How to use Peripatus in a sentence
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.
The possession of gill-slits is as interesting a feature in the organization of Balanoglossus as is the presence of tracheae in Peripatus.
In Peripatus they occur in every somite of the body.
Peripatidea (see Peripatus).
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.Advertisement
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.
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.
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.Advertisement
In Peripatus the stigmatic pits at which the tracheae communicate with the atmosphere are scattered and not definite in their position.
The somites following the head are strictly nomomeristic and nomotagmic. The first three form the thorax, thhe appendages of which are the walking legs, tipped with paired claws or ungues (compare the homoplastic claws of Scorpio and Peripatus).
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.
As already stated, Peripatus is viviparous.
Peripatus is found in Africa, in Australasia, in South America and the West Indies, in New Britain, and in the Malay Peninsula and Sumatra.Advertisement
It thus appears that in Peripatus the coelom does not develop a perivisceral portion, but gives rise only to the renal and reproductive organs.
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.Advertisement
The genus Peripatus, so far as adult conformation is concerned, is a very homogeneous one.
Fletcher, "On the Specific Identity of the Australian Peripatus, usually supposed to be P. leuckarti, Saenger," Proc. Linn.
Eoperipatus, Peripatopsis, Opisthopatus, &c. (See Peripatus.) Grade C (of the Arthropoda).