242 THE LAMELLIBRANCHIA 
however, the male and female portions of the gonad are not actually 
contiguous, but are united by a short canal (Fig. 218, #, ov), so that the 
spermatozoa have to pass through the ovarian cavity before they are 
— 
fy 
Td 
Fig. 219. 
Lyonsia norvegica, left-side view after remoyal of left pallial lobe and left gill. a, anus; a.a, 
anterior adductor ; a.s, anal siphon ; 6.0, byssal orifice ; 67., branchial nerve ; br.s, branchial 
siphon ; f.o, female orifice; g, gill (direct internal lamina); g’, reflected internal lamina of 
the right gill; g’, outer plate of the gill; l.p, labial palp;; m.o, male orifice ; 0, ovary ; p.a, 
posterior adductor ; p.o, pedal orifice of the mantle ; ¢, testis; v.g, visceral ganglion. 
eliminated. Finally, in the fourth mode, an ovary and a testis com- 
pletely separated from one another exist on either side of the body, 
each having its own proper duct and external orifice. This is the 
case in all the genera forming the order Anatinacea and in Poromya 
among the Septibranchia. In these forms the ovary is dorsal and 
posterior, the testis more anterior 
and ventral (Fig. 219, #0). The 
male and female genital orifices of 
the same side are contiguous ; they 
open on a common papilla in the 
oe 
I> 
6 
fee 
Ss Anatinacea, but the female aper- 
B 4 5 : : 
= ture is outside the visceral commis- 
= sure, and therefore in the normal 
2) oe “,e . 
3 and original position of the Lamelli- 
> . . 
Q branch genital orifice, whereas the 
male aperture is within the visceral 
Ss commissure. In Poromya the male 
fot a and female ducts of each side open 
into a common orifice, external to 
2 the visceral commissure. In all 
» . 
Ky these hermaphrodites the male 
So Va products are the first to ripen. 
Pseudokellya cardijormis, section of a part Accidental cases of hermaphro- 
of the ovary. ce.f, follicular cells ; fol, ovular ditism have been met with in 
follicle ; ov, ovarian egg. A : : , 
dioecious Lamellibranchs (Mytilus, 
Unionidae), and a unisexual individual of the normally hermaphro- 
dite species Pecten gluber has also been described. 
