ON NAUTILUS AND SOME OTHER ORGANISMS. 175 
that the impression of anastomoses is much more readily 
conveyed by examination with a hand-lens than it is by the 
use of the compound microscope. 
Fic. 20.—Ovary removed from body, and seen from dorsal aspect. On the 
right of the figure the follicular meshes of a submature and a half-mature 
ovum are partially inserted to show difference in size. o. a. Neck of ovarian 
sac, which bears the aperture. o. Ova. gez.a. Genital artery. Only the 
more superficial branches are indicated. 
The germinal tract appears in the centre of the clear polar 
area as a faint whitish spot, and is turned towards the ventral 
aspect of the ovary (Fig. 20). The older ovarian ova are ren- 
dered shapeless by mutual pressure, with, however, a roughly 
oval outline. In this condition an ovum may measure 15:5 
mm. in length, with a breadth of 11°55 mm. When the pres- 
sure is released by slitting open the ovary the ova round up, 
and those which are submature have an average diameter of 
some 10 mm. The yolk is viscous and glutinous, and pos- 
sesses a translucent brownish tinge. ‘The nearly ripe ova 
rupture with the utmost facility. 
From a consideration of the size and relative states of 
maturity of the ova, it might be expected that they are laid 
singly. Every month, from December to September inclusive, 
I have been able to obtain over-ripe males (with spermato- 
phores in the dorsal buccal recess and in the Needhamian 
vesicle) and submature females. Once in July I obtained a 
male with a discharged spermatophore capsule in the buccal 
recess ; in fact, I have found this more than once. 
From these facts, and from the fact which I have previously 
