18 



COMPARATIVE ANATOMY 



Fishes. 



The character of the epiderm varies greatly in the different 

 groups (Fig. 12). The striated cuticnlar border (present e.g. in 

 Cyclostomes, Teleosts, and Dipnoans) possibly indicates the 

 former possession of cilia. 1 Cornification of the superficial layer 

 occurs, especially in Teleosts, over those parts of the scales (Fig. 13) 

 which are not overlapped by their fellows. Numerous lymph- 



-JTo 



Co 



FIG. 12. DIAGRAMMATIC TRANSVERSE SECTION ILLUSTRATING THE STRUCTURE OP 



THE SKIN IN FISHES. 



B, B, goblet-cells opening on the surface ; Co, derm ; CS, cuticular margin ; 

 Ep, epiderm ; F, subcutaneous fat ; G, vessels which pass upwards in the 

 vertical connective tissue bundles (8) of the derm ; Ko, goblet-cells ; Ko, 

 granular cells ; W, horizontal connective-tissue bundles. 



cells (leucocytes) are found in the epiderm which have wandered 

 out of the derm, and some of them contain pigment. The derm 

 consists mainly of horizontal and vertical layers of connective 

 tissue, and encloses the other structures already referred to (Figs. 

 12 and 13). 



Various kinds of mucus-secreting cells are formed in the 

 epiderm, and in addition to the relatively larger or smaller goblet 



1 Cilia are occasionally present in very early stages in Teleosts. 



