External Features.
The anterior part of the body may be called the head, though it is not sharply marked off from the rest of the body (Fig. 1).
Fig. 1.—Peripatus capensis, drawn from life. Life size. (After Sedgwick.)
Fig. 2.—Ventral view of hind-end of P. Novae-Zealandiae. (After Sedgwick.) g, Generative opening; a, anus.
Fig. 3.—Ventral view of the head of P. capensis. (After Sedgwick.) ant, Antennae; or.p, oral papillae; F.1, first leg; T, tongue.
The head carries three pairs of appendages, a pair of simple eyes, and a ventrally placed mouth. The body is elongated and vermiform; it bears a number of paired appendages, each terminating in a pair of claws, and all exactly alike. The number varies in the different species. The anus is always at the posterior end of the body, and the generative opening is on the ventral surface just in front of the anus; it may be between the legs of the last pair (Fig. 2), or it may be behind them. There is in most species a thin median white line extending the whole length of the dorsal surface of the body, on each side of which the skin pigment is darker than elsewhere. The colour varies considerably in the different species, and even in different individuals of the same species. The ventral surface is nearly always flesh-coloured, while the dorsal surface has a darker colour. In the South African species the colour of the dorsal surface varies from a dark green graduating to a bluish gray, to a brown varying to a red orange. The colour of the Australasian species varies in like manner, while that of the Neotropical species (S. American and W. Indian) is less variable. The skin is thrown into a number of transverse ridges, along which wart-like papillae are placed. The papillae, which are found everywhere, are specially developed on the dorsal surface, less so on the ventral. Each papilla carries at its extremity a well-marked spine.
The appendages of the head are the antennae, the jaws and the oral papillae.
The antennae, which are prolongations of the dorso-lateral parts of the head, are ringed, and taper slightly till near their termination, where they are slightly enlarged. The rings bear a number of spines, and the free end of the antennae is covered by a cap of spiniferous tissue like that of the rings.