borne on a fine suspensory membrane. Across the space between them stretch still smaller plume-like lamellæ (id., fig. 2), each with a small capillary. These sub-lamellæ look like repetitions of the entire gill; but, on microscopic examination, it is seen that they consist of a capillary with a very thin membrane thrown into transverse folds (fig. 3) on each side. The renal organ (fig. 1 g) is well-developed on the branches of the vena cava. Two long lobes extend over the heart, which they almost hide; and each of these lobes has a well-marked opening, which communicates with its branch of the vena cava. Thus, if air be blown into one of the openings, it inflates its branch of the vena cava, and also the branchial heart into which that branch opens. Reproductive Organs. Male (pl. vi.).—The male organs consist of a testis, vas deferens, “prostate” gland, duct of the “prostate,” receptacle of spermatophores and penis. The testis (fig. 1 g) lies at the ab-oral end of the body, is large, irregularly oval in outline, and flattened. Its lower outline is concave, its upper convex. It is encased in a thin membrane attached on its anterior surface and uniting it below with the inner anterior surface of the mantle. The vas deferens communicates with the capsule of the testis towards the upper end. Its commencement seems rather to be lost in the membrane than to have a well-marked opening. It is short but slender, and does not present the convolutions noticed in all descriptions of the male organs of Cephalopods that I have seen. The vas deferens opens into a long, cylindrical vesicula seminalis, which leads to the “prostate” gland. The walls of the vesicula present well-marked transverse plicæ. Except that it narrows at either end, it is of about the same thickness throughout. It contains spermatozoa, which appear, when examined with the ¼-in. objective, to be simple straight rods. Though the walls of the vesicula appear to be thick and white, they are in reality thin and transparent, the white colour being caused by the spermatozoa. The plicæ may possibly be due to only partial distention. The “prostate” gland (fig. 1 d; fig. 2) is a delicate tube, presenting marked convolutions, and having the appearance, when viewed on the posterior aspect, of a spiral coil. At the point where the vesicula seminalis enters it is dilated (3); then there is a strong convolution; then a slightly expanding tubular portion (2), which leads to a sac-like portion (1). Near the point where the vesicula enters is a small cœcal dilatation (4); and a similar dilatation is produced from the saccular portion from which the duct springs.