Microscopic Structure of the Integument.
The chromatophores, when examined under the microscope, show, as prevailing colours, black or very deep brown, chocolate-brown, cloudy-purple, full pink, and pale yellow. Each chromatophore appears to have around it a few loose muscular fibres; and at times I have fancied I have detected a loose transparent capsule, with muscular fibres in its walls. In
such cases the chromatophores are well-defined; but often the outline is very ill-defined in one direction. This may, however, be due to the coloured contents having flowed out, leaving a part of the capsule empty, its thin walls being often invisible from their transparency.
The chromatophores appear to be in two distinct layers, as at times one may be seen distinctly overlying another. Thus a deep brown chromatophore may be seen over a yellow one; pink may be seen over yellow; chocolate-brown over pink, and so on.
Above the layer or layers containing the chromatophores is a colourless cuticular layer; below it is a layer containing muscular fibres.
The whole integument is very loosely attached by fine muscular fibres to the substance of the animal; it is loose, but nowhere wrinkled, and is very elastic.