SKA-FISHERIES LABORATORY. 449 
cavity of the duct. The opening to the exterior is lined 
for a short distance with non-glandular, more compact, 
normal ciliated epithelium, the lips being formed by a 
slight development of cushions of connective tissue. 
In addition to the organ of Bojanus, excretion 1s 
carried on by the pericardial glands. These are confined 
to the auricles, to which they give a very distinct brown 
tint. The auricle has the wall thrown into numerous 
pockets, which increase its surface. It is formed of a 
single layer of epithelial cells (fig. 49, Awr.), somewhat 
flattened, and with prominent nuclei. Internal to this, 
there is a considerable amount of loose connective tissue 
with scattered muscle fibres, and amidst these lie the cells 
(Aur. ex.) which by reason of their contents give the 
brown colour to the surface. ‘hey are large, and very 
similar in form to those described in the connective tissue 
sheath of the alimentary canal, except that more proto- 
plasm appears to be present; oval in shape, with the 
nucleus near one end, and the rest of the cell almost filled 
by a mass of some refractive siructureless substance 
surrounded by a thin cortex of protoplasm. Usually, the 
large mass of cell contents shows a granular central 
portion of an olive green tint, and surrounding this a 
part which stains, hke connective tissue and chitin, a 
light blue with Methyl-blue-eosin. 
The two forms of excretory organs already described 
seem to perform difterent work. If indigo carmine 
solution is injected into the animal, it will be eliminated 
by the cells of the organs of Bojanus; whilst if ammonium 
carminate is injected, it is taken up by the pericardial 
excretory cells. 
The latter cells, which have been described as placed 
chiefly on the auricles, occur also in the mantle, fhe 
visceral mass and around the intestine. 
