STRUCTURE OF SEPIA 



459 



sh — i 



is added from the walls of the sac. Between the plates 

 of lime there is gas, and though the structure may give 

 the cuttle some stability, it is probably of more use as a 

 float. 



Internal appearance. — When the mantle flap is cut open 

 and reflected, the two 

 plume-like gills are seen, 

 and the lower end of the 

 siphon. The dark outline 

 of the ink-bag, followed 

 along towards the head, 

 leads our eyes to the end Sr 

 of the food canal. Near 

 this are the external aper- 

 tures of the two kidneys 

 and of the genital duct. 

 On each side of the base 

 of the funnel lies a very 

 large and unmistakable 

 " stellate " ganglion. Re- 

 moving the skin as care- 

 fully as possible over the 

 whole visceral region be- 

 tween the gills, and taking 

 precautions not to burst 

 the ink-sac, we see the 

 median heart, the saccular 

 kidneys, contractile struc- 

 tures or branchial hearts 

 at the base of each gill, 

 and the essential repro- 

 ductive organs near the 

 apex of the visceral mass. 

 Disturbing the arrange- 

 ment of these organs, we 



can follow the food canal, with its stomach, digestive 

 gland, etc. 



Nervous system. — Three pairs of gangUa surround the 

 gullet — cerebral on the dorsal and anterior side, pedal and 

 pleuro-visceral on the ventral and posterior side (Fig. 260), 

 but lying so close together that their boundaries are defined 



Fig. 260.- 

 Sepia.- 



-Diagram of the structure of 

 -Mainly after Pelseneer. 



, Eight short arms around mouth ; l.a., one 

 of the two long arms ; b., beak of the 

 mouth ; e.g., cerebral ganglia, with com- 

 missures to the others; £., eye ; g., guUet ; 

 d.g., digestive gland (the " salivary glands " 

 are not represented) ; St., stomach ; a., 

 anus ; sh., shell-sac with sepiostaire ; k., 

 kidney ; R., reproductive organ ; br.h., 

 branchial heart ; g., a gill ; i.b., ink-bag ; 

 m.c, mantle cavity ; /., funnel. 



