5384 TRANSACTIONS LIVERPOOL BIOLOGICAL SGCIETY. 
free surface of the gland, and in cross section appear as 
narrow passages. From these passages secondary canals 
run into the substance of the gland, and end in rounded 
chambers. Into these chambers open minute caeca, 
whose walls consist of the glandular excretory cells of the 
organ. All the above passages are lined with non- 
glandular cells. Blood entering the branchial heart, 
fills the passages excavated in its walls, some of which 
extend into the substance of the adjacent pericardial 
gland. The blood thus comes into contact with the 
excretory cells of the branchial heart appendage, and is 
there deprived of waste matter. 
NERVOUS SYSTEM. 
All Cephalopods have a highly concentrated nervous 
system, which reaches its maximum in Argonauta, 
Octopus and then Hledone ranking next in the series. 
The typical molluscan ganglia are so closely approxi- 
mated, and so intimately connected, as to form a 
peri-oesophageal nerve collar, just behind the buccal mass, 
and between the eyes (Pl. IX, figs. 70 and 76). In 
Eledone, this collar or ‘‘ brain”’ is enclosed in a tubular 
cartilaginous capsule, the anterior and posterior ends of 
which are closed by tough membranes. These are 
pierced for the passage of the oesophagus, posterior 
salivary duct, pharyngeal arteries, &c. (Pl. X, figs. 85a 
and 6, and 82, P.M.). Round the brain, and separating 
it from the cranial walls, is found a kind of gelatinous 
transparent tissue. 
Four pairs of ganglia, the cerebral, the brachial, the 
pedal, and the visceral ganglia, form the brain of Eledone. 
These pairs of ganglia are, however, very intimately 
fused together, and although the supra-oesophageal or 
