542 CEPHALOPODA. 



on each side ; these sinuses are relatively larger which separate the intestinal sac from that of 



in the Sepia than the Octopus. In both species the pyloric appendage and that of the stomach; 



the branchial vein resumes its ordinary dimen- winds round the latter, and passes, by a proper 



sions before terminating in the ventricle; but in opening, to the right of the cardia through the 



the Cuttlefish the sinus is placed closer to the muscular septum, and into the cavity behind 



ventricle. the liver, and ascends on the right side of the 



The systemic ventricle (o) is situated in the dilated oesophagus to the cartilaginous cranium, 



mesial plane between the bifurcation of the Here, after distributing branches to the sur- 



vena cava above, and the ovary or testis below, rounding parts, it bifurcates and completely 



In the Octopus and Eledone it presents a glo- encircles the gullet; and from this vascular 



bular form, rather extended tranversely, and ring, which is strikingly analogous to the bran- 



with the branchial sinus entering at its superior chial arches in Vertebrata, the head and all its 



and lateral aspects. In the Loligo and the complex radiating appendages derive their nu- 



Onychoteuthis (jig. 227) it is lozenge-shaped, triment. 



with the long axis in the axis of the body; RESPIRATORY ORGANS. The branchiae pre- 

 giving off the two aortas (c, d) by the anterior sent the same general form and structure in both 

 and posterior angles, and receiving the bran- orders of Cephalopods, but differ, as before ob- 

 chial veins ("a, ,3 at the lateral angles. In the served, in number, and also in their mode of 

 Sepia, (o, jig. 225,) Sepioteuthis, and Rossia, attachment to the mantle. They are always 

 the systemic ventricle is a fusiform body, bent entirely concealed and protected by the mantle, 

 upon itself at right angles. About one-half on which is extended forwards so as to form a 

 the right side lies in the axis of the body, the peculiar chamber for them anterior to the other 

 remainder extends transversely to the left side ; viscera, and into which the rectum and gene- 

 the extremity of this part receives the left bran- rative organs open. It is interesting to perceive 

 chial vein, the other extremity gives off the an- the respiratory cavity retaining, in the highest 

 terior aorta (q, jig, 225). The bulb of the organized Mollusks, that relation with the anal 

 posterior and generally the larger aorta (p, jig. extremity of the digestive canal which we trace 

 225) is continued from the middle of the through the whole of this type of animal con- 

 transverse portion ; the right Abranchial vein formation, and which forms so well-marked a 

 enters the middle of the right side of the Ion- line of distinction between the Molluscous and 

 gitudinal portion of the ventricle. Vertebrate divisions of the animal kingdom. 



In all the Dibranchiata the parietes of the In the Nautilus the four branchiae are at- 

 systemic heart, though thin, are firmer and more tached by their bases only to the inner surface of 

 muscular than those of the branchial hearts; and the mantle; but in the Dibranchiates a thin 

 its cavity is generally about three times greater fibrous membrane connects the fleshy stem of 

 than that of either of the others : its inner each gill to the contiguous surface of the man- 

 surface shows the regular interlacement and tie. In the Nautilus the branchiae are subject 

 decussation of the columnae carnese, none to contortions from the want of this support ; 

 of which, however, project into the cavity, and in the specimen which we dissected, we 

 The termination of each branchial vein is found the gills on one side closely bent upon 

 defended by a pair of membranous semi- themselves, with their apices turned down; this 

 lunar valves (b, Jig. 227). The origin of the circumstance does not probably impede a cir- 

 lesser aorta (p), arising from the anterior part culation which flows with an equable and con- 

 of the ventricle, is defended by a single valve tinuous current through the gill ; but where the 

 (e,fg. 227); that of the great aorta, (q',jig. blood is driven in jerks by the contractions of 

 226,) which, though posterior in its origin, is de- a powerful ventricle, a necessity then exists for 

 stined to supply the head and anterior parts of the pro vision of a free channel for the passage of 

 the body, is generally provided with a mus- the fluid ; and accordingly we find that the 

 cular bulb, as in the Nautilus. In the Octopus obstruction of the branchial artery by the 

 it is defended, according to Cuvier, by two bending of the fleshy stem of the gill is obvia- 

 semilunar valves; but in the Calamary and ted by the simple but effectual means above 

 Onychoteuthis by a single valve (f t jig. 227). described, viz. the superaddition of a connect- 

 In the Octopus there is also a third small ing membrane, which always preserves the gill 

 artery (r, jig. 225) given off directly from the in a straight position. 



ventricle, which is distributed to the generative In both orders of Cephalopoda the branchiae 

 organs, and presents considerable periodical present an elongated pyramidal figure, with their 

 variations of size in relation to the functions apices directed forwards : they are compressed 

 of those parts. In the same genus the small from before backwards in the Nautilus (n, m, 

 aorta, which arises from the anterior part of Jig. 224), and from side to side in the Cuttle-fish 

 the ventricle, first gives off two long and slender (i, k, Jig. 225) and most other Dibranchiates. 

 branches ( s, s, Jig. 226), which are distributed They are composed of a number of triangular 

 to the venous follicles, whose arterial vascularity vascular laminae extendingtransversely from each 

 we have before mentioned. The trunk then di- side of a central fleshy stem (h,jig. 225), having 

 vides into two arteries, of which the largest (t) an alternate disposition : each lamina is corn- 

 ascends in front of the vena cava to be distri- posed of smaller transverse laminae, which are 

 buted to the mantle; the other supplies the again similarly subdivided ; the entire gill thus 

 folded intestine and surrounding peritoneum, exhibiting the structure called by botanists <tri- 

 The large aorta first passes backwards and to pinnate,' by which an extensive surface is afford- 

 the right between the layers of peritoneum ed for the minute division of the branchial vessels. 



