454 CHORDATA. 
carnosus, whilst the fat is concentrated as a layer at the 
base of the dermis, called the panniculus adiposus. This 
layer is enormously developed in most aquatic mammals 
Fig. 320.—SECTION THROUGH THE SKIN OF A MAMMAL. 
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(whales and seals). The skin-glands really belong by origin 
to the stratum mucosum of the epidermis and arise from it 
in the embryo; but as development proceeds they protrude 
downwards into the dermis and become much coiled in 
