2 Oe 
194. TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
groove. The rest. of the epidermis of the viscero-pedal 
mass consists of short columnar, non-ciliated cells, with a 
continuous thick cuticle. 
As on the internal surface of the mantle edge, this 
ciliated portion of the foot is also an area provided with 
unicellular mucus-secreting glands. These form a con- 
tinuous dense layer beneath the ciliated epidermis, and are 
imbedded in the loose muscular sheath of this part of the 
foot. Each of these glands (figs. 21 and 22, Pl. IV.) consists 
of either a single cell or a group of from 2 to 6 cells aggre- 
gated together. Single-celled glands are uncommon, and 
are only found near the posterior limit of the glandular 
area. Towards the tip of the foot they are more complex; 
the largest groups measure about 0°3 mm., the stalks 
being about half that length. ‘Such a complex gland con- 
sists of a group of cells forming a bulb with a long stalk. 
The limits of the separate cells are not always clearly 
distinguishable. The cell bodies consist of a reticulum, 
some of the bars of which are rather coarse; these are, 
however, continuous with a very fine meshwork, which 
apparently makes up the cell substance. This reticulum 
is continuous from cell to cell. Nuclei are not evident, 
but in every cell there is a nodal point at the intersection of 
several of the coarser bars of the reticulum; reticulum 
and nodal points, and the finest ground substance, stain an 
intense blue with haematoxylin. The stalk is non-tubular, 
has the same structure as the bulb, and breaks up at its 
free end into a small number of branches which penetrate 
between the epidermal cells and form little knobs among 
the cilia on the surface of the foot. The structure and 
staining reaction of these bodies, coupled with the habit 
which the very young cockle has of pulling itself along a 
smooth surface by causing the tip of its foot to adhere to 
