OCR Text |
Show 1895.] ANATOMY OP NAUTILUS POMPILIUS. 667 cavity is divided by an oblique septum into a large upper division (g.c), the genital division of the ccelom, and a smaller lower pericardium (p.c). The septum separating these is not quite complete, being perforated by three apertures of considerable size. One of these is indicated in the diagram at a. The Genital division of the Ccelom (g.c.) is, as already mentioned, the larger of the two coelomic chambers. It occupies the extreme aboral (dorsal) end of the body, and is lined throughout by a delicate epithelium composed of flattened plate-like cells usually hexagonal in outline, the cell-boundaries, however, being very indistinct;. Each cell contains a rounded nucleus with chromatin network and one or two small nucleoli. Into this division of tbe ccelom project the gizzard, the greater part of the length of the intestine, and the genital gland. It must of course be remembered that all these organs are invested by the ccelomic epithelium, so that it is only in a certain sense that they can be said to be situated within the cavity. The genital gland being merely a specialized part of the wall of the ccelom, it m a y appropriately be shortly described at this point. The Ovary is a flattened ellipsoidal body attached by a mesovarium to the lower (posterior) side of the intestine, and at its oral (ventral) end having a considerable aperture which throws its cavity Eig. 2. Longitudinal section through ovary of a young Nautilus. c.ep, ccelomic epithelium covering outer surface of the ovary; cil.ep, ditto reflected into aperture of ovary; ovfoll, ovarian follicles; ov.l, 2, 3. ova in various stages of development; b.s, blood-sinuses in the wall of the organ. into continuity with that of the surrounding ccelom. The general characters of the ovary are shown in fig. 2, representing a sagittal section through the organ of an immature female. The ovary exists here in almost its simplest possible condition, in the form of a specialized ovigerous area of the ccelomic epithelium roofed over and protected by a simple upgrowth from the ccelomic wall. The outer surface of the organ is covered over by the general epithelium |