The systemic heart is white and fleshy, and differs according to the genera in its form, being in the Oc topus semicircular, but in the Loligo and Sepia lobed. Besides giving rise to a large aorta, or principal arte ry, two smaller ones likewise proceed from its cavity. These arteries are furnished at their entrance with valves.
The sexes in the Cephalopoda are distinct, the male and female organs being found on different individuals. There is not, however, any external mark by which they may be distinguished. M. Cuvier found that the males of the Octopus were scarcely a fifth part so nu merous as the females.
The male organs of generation consist of the follow ing parts. The testicle is a large white glandular purse, containing numerous fringed filaments, from which the seminal fluid is secreted. This fluid passes out of the testicle, by a valvular opening, into the vas deferens. This canal is slender, and greatly twisted in its course, and opens into a cavity which has been compared to the seminal vesicle. The walls of this last cavity are strong and muscular, and disposed in ridges. Near the opening at the distal extremity of this sac, is an aperture, leading into an oblong glandular body, re garded as exercising the functions of a prostate gland. Beyond this lies a muscular sac, divided at the top, where it opens by two ducts, but connected at the base. In this sac are numerous white thread-like bodies, ter minated by a filament, but unconnected with the sac. In the interior they consist of a spiral body, connected at each extremity with a glandular substance. When these bodies are put into water, they twist themselves in vari ous directions, and throw out at one of their extremities an opaque fluid. These motions are not excited by placing them in oil or spirit of wine, but they may be exhibited by immersing in water those which have been kept for years in spirits.
These bodies, first observed by Swammerdam, and afterwards by Needham, have been regarded by some as demonstrating the truth of the vermicular theory of generation ; by others, they have been considered as analogous to the pollen of plants—that their tunic is in part soluble in water, and when they are thrown into that fluid, they speedily burst, and spread their impreg nating contents over the eggs of the female. Although this last conjecture is plausible, and countenanced by the circumstance that these vermicular bodies are only found at the season of reproduction, the subject is still involv ed in obscurity. Are these bodies produced in the tes ticle, and only brought to this bag when nearly ready for exclusion ; or, if the product of the bag itself, by what means are they nourished ? The male organs terminate in a cylindrical fleshy body termed the penis. This is hollow within, and ribbed with muscular bands. Near its base it receives one of the ducts of the vermicular sac, continuous with the one from the prostate gland, forming its canal, and toward the apex the other duct. It projects but a short way into the cavity of the great bag, into which it empties its contents. These pass out of the body at the funnel
form opening in the throat.
The female organs of generation consist of an ovarium and oviduct. The ovarium is a glandular sac, to which the ova are attached by footstalks. The opening by which they issue from the ovarium is wide, and the ovi duct (in the Octopus vulgaris and Loligo sagittata,) after continuing a short way simple, divides into two branches, each having its external aperture near the anus. The oviducts are furnished within with muscular bands, and a mucous lining, and encircled with a large glandular zone, destined, probably, to secrete the integuments of the eggs. In the Loligo vulgaris, and the Sepia, the oviduct continues single., Besides these organs, the Loligo vulgaris and sagittata, and the Sepia, have two large oval glandular bodies, divided by transverse par titions, with their excretory ducts terminating at the anus, whose use is unknown.
The eggs, whose peculiar form has been already no ticed, pass out of the funnel, after which they are sup posed to be impregnated by the male, according to the manner of fishes.
The inky fluid now remains to he considered, as the most remarkable of the peculiar secretions of this tribe of animals. The organ in which this fluid is se creted is spongy and glandular. In some species it is contained in a recess of the liver, which has given rise to the opinion that the coloured fluid which it secreted was bile. In other species, however, this gland is de tached from the liver, and either situated in front or beneath that organ. The excretory canal of this gland opens in the rectum, so that the fluid escapes through the funnel. It mixes readily with water, and imparts to it its own peculiar colour. When dried, it is used as a pigment, and is considered as the basis of China ink.
The Cephalopoda are all inhabitants of the sea. They are widely distributed, occurring in the arctic as well as the equatorial seas. In the latter, however, they grow to the largest size. It is reported, that in the In dian Seas, boats have been sunk by these animals affix ing to them their long arms, and that they are dreaded by divers.
In the classification of the animals of this class, many difficulties present themselves, in consequence of the imperfect descriptions of their external characters, given by naturalists. In the following general view we shall endeavour to distribute them into natural groups and genera, without attempting an enumeration of all the species. Such only as are inhabitants of the British seas shall be particularly enumerated.
The Cephalopuda appear to constitute two great divisions, distinguished by the support which is afforded to the abdominal sac. In the first, which may ho termed sepiacea, the sac is strengthened by horny or tes taceous processes, unless where the habits of the animal renders such protection unnecessary. The second divi sion, which may be termed Nautilacea, comprehends those animals furnished with a muttilocular shell. These two divisions constituted in the Linn can system the two genera, Sepia and Nautilus.