668 MR. J. GEAHAM KERB OX THE [Juue 18, 



of the coelom, having the characters already mentioned, and at 

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

 Traced into the interior ot 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 ovigei-ous 

 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-folUcles of various ages (ov.foll.). 

 In the recesses between the bases of these the Uning epithelium — a 

 thin protoplasmic layer with scattered nuclei and indistinct division 

 into cells — thickens up into syncytial masses of protoplasm contain- 

 ing large round nuclei, each with a large deeply staining nucleolus, 

 around \A'hich the protoplasm tends to segregate off" more or less 

 distinctly. The primitive o\ um develops within such a heap, the 

 nucleus increasing in size and assuming more and more the cha- 

 racter of a " germinal vesicle," and the protoplasm first becoming 

 more distinctly aggregated round the nucleus and marked off from 

 the surrounding protoplasm and then increasing rapidly in size. As 

 the ovum increases in size the substance of the ovarian wall grows 

 up round it to form the follicle, while the sjTicytium accompanying 

 the ovum apparently gives rise to the lining-cells of the follicle. 

 The latter are pear-shaped structures borne on stalks, which are 

 usually simple, but occasionally branch, thus showing a tendency 

 towards the condition in Arr/onauta, where they are much branched 

 and tree-Uke. Externally the follicle is covered by a very thin 

 epithelium, which distally becomes continuous with the lining 

 layer of " follicle-cells" — a layer of thick columnar cells immediately 

 surrounding the egg. In the young follicle this layer runs con- 

 centrically with the outer surface of the epithelium, but as the egg 

 increases in bulk an increase in the surface of this apparently 

 nutritive organ becomes necessary and the follicle-epitheUum grows 

 inwards as a series of anastomosing folds. On this account the older 

 eggs when removed from the follicle show on their surface a net- 

 work of deep fissures formed by the follicular epithelial ingrowths. 

 In the oldest fercale specimen accessible, unfortunately too 

 macerated to make out many details, the eggs had reached a large 

 size, over 10 mm. in length, and their substance was already enor- 

 mously yolk-laden, the protoplasm being practically restricted to a 

 small cap on the end of the egg next the follicular opening. 

 Imbedded in this was the large nucleus with densely staining 

 nucleolus. The presence of a definite opening in at least the older 

 follicles and the position of the egg-nucleus close to this, suggest 

 the possibility of fertilization in Nautilus being internal ; and the 

 great size of the eggs and their yolk-laden character point to the 

 segmentation being meroblastic as in other Cephalopoda. 



The wall of the ovary, as of other important organs, is loose and 

 spongy, traversed by extensive blood-sinuses (6.s,). Prolongations 



