thoroughly understood. Milne-Edwards, whose opinion is entitled to the highest respect, gives the following explanation of it:—"The skin of these animals is furnished with a number of differently-coloured spots, which alternately appear and disappear, and if a portion is put under a microscope, it may be perceived that these changes depend on the contraction of small vesicles filled with a coloured liquid, which reach from the surface of the skin to a considerable depth. When one of these spots appears, the liquid, corresponding here to the pigment in the other case, is propelled towards the superficial part of the vesicle, and there displays itself; whilst during its disappearance it is forced into the deeper parts by the contraction of this superficial point itself, which then becomes almost invisible."
(Cuttles and Squids.)
- Edinb. New Phil. Journ. XVII. 319.