ALIMENTARY CANAL, ETC., OF AMIURUS CATUS. 391 
to any portion of both cavities, not excepting the inner surfaces of 
the gill arches. 
It falls very distinctly into two coats, of which the outer is the 
epithelial and the deeper corresponds in position to the dermis. The 
latter is formed of connective tissue fibres, elastic fibres, and nerve 
strands, the latter apparently very numerous ; imbedded in this coat 
are a large number of capillaries. Pigment cells are found at the 
boundary of the two coats. The lower is at no point marked off from 
the subjacent stratum which is formed largely of areolar connective 
tissue ; above it gives off both vascular and sensory papillae, which 
rise into pockets of the epithelial coat. The vascular papillae are rare, 
the great majority of the papillae form the base on which the beaker 
organs are situated. These have been already described in the paper 
treating of the skin. The vascular papillae are provided with several 
finely branching capillaries which ascend to their summit. 
Below the base of the beaker organs there is a rich deposit of 
nerve cells easy to be observed, through the deep staining of their 
nuclei with Bismarck brown. The nerve fibrils are at this point 
also observable and can be followed into the epithelial coat. Forked 
pigment cells abound in the summit of the papillae and elsewhere 
along the boundary may form a one-celled layer. 
Most frequently one beaker organ only is to be found on the sum- 
mit of each papilla, but three to five may occur. The epithelial coat 
is clearly marked off from the deeper by columnar cells at its base. 
In itself there is a marked division into regions corresponding in 
position but not in consistency to those of the skin of higher verte- 
brates, denominated horny and mucous layers. Here they pass im- 
perceptibly into one another. 
The superficial layer is formed of cells, generally triangular, each 
provided with a nucleus and a thickened peripheral wall. (Fig. 1). 
They are succeeded below by somewhat horizontally flattened cells 
whose nuclei also bear the appearance of being slightly flattened, and 
are surrounded by but little protoplasm. There are several layers of 
this description. They pass gradually below into cells which are at 
first cubical, thin columnar, their long axis directed perpendicular to 
the surface. While the flattened cells show but little protoplasm, 
these have much and it is finely granular. The columnar shape is 
not a perfect one, being variously angled until the base of the super- 
