be rapidly extended and attached to the 

 living prey, and with equal rapidity retracted into a pit near the 

 mouth, thus bringing the food into the reach of the other tentacles, 

 which hold it while it is being devoured. Round the mouth are frilled 

 lips and just within it are the characteristic beaks, corresponding to 

 the jaws of the gasteropod, which bite upon each other. The buccal 

 mass is large and contains a well-developed radula and is traversed 

 by the narrow oesophagus. Just behind the buccal mass is the first 

 pair of salivary glands and immediately in front of the digestive gland 

 is the second pair, which produce not a digestive juice but a poison. 

 In Octopus, vfhich lives largely upon crabs, the prey is seized and bitten 

 by the beaks, a drop of the poisonous saliva entering at the same time 

 by the punctures in the carapace and causing almost immediate death. 



