Some of those zoologists who look to Peripatus, or a similar worm-like form, as representing the direct ancestors of the Hexapoda have laid stress on a larva like the caterpillar of a moth or saw-fly as representing a primitive stage.
In Peripatus they occur in every somite of the body.
(From Lankester, loc. cit., after Packard.) with all air-breathing Arthropoda except Peripatus, possesses these tubules, which are often called Malpighian tubes.
(From Korschelt and Heider, after Leuckart.) Peripatus, Diplopoda, Hexapoda and Chilopoda.
Very usually (but not in the Onychophora = Peripatus) all the parapodia are plated with chitin secreted by the epidermis, and divided into a series of joints - giving the " arthropodous " or hinged character.
In Peripatus the prostomium of the Chaetopod-like ancestor is atrophied, but it is possible that two processes on the front of the head (FP) represent in the embryo the dwindled prostomial tentacles.
Ence of one, and only one, prosthoII, Coelom of the second mere in Peripatus, of which the somite which carries the " protocerebrum," P, is the neuromandibles (hence deu mere, whilst the deuterocerebrum, terognathous).
The Chaetopod in Peripatus is not P, Protocerebrum or fore clearly ascertained, nor is its fate most cerebral mass be indicated by the study of the emlonging to the first bryonic head of other Arthropods so somite.
Probably it is fused with the D, Deuterocerebrum, consist protocerebrum, and may also be ing of ganglion cells be concerned in the history of the very longing to the second or peculiar paired eyes of Peripatus, mandibular somite.
The appendages of the first prosthomere are not present as tentacles, as in Peripatus and Diplopods, but are possibly represented by the eyes or possibly altogether aborted.
In Peripatus no such adhesion or fusion occurs.
It is not true that all the biting processes of the Arthropod limb are thus produced - for instance, the jaws of Peripatus are formed by the axis or corm itself, whilst the poisonjaws of Chilopods, as also their maxillae, appear to be formed rather by the apex or terminal region of the ramus of the limb; but the opposing jaws (= hemignaths) of Crustacea, Arachnida and Hexapoda are gnathobases, and not the axis or corm.
We are also, by the isolation of Peripatus and the impossibility of tracing to it all other tracheate Arthropoda, or of regarding it as a degenerate offset from some one of the tracheate classes, forced to the conclusion that the tracheae of the Onychophora have been independently acquired.
In Peripatus the stigmatic pits at which the tracheae communicate with the atmosphere are scattered and not definite in their position.
(Compare the definition of the class Chilopoda.) The movement of the legs in Diplopoda is like that of those of Peripatus, of the Phyllopod Crustacea, and of the parapodia of Chaetopoda, symmetrical and identical on the two sides of the body.
Our general conclusion from a survey of the Arthropoda amounts to this, that whilst Peripatus, the Diplopoda, and the Arachnida represent terrestrial offshoots from successive lower grades of primitive aquatic Arthropoda which are extinct, the Crustacea alone present a fairly full series of representatives leading upwards from unspecialized forms. The latter were not very far removed from the aquatic ancestors (Trilobites) of the Arachnida, but differed essentially from them by the higher specialization of the head.
=Onychophora (Peripatus, eec.).
PERIPATUS, a genus of animals belonging to the air-breathing division of the phylum Arthropoda.
Peripatus capensis, drawn from life.
As already stated, Peripatus is viviparous.
- Peripatus capensis dissected so as to show the alimentary canal, slime glands and salivary glands.
- Brain and anterior part of the ventral nerve-cords of Peripatus capensis enlarged and viewed from the ventral surface.
- Male Generative Organs of Peripatus capensis.
Peripatus is found in Africa, in Australasia, in South America and the West Indies, in New Britain, and in the Malay Peninsula and Sumatra.
It thus appears that in Peripatus the coelom does not develop a perivisceral portion, but gives rise only to the renal and reproductive organs.
The genus Peripatus was established in 1826 by L.
Peripatus is an Arthropod, as shown by (1) the presence of appendages modified as jaws; (2) the presence of paired lateral ostia perforating the wall of heart and putting its cavity in communication with the pericardium; (3) the presence of a vascular body cavity and pericardium (haemocoelic body cavity); (4) absence of a Derivisceral section of the coelom.
Finally, the tracheae, though not characteristic of all the classes of the Arthropoda, are found nowhere outside that group, and constitute a very important additional reason for uniting Peripatus with it.
Peripatus, though indubitably an Arthropod, differs in such important respects from all the old-established Arthropod classes, that a special class, equivalent in rank to the others, and called Prototracheata or Onychophora, has had, as we have seen, to be created for its sole occupancy.
The Annelidan affinities are superficially indicated in so marked a manner by the thinness of the cuticle, the dermomuscular body-wall, the hollow appendages, that, as already stated, many of the earlier zoologists who examined Peripatus placed it among the segmented worms; and the discovery that there is some solid morphological basis for this determination constitutes one of the most interesting points of the recent work on the genus.
The genus Peripatus, so far as adult conformation is concerned, is a very homogeneous one.
(The following genera have been proposed: Peripatus for the neotropical species, Peripatoides for the Australasian, Peripatopsis and Opisthopatus for the African, Paraperipatus for the New Britain, Eoperipatus for the Malayan species, and Ooperipatus for the supposed oviparous species of Australia and New Zealand.) The colour is highly variable in species from all regions; it is perhaps more constant in the species from the neotropical region than in those from elsewhere.
- A series of diagrams of transverse sections through Peripatus embryos to show the relations of the coelom at successive stages.
The following species are aberrant in respect of these characters: Peripatus (Opisthopatus) cinctipes, Purcell (Cape Colony and Natal), presents a few Australasian features; there is a small receptaculum seminis on each oviduct, some of the legs are provided with welldeveloped coxal organs, the feet have one anterior, one posterior and one dorsal papilla, and the successive difference in the ages of the embryos in the uterus, though nothing like that found in the neotropical species, is slightly greater than that found in other investigated African species.
Bouvier, "Sur l'organisation du Peripatus tholloni, Bouv.," Comptes rendus, cxxvi.1358-1361(1898); "Contributions a l'histoire des Peripates Americains," Ann.
Fletcher, "On the Specific Identity of the Australian Peripatus, usually supposed to be P. leuckarti, Saenger," Proc. Linn.
Moseley, "On the Structure and Development of Peripatus capensis," Phil.
Purcell, "On the South African Species of Peripatus," &c., Annals of the South African Museum, i.
Sclater, "On the Early Stages of the Development of a South American Species of Peripatus," Quart.
Sedgwick, "A Monograph of the Development of Peripatus capensis" (originally published in various papers in the Quart.
1 -146 (1889); "A Monograph of the Species and Distribution of the Genus Peripatus, Guilding," Quart.
Sheldon, "On the Development of Peripatus novae zealandiae," pts.
Steel, "Observations on Peripatus," Proc. Linn.