252 PROCEEDINGS OF THE CANADIAN INSTITUTE. 



with which it may be kept in confinement, but chiefly because the 

 entire absence of scales will allow of the application of various histo- 

 logical methods which it is impossible to carry out after decalcifica- 

 tion. With the aid of those methods which have been employed in 

 the study of the moi*e difficult points in the histology of the epider- 

 mis of higher forms, the skin of Amiurus ought to yield more easily 

 than most other Teleosts, results of great interest and probably of 

 general application to the order. 



A 'vertical section of the skin of the head (Fig. 2), indicates the rela- 

 tionship of the various layers of Epidermis and Corium, the elements 

 of which I shall first describe before discussing the peculiarities of 

 the skin in different regions. 



The following different kinds of cells may be detected in the Epi- 

 dermis : — 



a. Superficial Cells. 

 6. Polygonal Cells. 



c. Spindle-shaped Cells. 



d. Palisade Cells. 



e. Mucus-Cells. 



f. Clavate Cells. 



g. Pigment Cells. 



h. Non-epithelial Elements. 



(a) Superficial Cells. — The superficial epidermal cells are distin- 

 guished by their smaller size and flatter form from the underlying 

 polygonal cells. The nucleus, which is always distinct, measures 

 about 4 ;j., the layer of protoplasm outside that rather less than 2 ft, 

 while the whole cell is rarely higher than 8 [i. Ko special cuticular 

 border exists, but all the protoplasm outside the nucleus appears to 

 be denser than the remainder of the cell-body. Although I find it 

 easy enough to detect pore-canals in the cuticule of Petromyzon, I 

 fail to see them in the border of the superficial cells in Amiurus. 

 Rather a striation parallel to the surface is to be detected. It is 

 possible that other methods of preparation than hardening in chromic 

 acid may show the existence of such. The superficial cells are not 

 always flat, but often triangular, with the apex projecting beyond 

 the free surface. This gives a somewhat irregular superficial out- 

 line. Fig. 1. 



(b ) Polygonal Cells. — These hardly differ except in size from the 

 superficial cells. The nuclei are much larger, as much as 8 p, and 



