RP 
53 
are lowest in the scale (Spondylus) there is a direet discharge of 
genital products into the cavity of the kidney. In the higher de- 
veloped forms there is a tendency for the insertion of the genital 
duct into the kidney to travel outwards: in the next stage the ducts 
open separately to the exterior, but on the same papilla (Pinna, 
Mytilus): finally there are separate and more distant exterior open- 
ings for the genital and exeretory apparatus. 
The communication between the excretory organs and the peri- 
cardium is retained in a much larger number of Mollusks and Pro- 
neomenia seems to prove that a still more primitive stage which 
preceded the direct communication between genital gland and kidney 
on the one hand and between kidney and pericardium on the other, 
is that in which the cavity of the pericardium (body-cavity) is the 
point of meeting between the deferent ducts of the genital gland and 
the excretory ducts of the renal organ. 
Finally I must insist upon one fact which is not without signi- 
fieance, viz. that in both my specimens of Proneomenia there is 
not the slightest trace of any calcareous penis, penis-sheath, vas 
deferens or any of the corresponding structures described by TuLı- 
BERG and Kor£y and DANIELSSEN, structures which I also 
found both in the sections of Proff. v. GrAFF and Ray LANKES- 
TER. As I have no reason to believe the sexes to be separate in Pro- 
neomenia and have described the aspect of the hermaphrodite gland, 
its histologieal constituents and its contents I must look upon this 
as a rather fundamental difference between Neomenia and Proneo- 
menia, & difference in which Chaetoderma perhaps participates on 
the side of the latter genus. The „looped mucus glands’” (see 
above p. 37) with common duct, also described by Kor£n and 
DANIELSSEN correspond to our organs AA’ RR. These searchers 
appear not to have noticed any communication with the pericar- 
dium. 
