446 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
the epidermis over the gill axis. The coelomoducts are 
flattened sacs, increasing in width from their upper ends 
and widest at a point where the afferent branchial vessel 
leaves them. From this point they narrow rapidly to 
their distal end, which is pointed and lies close to the 
visceral mass. They are simple hollow sacs with 
elandular walls, and the organs are not bent on them- 
selves as in Anodon, nor are there two cavities which differ 
in position and structure. The external openings (fig. 1, 
Ro., rp.) are the renal reproductive apertures by which 
the excrete matters from the pericardial gland and the 
coelomoducts, together with the ova and spermatozoa, pass 
to the exterior. They are prominent vertically-placed 
slits, the long axis of the opening lying almost in the 
same direction as that of the organ itself and situated very 
near the distal end, rather on the free surface of the gland. 
The sht has prominent lips, which are often white in fresh 
or spirit specimens, and thus contrast with the brown 
colour of the organ itself. 
The reno-pericardial opening is very difficult to find, 
and can only be made out with certainty by serial 
sections. The pericardium cannot be injected from the 
renal organs, so that the passage of fluids from the coelo- 
moducts to the pericardium is prevented. It has been 
pointed out that the pericardium is prolonged at each side 
of the digestive gland, and between it and the adductor, 
so as to form two somewhat deep pouches, in which lie 
the distal portions of the two auricles communicating with 
the efferent branchial vessels. In the pallial cavity, very 
close to the digestive gland, there is a nook formed by the 
mantle, visceral mass and digestive gland. Just at this 
point the efferent branchial vessel and the upper end of 
the renal organ lie alongside each other, and the former 
passes into the pericardium; the latter a little distance 
