186 



J. GRAHAM KERR. 



organ is covered over by the general epithelium of the coelom, 

 having the characters already mentioned, and at the opening at 

 the oral (ventral) end of the ovary this is inflected into its 

 interior so as to line this likewise. The cavity of the ovary is 



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. 1, 2, 3, 

 ova in various stages of development; b.s, blood-sinuses in the wall of 

 the organ. 



thus merely an incompletely shut-off portion of the coelom. 

 Traced into the interior of the ovary, the epithelium about its 

 opening assumes a columnar form and bears long cilia (cil. ep.). 

 Along its roof the cells become shorter and eventually cubical. 

 About two-thirds of the way from the mouth of the cavity the 

 ovigerous region is reached, and this occupies the remainder of 

 the roof and nearly the whole of the floor of the ovary. The 

 ovigerous region of the cavity is thickly beset with egg-follicles 

 of various ages (ov. foil.). In the recesses between the bases of 

 these the lining epithelium — a thin protoplasmic layer with 

 scattered nuclei and indistinct division into cells — thickens up 

 into syncytial masses of protoplasm containing large round 

 nuclei, each with a large deeply staining nucleolus, around 

 which the protoplasm tends to segregate off more or less 

 distinctly. The primitive ovum develops within such a heap, 

 the nucleus increasing in size and assuming more and moi-e the 



