File:Image from page 298 of "Animal biology" (1940).jpg

English: Title: Animal biology

Identifier: animalbiology1940wolc Year: 1940 (1940s) Authors: Wolcott, Robert Henry, 1868-1934; University of Nebraska (Lincoln campus). Dept. of Zoology Subjects: Zoology; Biology Publisher: New York ; London : McGraw-Hill Book Company, Inc. Contributing Library: MBLWHOI Library Digitizing Sponsor: MBLWHOI Library

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Text Appearing Before Image: CHAPTER XLIV ONYCHOPHORA AND MYRIAPODA Onychophora (onikSf ora; G., onychos, claw, and phoros, bearing) is a class of the phylum Arthropoda which in a natural classification should come first, since it is not only the simplest of the arthropods but has a pronounced resemblance to the annelids, suggesting a derivation of arthropods from annelid-like ancestors. 307. Onychophora.—The typical genus of this class is Peripatus, which contains numerous species reported from widely separated local- ities in Australia, New Zealand, Tasmania, New Britain, the Malay Archipelago, South America, Mexico, West Indies, and Africa. It is a wormlike form with a soft skin covered by papillae, each papilla bearing

Text Appearing After Image: Fig. 176.—Peripatus; an individual shown entangling a cockroach in sticky threads formed by a secretion ejected from papillae on its head. {From Pearse, "General Zoology," by the courtesy of Henry Holt & ComjMny.) a spine. Metamerism is not marked externally, but there is a series of short, fleshy legs in pairs, each ending in two claws. There is also an oral papilla on each side of the mouth and a pair of simple eyes. Peripatus shows a number of annelid-like characteristics. The skin is thin and not so heavily chitinized as in the arthropods generally, there are paired and segmentally arranged nephridia in all but the first two metameres, and there is a marked resemblance to the annelids in the general arrangement of internal organs. In other ways, however, it seems to be truly an arthropod, since it has tracheae (Sec. 313), appendages modified to form jaws, and body cavities which are hemocoelic. It differs, how- ever, both from other arthropods and from annelids in having a single pair of jaws, in the texture of the skin, and in the simplicity of the metamerism. The species of Onychophora live in crevices in rocks, under stones, and in the dark recesses of rotting logs, where they move slowly about from place to place, always avoiding the light. When disturbed a very 273

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