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| Fig. 28.—Circulatory and excretory organs of Sepia (from Gegenbaur,after John Hunter). | |
br, Branchiae (ctenidia). c, Ventricle of the heart. a, Anterior artery (aorta). a′, Posterior artery. v, The right and left auricles (enlargements of the efferent branchial veins). v′, Efferent branchial vein on the free face of the gill-plume. v.c, Vena cava. | vi, vc′, Afferent branchial vessels (branches of the vena cava, see fig. 29). vc″, Abdominal veins. x, Branchial hearts and appendages. re, e, Glandular substance of the nephridia developed on the wall of the great veins on their way to the gills. The arrows indicate the direction of the blood-current. |
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| Fig. 29.—Diagram of the nephridial sacs, and the veins which runthrough them, in Sepia officinalis (after Vigelius). Thenephridial sacs are supposed to have their upper walls removed. | |
v.c, Vena cava. r.d.v.c, Right descending branch of the same. r.s.v.c, Left descending branch of the same. v.b.a, Vein from the ink-bag. v.m, Mesenteric vein. v.g, Genital vein. v.a.d, Right abdominal vein. v.a.s, Left abdominal vein. v.p.d, Right pallial vein. v.p.s, Left pallial vein. c.b, Branchial heart. | x, Appendage of the same. c.v, Capsule of the branchial heart. np, External aperture of the right nephridial sac. y, Reno-pericardial orifice placing the left renal sac or nephridium in communication with the viscero-pericardial sac, the course of which below the nephridial sac is indicated by dotted lines. y′, The similar orifice of the right side. a.r, Glandular renal outgrowths. w.k, Viscero-pericardial sac (dotted outline). |
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| Fig.30. | Fig.31. |
| Figs. 30, 31.—Nerve-centres of Octopus. Figure 30 gives aview from the dorsal aspect, figure 31 one from the ventral aspect. | |
buc, The buccal mass. ped, Pedal ganglion. opt, Optic ganglion. cer, Cerebral ganglion. pl, Pleural ganglion. | visc, Visceral ganglion. oes, Oesophagus. f, Foramen in the nerve-mass formed by pedal, pleural and visceral ganglion-pairs, traversed by a blood-vessel. |
| Fig. 32.—Lateral view of the nervous centres and nerves of the right side of Octopus vulgaris (from a drawing by A.G. Bourne). |
| bg, Buccal ganglion. cer, Cerebral ganglion. ped, Pedal ganglion. pl, Pleural, and visc., visceral region of the pleuro-visceral ganglion. gang. stell, The right stellate ganglion of the mantle connected by a nerve to the pleural portion. n.visc, The right visceral nerve. n.olf, Its (probably) olfactory branches. n.br, Its branchial branches. |
Coelom.—The coelom forms a large sac with a constriction between the anterior or pericardial division and the posterior or genital division, and it is produced into lateral diverticula which contain the branchial hearts; but in the Octopoda the pericardial division is suppressed and the genital division communicates by long ducts with sacs containing the appendages of the branchial hearts. The renal sacs communicate with the pericardium by pores near the external renal apertures; in the Octopoda the reno-pericardial openings are in the capsules of the branchial hearts. The genital ducts pass from the genital coelom to the exterior. They are paired in female Oigopsida and Octopoda except Cirrhoteuthidae, but only the left persists in the males of all Dibranchiata, and in the female Myopsida.
In the oviduct is a glandular enlargement, and in addition to this the females are provided with the so-called nidamental glands which are developed on the somatic wall of the pallial cavity, one on each side of the rectum, except in certain Oigopsida (Enoploteuthis, Cranchia, Leachia) and in the Octopoda, in which these organs are absent. The latter fact is related to the habit of the majority of the Octopoda of guarding or “incubating” their eggs, which have little protective covering. In the other cases the eggs are surrounded by a tough gelatinous elastic material secreted by the nidamental glands.
The vas deferens is at first narrow and convoluted, then dilates into a vesicula seminalis at the end of which is a glandular diverticulum called the prostate. By the vesicula and the prostate the spermatophores are formed. These have a structure similar to those of Nautilus, and in the Octopoda may be as much as 50 mm. in length. Beyond the prostate the duct opens into a large terminal reservoir which has been called Needham’s sac, and in which the spermatophores are stored.
Nervous System and Sense-Organs.—The figures (30, 31, 32) representing the nerve-centres of Octopus serve to exhibit the disposition of these parts in the Dibranchiata. The ganglia are more distinctly swollen than in Nautilus. In Octopus an infra-buccal ganglion-pair are present, corresponding to the buccal ganglion-pair of Gastropoda. In Decapoda a supra-buccal ganglion-pair connected with these are also developed. Instead of the numerous radiating pallial nerves of Nautilus, we have in the Dibranchiata on each side (right and left) a large pleural nerve passing from the pleural portion of the pleuro-visceral ganglion to the mantle, where it enlarges to form the stellate ganglion. From each stellate ganglion nerves radiate to supply the powerful muscles of the mantle-skirt. The two stellate ganglia are connected, except in Sepiola, by a transverse supra-oesophageal commissure, which represents the pallial cords united by a commissure above the intestine in Amphineura. The nerves from the visceral portion of the pleuro-visceral ganglion have the same course as in Nautilus, but no osphradial papilla is present. An enteric nervous system is richly developed in the Dibranchiata, connected with the somatic nervous centres through the buccal ganglia, as in the Arthropoda through the stomato-gastric ganglia, and anastomozing with deep branches of the visceral nerves of the viscero-pleural ganglion-pair. It has been especially described by A. Hancock in Ommatostrephes. Upon the stomach it forms a single large and readily detected gastric ganglion.
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| Fig. 33.—Horizontal section of the eye of Sepia (Myopsid).(From Gegenbaur, after Hensen.) | |
KK, Cephalic cartilages (see fig. 8). C, Cornea (closed). L, Lens. ci, Ciliary body. Ri, Internal layer of the retina. Re, External layer of the retina. p, Pigment between these. | o, Optic nerve. go, Optic ganglion. k and k′, Capsular cartilage. ik, Cartilage of the iris. w, White body. ae, Argentine integument. |
| Fig. 34.—Diagrams of sections showing the early stage of development of the eye of Loligo when it is, like the permanent eye of Nautilus and of Patella, an open sac. (From Lankester.) |
| A, First appearance of the eye as a ring-like upgrowth. |
| B, Ingrowth of the ring-like wall so as to form a sac, the primitive optic vesicle of Loligo. |