The tongue may be divided into two por tions ; the one free, and the other fixed, studded with a ntunber of hooklets that can scarcely be estiinated at fewer than from six to eight hundred, the disposition of which at once indicates their office to be to facilitate the propulsion of the food into the cesophagus, as is the case in the Cephalopods and various other Mollusca.
The cesophagus is, for the greater part of its length, surrounded by the two salivary glands, which extend quite into the abdominal cavity, where they are connected to each other, and to the liver by lax cellular mem brane. The stomach is a niere dilation of the cesophagus, and is entirely embedded in the substance or the liver. The latter organ appears, when examined superficially, to be entirely made up of a multitude of Acini, each of which contains within it a cavity that communicates through a wide aperture with the interior of the stomach; and hence it re sults, that, although the exterior of the liver is seemingly composed of large granules, the walls of the stomach are perfbrated all over with openings, leading into blind cavities, so as to have a completely cellular appearance.
The intestine is a simple tube, passing straight from the termination of the stomachal portion of the alimentary canal to the anal oriace, which is situated on the right side of the neck immediately behind the correspond ing fin.
The course of the circulation in the Ptero poda has not been as yet completely made out. In the Clio borealis, the heart enclosed in its pericardium is situated on the right side of the posterior end of the abdominal cavity just at the point where the dorsal and ventral bands of muscle separate to form the wide lateral opening. The pericardium is pointed in front and broad behind : its walls are thin and trans parent, but at the same time very strong. On opening the pericardium, the ventricle of the heart is seen to have the shape of a triangular pyramid with rounded angles, the apex of the pyramid being directed towards the head, whilst its base is turned towards the hind part of the body. From the apex of the heart arises a large vessel, which itnmediately pierces the pericardium, and supplies branches to the liver and to the internal organs of generation ; it then advances forward, and supplies the parts about the neck, more especially the lateral fins, and most probably is ultimately distri buted to the head and its appendages. This
vessel is evidently the aorta.
Generative The reproductive or gans in the Clio borealis occupy a very con siderable portion of the abdominal cavity.
They consist, first, of an Ovary with its oviduct ; secondly of the " bladder ; " and, thirdly, of the testis, upon which the bladder rests.
The ovary (fig. 113. 27, p) is closely con nected with the liver, in conjunction with which it occupies the dorsal region of the abdorninal cavity, its anterior part being filled with the voluminous testicle. The ovary itself is nearly of a hemispherical shape, and is of a pale red colour, its surface having a granular appear ance. When crushed under the microscope, all the granules of which it consists exhibit in their interior a little vesicle, together with a dark spot ; the former being, doubtless, the vesicle of Purkinje, the latter the germinal spot of Wagner.
The• oviduct (q) is tolerably thick, and arises from the middle of the flat surface of the ovary ; it immediately becomes consider ably convoluted, so that it usually forms two loops, and, gradually becoming attenuated, reaches the " bladder "(s), which is situated in immediate contact with the testicle ; but, before joining the latter, it generally swells into a dilatation (r); but this dilatation is not constant ; for sometimes Eschricht found two such enlargements ; whilst in other instances the ovidnct retained the same diameter throughout its entire length : when present, the swelling was found to be solid, and pro bably was produced by an accumulation of ova, coagulated by the action of the spirit in which the specimens had been preserved.
The " bladder " (s) is situated very close to the surface of the testis, and appears to be supported upon a furcate stem, through the intervention of which it is partly in communi cation with the oviduct, and partly with the testicle., This " bladder " is somewhat larger than the accidental swellings of the oviduct alluded to above, but, like them, was found to be solid ; and sometimes the mass was divisible into two flattened halves, a circumstance that would seem to indicate the non-existence of any cavity in the interior.