In the West Indies, South Africa, South America, and New Zealand occur examples of a peculiar genus of animals, which has been named Peripatus, and has been at different times referred to the Errant Annelides, the Leeches, the Tapeworms, or the Myriapoda. The species of Peripatus are terrestrial in their habits, living in moist earth, in decayed wood, or under stones, active by night only, and completely worm-like in form. The cylindrical body (fig. 173) is annu-lated, and provided with numerous pairs of ambulatory feet, which are jointed, and terminated by one or two hooked claws (fig. 173, C and D), sometimes with a bunch of setae. The animal walks like a caterpillar, by means of its feet, and rolls up like a Millepede when alarmed. The mouth is furnished with one or two pairs of horny hooked jaws. The respiratory organs, as recently shown by Moseley, are in the form of tracheae, which open externally by numerous diffused apertures, and rarely branch. From the researches of Moseley, the sexes would appear to be distinct, though the animal is stated to be hermaphrodite by Grube and Hutton. The ventral nerve-cords are widely divergent.
The systematic position of Peripatus must in the meanwhile be regarded as doubtful, the animal presenting a type of structure intermediate between the Errant Annelides and the Myriapoda. The presence of tracheae, however, renders it impossible to place Peripatus amongst the Annelida, and the affinities of the genus appear to be closer with the Myria-pods than with any other group; though the wide separation of the ventral nerve-cords, along with other points, removes Peripatus to a considerable distance from the normal forms of the Myriapoda. If Peripatus should ultimately be retained in the Myriapoda, it would be as well, for the sake of uniformity, to change Grube's name of Onychophora to that of Onychopoda.
Fig. 172. - Pauropus Huxleyi, viewed from above, and enlarged fifty diameters. (After Sir John Lubbock.)
Fig. 173. - A, Peripatus Edwardsii, magnified two diameters. B, Head, viewed from below, enlarged five times. C and D, A single foot, viewed from above and sideways, enlarged. (After Grube.)