174 ARTHUR WILLEY. 
suggested, the morphological equivalent of an entire left genital 
apparatus. 
In the female the ramifications of the genital artery pass 
up on to the surface of the individual ova, and form a kind of 
capillary system, the finer branches following, but not always 
confined to, the reticular markings formed by the ridges of the 
follicular membrane which project into the yolk (Figs. 4 
and 5). 
The meshes formed on the surface of the ova by the inter- 
section of the follicular ridges or plications are much wider in 
submature ova than in the less mature, and the ridges would 
presumably be found to flatten out in completely ripe eggs, 
although it has not been my good fortune hitherto to have 
found any such. At the animal pole of the egg the ridges are 
absent, and those which lie at the margin of this area form in- 
complete meshes as described by K 6lliker in the ovarian ova 
of other Cephalopods (Fig. 19). 
Fie. 19.—Fresh ovarian ovum of N. pompilius, to show the reticular 
markings produced by the plications of the follicle. j. a. Clear polar area, in 
the centre of which lies the germinal tract. 
The clear polar area of the ovum has usually a sub- 
triangular shape, and from each of the corners of the 
triangle what may be called a line of weakness occurs in the 
follicular wall, bound on either side by incomplete meshes 
(Fig. 19). 
The arteries which traverse the surface of the ova give off 
minute branches which pass inwards, as it were, into the 
depths of the follicular ridges; and these deep-lying vessels 
anastomose with one another, while the superficial branches 
appear, as a rule, not to form anastomoses. It may be added 
