CEPHALOPODA 



595 



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

 by the narrow oesophagus. Just within 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, which 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 im- 

 mediate death. This is true of Sepia also which lives upon prawns and 

 shrimps. The food is bitten into pieces by the jaws — sometimes of 

 considerable size — and passed down the oesophagus (which though 

 narrow is capable of considerable distension) to the muscular, non- 



8.6 mc.(/ 



p.sal.gl. ce.g 



oe. 



digjjl ->y;- 



ma.n 



VI 



is.g. ot. ! ped.g. \ 



fu'.n- bra.g. yw. 



Fig. 406. 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./z. nerve to funnel {fu.) coming off from pedal ganglion; 

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

 lion ;/).5a/.£/., p.sal.gl. posterior salivary duct and gland; rad. radula; s.buc.g., 

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



glandular stomach. Here it is mixed with the secretion from the 

 digestive gland and the digested food passes to the spiral coecum. 

 This contains an elaborate ciliary mechanism which removes solid 

 particles from the coecum, leaving only liquid products of digestion 

 to be absorbed there. The digestive gland consists of a solid bilobed 

 gland ("liver") and a more diffuse and spongy part ("pancreas"). 

 Both are enzyme-producing, but the "pancreas" (which in Sepia is 

 suspended in the kidney sac) is al^o partly excretory. The single 

 duct opens into the coecum, but a groove guides its secretion into 

 the stomach. The "liver" is the principal "storage organ" for food 

 reserves ; it seems probable that these only reach the 'gland from the 

 blood-stream, and that food is all absorbed in the alimentary canal, 



