1895.] 



ANATOMY or NAITTILUSPOMPILIUS. 



667 



cavity is divided by an oblique septum into a large upper division 

 {(l-c.), tbe genital division of the coelom, 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 Coelom {(i.e.) 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 coelom 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 ivithin the 

 cavity. The genital gland being merely a specialized part of the 

 wall of the coelom, it maj'^ appropriately be shortly described at this 

 point. 



The Ovary is a flattened ellipsoidal body attached by a mesovariiim 

 to the lower (posterior) side of the intestine, and at its oral 

 (ventral) end having a considerable aperture which throws its cavity 



Kg. 2. 



Longitudinal section through ovary of a young Nautilus. 



c.ep, coelomic epithelium covering outer surface of the ovary ; cil.ep, ditto 

 reflected into aperture of ovary; ov.foll, ovarian follicles; ov.\, 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 coelom. 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 coelomic epithelium roofed over 

 and protected by a simple upgrowth from the coelomic wall. The 

 outer surface of the organ is covered over by the general epithelium 



