CLASS OF THE CEPHALOPODA. 



509 



found concealed in the mantle, under a particular cavity (Fig. 

 533), whose walls dilate and contract alternately, and whose 

 interior communicates with the exterior by two openings, 

 The one (o) in the form of a fissure serving for the entrance 

 of the water; the other, prolonged into a tube or funnel (t}, 

 serving for the escape of the water and of the residue of the 



a vc as b 



vv av a cs vv 



Fig. 534 Organs of Respiration and Circulation in the Cuttle Fish.* 



food. Each gill (b) has the shape of an elongated pyramid, 

 and is composed of a great number of membranous lamellae, 

 placed transversely, and fixed on either side of the median 



* c, the aortic heart, the superior extremity of which is continuous with 

 the superior aorta (as), distributing the blood to the head, &c. ; b, the 

 branches of this vessel ; a, the inferior aorta, presenting a bulb at its origin, 

 and soon dividing into two branches (vv) ; vc, vena cava, whose walls are 

 covered by the spongy bodies (e,?) ; vv, veins of the viscera proceeding to 

 open into the two branches of the vena cava ; cp, venous sinuses or branchial 

 hearts; s, enlargement of the base of the branchial arteries; br, gills, ab, 

 branchial artery ; vb, branchial vein ; bu, bulb of the branchial veins situated 

 near the termination of the vessels in the heart, and constituting the 

 auricles. 



