At other times they darted
tail first, with the rapidity of an arrow, from one side of the
pool to the other, at the same instant discolouring the water with
a dark chestnut-brown ink. These animals also escape detection by a
very extraordinary, chameleon-like power of changing their colour.
They appear to vary their tints according to the nature of the
ground over which they pass: when in deep water, their general
shade was brownish purple, but when placed on the land, or in
shallow water, this dark tint changed into one of a yellowish
green. The colour, examined more carefully, was a French grey, with
numerous minute spots of bright yellow: the former of these varied
in intensity; the latter entirely disappeared and appeared again by
turns. These changes were effected in such a manner that clouds,
varying in tint between a hyacinth red and a chestnut-brown, were
continually passing over the body. (1/4. So named according to
Patrick Symes's nomenclature.) Any part, being subjected to a
slight shock of galvanism, became almost black: a similar effect,
but in a less degree, was produced by scratching the skin with a
needle. These clouds, or blushes as they may be called, are said to
be produced by the alternate expansion and contraction of minute
vesicles containing variously coloured fluids.
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