II 



INTEGUMENT 



INTEGUMENT OF HEPTANCHUS MACULATUS 



One of the most characteristic structures observed in a study of the external 

 form is the integument, in which is located the pigment pattern and from 

 which project the shagreen denticles. The two layers of the integument of a 

 young Heptanchus are shown in figure 26. The epidermis (e.) is relatively 

 thin and the dermis or corium {cr.) is considerably thicker. 



The epidermis when examined in detail shows superimposed strata of cells, 

 the innermost layer of which, the basal or ger- 

 minative layer {gr.), is of a columnar nature; 

 while the outlying strata in which the cells are 

 horizontal may be designated as the superficial 

 layers of the epidermis. Between these two ex- 

 tremes are numerous intermediate cells which 

 are irregularly stratified. These cells arise in 

 development from the basal layer and pass out- 

 ward toward the surface, becoming more flat- 

 tened as they move outward. 



At practically any level of the epidermis 

 from the deep basal layer outward to the sur- 

 face may be found large beaker or goblet cells 

 {fj.c. ) of a glandular nature. Each of these cells 

 arises as a modified cell divided off from a basal 

 layer cell and comes to be essentially a large sac 

 with the nucleus located near its base. 



The dermis or corium (cr.) is composed of 

 two more or less well defined layers in Heptan- 

 chus. The first or more superficial of these is 

 made up of a dense mass of irregularly ar- 

 ranged cells; the second or deeper layer is com- 

 posed of sparser cells which have protruding from them longer or shorter 

 processes, which interlace into a network of supporting tissue. 



In the upper layer of the corium and between it and the epidermis are lo- 

 cated the pigment masses which are the causes of the color pattern. In the 

 adult the pigment cells are black or greyish and are distributed more or less 

 evenly over the back and sides, giving to the upper areas their drab hue. Over 

 the drab background are scattered the irregular blotches of black which are 

 produced by more deeply lying pigment. In the patches the cells are packed 

 so closely together that it is impossible to pick them out individually. Pig- 

 ment is absent from the integument on the ventral side, which is of a whitish, 

 metallic color. 



Fig. 26. Section through the 

 buccal integument, Heptanchus 

 maeulatus. 



h.m., basal membrane; cr., 

 corium or dermis; e., epidermis ; 

 g.c, goblet or gland cell; gr., 

 basal or germinative layer. 



[23] 



