490 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
edge of the afferent vessel is inserted on the upper end of 
the mantle cartilage, near the insertion of the funnel 
retractor; (6) the depressor muscle of the funnel, 
running out from the funnel to the mantle, near the 
branchial heart (fig. 8, /.D.); and (7) the great lateral 
muscle running out from the cephalopedal mass to the 
mantle (fig. 8, L.M.). 
The epithelium lining the mantle cavity is the 
internal continuation, over the free border of the mantle, 
of the outer skin of this structure, which here becomes 
much thinner and loses its chromatophores, and hence is 
transparent and colourless. However, the epithelium 
covering the dorsal side of the visceral sac bears large 
chromatophores, which show through the mantle during 
life on account of the transparency of this structure. 
Stylets.——On removing the genital gland and the 
posterior portion of the’ alimentary canal, the dorsal 
portion of the mantle is exposed, internally. Two curved 
tracks can be seen, roughly forming a V-shape, posterior 
to the depressors of the funnel (PI. III, fig. 13). By 
dissecting away these muscles, and the great lateral 
muscles, just at their bases, and then removing the inner 
epithelium of the mantle, two colourless, semi-transparent 
rods are exposed (PI. III, fig. 13, C.S.). These are 
chitinous rods, oval in section and tapering at both ends, 
which reach down almost to the posterior end of the 
mantle, and are embedded in its substance (PI. III, 
fig. 16, a and 6). At the point of insertion of the funnel 
depressor the rods are thickest. Pl. III, fig. 16, 
represents a transverse section through the stylet, a stu 
in the mantle. Kach stylet is enclosed in and secreted by 
the walls of an epithelial sac, one cell thick only. These 
cells are columnar, and are rather longer at the two ends 
of the sac than in the central region (fig. 15, Hp.S.). This 
