342 MOLLUSCA 



its secretion forms the basis of the well-known color, sepia. Xaiililus 

 and some Octopoda ha\-e no ink sac. 



lust beliind the luiccal mass are the closely united chief ganglia of 

 the nervous system (lig. 357) surrounding tlie cvsophagus. A single 



Fig. 356. — Anatomy of Oclof>iis vulgaris. T. basis of tentacles; K, head; .1/, 

 mantle spUt venlrally, opening visceral sac; liver ami ncphridia removed, vena' cava- 

 \vith appendages folded back; n, anus; ao, aorla; i;», eye; a.', vena cava with ncphridial 

 appendage; d, intestine; <", pericardial sac with nc]ihridial opening; go, oplic ganglion; 

 /;, svstemic heart; /, crop (a'sophagcal apiicndagel; k, gills; kli. branchial heart; kii, 

 cephalic cartilage; /, liver and /', gall duct (jiosilion of liver indicated by dotted line); 

 m, stomach; 0, ovary; oil, o\iducl; /;, pedal ganglion; r, passage connecting with ovary; 

 r', mouth of pericardial sac in nephriilial sac; .!, a'sophagus with dorsal salivary gland; 

 sf}, ventral salivar\' glands; si, stellate ganglion; ,?\', sympathetic ganglion; /, ink sac; 

 V, visceral ganglion; vk, auricle of systemic heart; .v, s[iiral blind sac. 



dorsal mass represents the cerebral ganglia; connected mth tliis liy 

 broad commissures, the pedal and \isceral (\iscero-pleuro-]iarietal) 

 ganglia lie close together ventrally. Witli these parts are associated 



