. Elements of Comparative Anatomy. 340 COMPAEATIVE ANATOMY. Cephalopoda. In these latter the gills arise in just the same way— between the mantle and the foot (Fig. 171, B hr)—as they do per- manently in many Grastropoda. When, however, the mantle is developed they sink downwards, and are then placed in a mantle- cavity, which, as compared with the Gastropoda, appears to open on the hinder surface. The gills are arranged symmetrically in all of. Fig. 178. Mantle-cavity and funnel of Sepia officinalis. The mantle-cavity lias been opened by an incision along the middle line. In it is seen the vi
. Elements of Comparative Anatomy. 340 COMPAEATIVE ANATOMY. Cephalopoda. In these latter the gills arise in just the same way— between the mantle and the foot (Fig. 171, B hr)—as they do per- manently in many Grastropoda. When, however, the mantle is developed they sink downwards, and are then placed in a mantle- cavity, which, as compared with the Gastropoda, appears to open on the hinder surface. The gills are arranged symmetrically in all of. Fig. 178. Mantle-cavity and funnel of Sepia officinalis. The mantle-cavity lias been opened by an incision along the middle line. In it is seen the visceral sac projecting, while posteriorly to it two muscular branches are given off (m) to the funnel and head. Br Branchicc. r b?'Branchial vein, v 6/Its bulbous enlargement. t Ink-bag. r Orifice of the excretory organ, opened on the right side, and displaying at R the venous appendage, g Genital papilla, a Anus. /Funnel, oi^ened by an in- cision along the middle Une. i Tongue-shaped organ, c Depression for the process at the edge of the mantle (pallial hinge) c'. C Head. P Fins. them; there are two pairs in the Nautilus, but only one in all the other extant Cephalopoda. As a rule, each gill is pyramidal in form, with the apex directed towards the side, and its base towards the middle line (Fig. 178, Br). It either consists of closely-approximated lamellae, which gradually increase in number at the tip (Nautilus, and most Loliginidfe), or of several much-coiled dermal folds, which arise between the two branchial vessels which pass to the edge of the mantle (Octopoda).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Gegenbaur, C. (Carl). London : Macmillan
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