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, on the present occasion, to give some results at which I have arrived respecting the anatomy and physiology of the Dibranchiate Cephalopods; whose structure I have been engaged investigating for some time past. My observations will be confined almost entirely, to the so-called water system and to the blood system; and on these points I shall speak as concisely as possible, reserving for some future opportunity detailed accounts of them, when I hope to be able to lay before those interested in such subjects a memoir treating on the general anatomy of this order of the Cephalopoda.

First, then, with regard to the so-called water system. In the Octopodidæ this consists of five chambers; namely, two large chambers, containing the venæ cavæ; two small lateral ones, which open into the above, and which communicate by long slender tubes with the fifth, the posterior or "genital chamber," which always contains the special genital organ, the ovary or testis, according to the sex.

The two first-mentioned chambers lie along each side of the median line, separated by a membranous partition, and immediately within the abdominal wall. The liver lies in front of, and above, the ovary or testis behind them. Each opens into the branchial chamber by a nipple-shaped orifice placed near to the root of the gill. These two chambers contain the two venæ cavæ, with their glandular appendages. The convoluted or upper portion of the intestine, and a limited portion of the branchial hearts, also project into these cavities. Over all these organs the membranous wall of the chamber is reflected; but on the glandular appendages of the venæ cavæ if is scarcely, if at all, demonstrable. I shall uniformly designate these the "renal chambers," as they always contain the venæ cavæ with their glandular appendages, which latter undoubtedly perform, in whole or in part, the function of a kidney, as is now generally admitted.

Besides the external nipple-shaped openings already specified, there are other two orifices leading into these chambers. Those orifices are situated in the dorsal wall of the chamber, close to the base of the nipple-shaped orifices; and establish a communication between the renal chambers and two small, elongated cavities placed between the wall of the former and the lateral walls of the abdomen. These orifices are also somewhat nipple-formed, with the lips opening outwardly, or into the renal chambers, and are placed at the anterior extremity of the small chambers; the other extremity, which is some- what enlarged, abuts upon the branchial heart, and encloses within it the so-called "fleshy appendage" attached to that blood-propelling organ. The interior of these small chambers is longitudinally and irregularly laminated, with the surface of a glandular appearance, and