Attached to the base of each branchial heart, and depending into the viscero-pericardial sac, is an appendage, the pericardial gland of Grobben, or so-called fleshy appendage. It corresponds in Nautilus to vascular appendages of the branchial arteries, which project into the viscero-pericardial sac, and resemble the vascular tufts which project from the same vessels into the nephridial sacs both of Nautilus and Dibranchiata. The blood contains amoeboid corpuscles and haemocyanin.

1 The fossil beaks of Tetrabratuhiata are known as Rhyncholites.

2 This buccal membrane is lobed; it sometimes bears suckers, and is supplied by nerves derived from the brachial nerves, and therefore from the pedal ganglia. Viailleton regards it as representing a series of arms nearly aborted with well-developed interbrachial membranes. See C. R. 100, 1885.

The viscero-pericardial sac (pericardium, secondary coelome) is of very large size in Nautilus and Decapoda. It includes the heart, the roots of the branchial arteries, the branchial hearts of Decapoda, stomach, and, except in the male Sepia, the genital organs as well. The testis in Sepia is contained in an almost closed diverticulum of it. It communicates in Nautilus with the branchial cavity by a right and left aperture close to the openings of the posterior pair of nephridial sacs; in Decapoda with the nephridial sacs themselves, by a wide slit-like opening in Oegopsidae, e. g. Ommastrephes, by a small pore in Myopsidae, e.g. Sepia. The corresponding sac is reduced in Octopoda to a small space which incloses the pericardial gland, and opens into the nephridial sac of its side by a pore; to a narrow canal connecting each space to the genital sac; and to the genital sac itself. This series of spaces is sometimes spoken of as the water-canal system. It is absent in Argonauta Argo and Ocythoe tuberculata (= Tremoctopus Carenae).

The respiratory organs consist in Tetrabranchiata, i.e. in Nautilus, of two, in Dibranchiata of a single pair, of ctenidia, free in the former, attached by one aspect in the latter. The branchial artery runs up the attached or in Nautilus the homologous side, the vein on the free surface. A mass of cells, with intervening blood-lacunae, is situated in the line of attachment in Dibranchiata. It is possibly a blood-making gland. The surfaces of the ctenidia are disposed in a series of respiratory folds transverse to the ctenidial axis. The folds differ in shape in Octopoda and Decapoda.

There are four nephridial sacs in Nautilus, two in Dibranchiata, each opening by its own aperture, which in Dibranchiata is often produced into a papilla. The four sacs of Nautilus and the two of Octopoda are independent. In Decapoda they are either connected to a median sac lying between them (Sepia), or fused into one as in the majority, e. g. Loligo. The walls of these sacs are covered by a more or less flattened epithelium, except at the spot where they are in contact with the branchial arteries. The latter here give off a number of caecal and branched venous appendages. The nephridial epithelium coating these vascular tufts is columnar and longitudinally striated, its surface covered with a slimy secretion, in which reddish-coloured crystals, also occurring loose in the sac, are commonly found, as well as greenish-coloured spheres. Crystals and spheres alike appear to be excretory products1. Vascular tufts of a similar character are given off by the branchial arteries of Nautilus into the viscero-pericardial sac. The pericardial gland appended to the branchial hearts (supra) in Dibranchiata appears to be a structure of excretory character.

It is a somewhat conical body, which contains a number of caeca communicating by one (Sepia) or several (Eledone) slits with the viscero-pericardial sac, and lined by an epithelium continuous with that of the sac. At the bases of the caeca the epithelium becomes glandular.

The sexes are separate. The single testis and ovary are formed from the walls of that part of the viscero-pericardial sac or secondary coelome in which they lie, and from which the ciliated ducts are prolonged to the exterior. The left duct is rudimentary in both sexes in Nautilus; there are two ducts in the male Eledone moschata (Oetopoda), and the female of Ommastrephes (Decapoda), and of Oetopoda, except Cirrhoteuthis, whereas in other instances there is but one duct, that of the left side. The vas deferens has a widened glandular section, and bears an accessory gland, and near its termination a large sac, Needham's sac, in which the spermatophores are contained. It ends in a papilla, which may be of great extent, in Oetopoda. The spermatophores are cylindrical bodies of some length and complicated structure, containing not only sperm but an exploding substance as well. The oviduct in Oetopoda has as a rule a dilated portion (present but unilateral in Nautilus) with walls produced into glandular leaflets, forming an albumen gland. In Decapoda a similar gland opens into the end of the oviduct. The oviduct, like the vas deferens, opens between the anus and nephridial aperture.

Nautilus possesses a nidamental gland, situated on the mantle, the Decapoda a pair of such glands, in both cases composed of lamellae. A third gland, composed of coiled tubes, is present in most female Decapoda.

With the exception of a few Dibranchiata (e. g. Ommastrephes), a remarkable change affects one of the arms in the male. It is enlarged either at its apex or base, and the suckers of the enlarged portion obliterated.

1 Solger found that sulph-indigotate of soda ( = indigo carmine) when injected under the skin of an Eledone moschata made its appearance in this excretory epithelium as well as in solution in the cavities of the nephridia. Cf. Z. A. iv. 1881. Injection of the same substance into the blood of Ma?nmalia is followed by its excretion in the kidney and the liver.

It is then said to be hectocotylised. In Argonauta Argo, Ocythoe tuberculata (= Parasira catenulata), Tremoctopus violaceus, and T. quoyanus, this arm or Hectocotylus is set free, and reproduced after each act of sexual congress. It developes within a sac, which then bursts, disclosing a large arm with peculiar suckers, and a terminal saccule. The latter bursts in its turn, setting free a 'NeedhamV filament. The modified arm is in all cases charged with spermatophores, which appear to gain access to it by an aperture on its aboral surface. When it is detached it is carried away by the female in the branchial cavity1. The ova are either inclosed, each in a special capsule, which is attached to some foreign object; or carried in the shell (Argonauta); or a number are imbedded in a mass of gelatinous material, fixed (Loligo) or floating. Segmentation is partial, the protoplasm collecting in a terminal disc. The yolk is not inclosed in the alimentary canal, but is lodged in what appears to be a median part of the foot, in the head, neck, and mantle.

Cilia have been observed on the blastoderm.