There are in some fishes, like the John Dory, curious eye-like dark spots, which we cannot refer to a structural origin, though a better acquaintance with the class might reveal such significance.
The Amphibia have not been well studied by us, and we must leave them with the remark that they seem to bear out the view of structural decoration, as is seen in our English newts. Some are, however, modified out of all easy recognition.
Reptiles. Among the reptiles, the snakes, [Fig. 4], may be selected for illustration. Snakes are practically little more than elongated backbones, and are peculiar from the absence of limbs. The colouring matter does not reside so much in the scales as in the skin beneath, so that the sloughs do not illustrate the decoration. Hence, we might expect to find here a direct effect of morphological emphasis.
The ornamentation of snakes is very similar throughout the class, both in water and land snakes; as may be seen by Sir W. Fayrer's work on Venomous Snakes. This ornamentation is of a vertebral pattern, placed along the dorsal surface, with cross lines, which may represent ribs.
Where the ribs are wanting, as in the neck, the pattern changes, and we get merely longitudinal markings.
In the Python, [Fig. 4], there are, near the central line, numerous round spots, which apparently emphasize the neural processes. There are diagonal markings on some species which illustrate the development of colour-spots already alluded to.
This snake-pattern is very singular and striking. The markings are fewer in number than the vertebræ, yet their true vertebral character is most obvious.
In Snakes, again, we find the dorsal region is darker than the ventral.
In the Lizards there are patches of colour placed axially, while each patch covers a number of scales.