ELEDONE. 481 
1. The central spherical cell, which contains 
pigment granules, is a uninucleate cell which originates 
in the epidermis and later sinks down into the dermis.. 
The cell wall is a tough elastic membrane, and the 
pigment granules are arranged round the periphery of the 
cell, leaving the central protoplasm clear. 
2. <A girdle of about 18 mesodermal cells becomes 
grouped round the equatorial region of the pigmented 
cell, in a plane parallel to the epidermis. These cells 
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Fic. I1.—Section of the skin. Highly magnified. 
finally become differentiated into triangular muscular 
bands of fibrous tissue, the basal side of the triangle 
adhering to the wall of the vesicle, and the long thin 
apical region being lost amid the surrounding tissue of 
the dermis. <A basal nucleus shows im each fibre. 
3. The elasticity of the vesicle wall opposes the 
contractile tendency of the radial fibres. When the latter 
contract, and the wall relaxes, the vesicle becomes 
stretched out and flattened in a plane parallel to the 
