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Show 1895.] ANATOMY OP NAUTILUS POMPILIUS. 669 of these pass up the stalks of the follicles, and form a specially developed layer immediately underlying the follicle-epithelium-a condition to be correlated with the provision of an abundant blood-supply to satisfy the needs of the glandular epithelium. The Testis is, in its main morphological features, quite similar to the ovary; in other words, it is an invaginated area of the lining of the coelom. Only in the testis great increase in the area of the germinal epithelium has been brought about by the involuted portion of coelomic epithelium, instead of remaining a simple sac, becoming divided up into a system of delicate branched tubes. In an apparently adult specimen, tbe testis was a large brownish organ of roughly triangular shape, its rounded apex directed upwards and towards the right side. Its apical portion was in close contact with the body-wall, while its basal part was separated from the body-wall by the pericardium. The testis is slung up by a strong ligamentous band about 1 cm. broad to the tunic of the gizzard, by a similar but broader band which is attached along a sagittal line to the body-wall (the root of the siphuncle being about the middle of its line of attachment), and finally along its anterior face by a thin peritoneal fold to the loop of the intestine. Further, at its lower end the epithelium covering the outer surface of the testis is continued into that covering the pericardial septum and heart. Near the inferior angle of the organ is its aperture-a slit about 2 m m . in length, bounded by two flat, much projecting lips, which, lying closely opposed to one another, project into a deep recess covered by a crescentic flap, the internal opening of the vas deferens. Thus, though the cavities of the testis and of the vas deferens open quite independently into the coelom, they are at least during sexual maturity functionally continuous with one another. In a section through the testis of a young individual, the aperture of the organ is seen to lead into a vestibule into which open several straight ducts. Each of these, traced inwards, divides up into numerous tubules which end blindly and are aggregated into distinct lobes and lobules. Vestibule and tubes are lined by epithelium continuous with that of the general coelom. The wall of the organ is traversed by a sponge-work of blood-sinuses. Between the lobules these are greatly developed, their separation walls being reduced to fine connective tissue-threads serving to bind the lobes together. Into the substance of the lobules also pass continuations of the sinuses. Regarding the character of the epithelium in different parts of the tubes, the state of the specimens does not allow m e to say anything. The Pericardium or inferior chamber of the ccelom is considerably smaller than that already described. It immediately underlies the " postero-dorsal" body-wall throughout its half next the mantle-flap, and its cavity is conveniently exposed by reflection of its external wall. It is then seen to be quadrangular in outline, rather broader than long (68 m m . x 54 m m . in one specimen). From its inner (anterior) wall, in a curved row parallel to the |