From the position of the oviduct at the base of the funnel, and the inclination of tbe penis to the same part, from the left side, the latter supposition derives some probability, espe cially with respect to the Sepia and Sepioteu this, in which the penis is of large size, although true intromission is physically impossible in these, as in all other Cephalopods. There may, however, be an imperfect connexion, analogous to that of the Frog, Toad, &c. and it is worthy of remark that the differences in the situation where the coitus is said to take place, in Aristotle's remarkable account, corresponds with the modifications of the locomotive powers in the three genera treated of ; it is only, for example, in the Sepia and Loligo that the indi viduals are provided with posterior fins for swimming forwards.
In the twelfth chapter of the sixth book of the Historia Animalium, where the generation of Fishes is treated of, the Stagyrite ob serves — ' When they (fishes) bring forth, the male following the female sprinkles the ova with his semen :—the same thing happens in the Malakia; for in the genus Sepia!, where the female deposits the ova, the male follows and impregnates them : this possibly happens in like manner to other Malakia, but, hitherto, it has been observed in the Sepim alone.' It reflects, perhaps, little credit on modern Naturalists, that the knowledge of this part of the eco nomy of the Cephalopods should remain in the same unsatisfactory and conjectural state as it was two thousand years ago.
The female organs exhibit four principal types of structure in the Cephalopods.
The ovary is single in all.
In the Nautilus there is one oviduct, and one superadded glandular appendage.
In the Sepia and many others, there is also one oviduct, but there are two separated ni damental glandular laminated organs which open near its extremity.
In the Loligo sagittata there are two distinct oviducts, and two separate nidamental glands.
In the Octopoda there are two distinct ovi ducts, each of which, as in the Ray and Shark, passes through a glandular organ in its course towards the base of the funnel, but there are no detached glands.
In the Nautilus the ovary (a, .fig. 238) is situated, as in the higher Cephalopods, at the posterior part of the visceral sac, in a distinct compartment of the peritoneum ; and the gizzard, which here descends lower down than in the Dibranchiata, is lodged by its side. The ovary is of an oblong compressed form, and in the specimen dissected, measured one inch and a half in length and one inch in breadth. It consists of a simple undivided
hollow sac, with thick and apparently glan dular parietes, rugose on the inner surface, and having an anterior aperture (b) with puck ered margins, directed forwards.
The ovisacs (c, c) are numerous, of an oval form, and attached by one extremity, in a linear series, along the internal surface of the ovarian sac on the dorsal aspect. In the specimen here described they were collapsed, and had evidently recently discharged their ova; the rent orifices by which these had escaped were still patent and conspicuous. The tunics of the ovisacs, as in the Dibranchiata, were glandular, but the internal phew did not present the reticulate disposition characteristic of the corresponding parts in the Sepia, &c. The exterior thin membrane (d) of the ovary is continued forwards to form the oviduct : the thick glandular tunics of this canal com mence by a distinct aperture (e), just above the outlet of the ovary, and continue increasing in thickness to the extremity of the oviduct, where the glandular membrane is disposed in numerous deep and close-set folds : the length of tbe glandular part of the oviduct is one inch ; its termination is at the base of the funnel close to the anus, and immediately behind an accessory glandular apparatus.
This body is analogous to the laminated ovarian gland of the Pectinibranchiate Tes tacea, and, as in them, forms no part of the oviduct; but in the Nautilus it is extended in the transverse direction, and composed of two lateral convex symmetrical masses, resem bling the corresponding separate symmetrical glands in the Decalioda, but which are here united by a third middle transverse series of laminae. All the larninm are deep, pec tinated, and close-set, and are supplied by a large artery. The lateral groups form conspicuous projections on the external sur face of the ventral aspect of the Nautilus, and are covered internally by a layer of thin. tough membrane ; the middle lamina, are exposed.
The female organs of the Dibranchiate Ce phalopods present different structures, as be fore observed, in the Decapodous and Octo= podous tribes. In the former the oviduct or oviducts have laminated glandular termina tions, near to which are placed two detached nidamental glands : in the latter there are al ways two distinct oviducts which pass through laminated glands, but there are no detached superadded glandular organs.