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- 



