INTEGUMENT 



17 



epidermic layer in many fishes (e.g. Cyclostomi, Teleostei, and 

 Dipnoi), and, as will be mentioned presently, in Amphibian larvae, 

 indicates the former possession of cilia (Figs 10 and 11). 

 ' Goblet-cells (unicellular glands) are very abundant in the many 

 layered epidermis of Cyclostomes (especially Myxinoids) and 

 osseous Fishes, and are extremely numerous in Protopterus. 



Protopterus buries itself in the mud during the dry season, and its integu- 

 ment, which, besides the numerous goblet-cells, also contains simple multi- 

 cellular glandsli]\.e those of the Amphibia, gives rise to a varnish-like secretion 

 as well as to a hardened capsule or " coccoon," by means of which the animal 



FIG. 10. DIAGRAMMATIC TRANSVERSE SECTION ILLUSTRATING THE STRUCTURE OF 

 THE SKIN IN FISHES. 



Ep, epidermis ; Co, derma ; F, subcutaneous fat ; OS, cuticular margin ; Ko, 

 goblet-cells ; B, B, goblet-cells opening on the surface ; Ko, granular slime- 

 secreting cells present in Petromyzon and Malopterurus; G, vessels which 

 pass upwards in the vertical connective -tissue bundles of the derma ; W, hori- 

 zontal connective- tissue bundles. 



is protected during its torpid period. In all Fishes which possess slime- 

 secreting cells in the integument, it is probable that the secretion serves to 

 protect the outer skin from the action of the water. 



Midticelhdar glands are not commonly present in the integu- 



c 



