48 
The Queensland Naturalist June, 1939 
The chief characters which establish its place in the 
Arthropoda are as follows: — (a) the presence of a pair 
of jaws; (b) the presence of paired lateral ostia in the 
long* tube-like dorsal vessel ; (c) the haemocoelic body 
cavity, i.e., the whole of the body cavity not occupied by 
the digestive system and the generative organs is filled 
with blood; (d) the presence of tracheae, a character 
not found outside the phylum. On the other hand, the 
following features show that it has definite affinities 
with the Annulata: — (a) it has a pair of nephridia in 
every segment of the body behind the first two; (b) it 
has cilia in the generative tracts; (c) thin cuticle; (d) a 
layer of muscles in the body wall; (e) hollow appendages. 
Moreover it differs from all the rest of the Arthropoda 
in the following details: — (a) the number and arrange- 
ment of the spiracles; (b) the presence of only a single 
pair of jaws; (c) the texture of the skin; and (d) the 
simple nature of the body segments. Finally, it has a 
superficial resemblance to certain Mollusca because of 
the hollow, sensitive antennae and slug-like body. To 
quote Sedgwick: “Peripatus, therefore, is zoologically 
of extreme interest from the fact that, though in the 
main Arthropodan, it possesses features which are 
possessed by no other Arthropod, and which connect it 
to the group to which the Arthropoda are in the general 
plan of their organisation most closely related. ” 
Recently the Qnychophora has been divided into 
two families, each of which consists of two sub-families. 
The Australian forms are included in the family 
Peripatopsidae, sub-family Peripatoidinae. The number 
of Australian genera and species is doubtful, for some 
authorities consider that many of the so-called species 
are really only forms of one species. 
Peripatus is very sensitive to light and drought, 
and spends the day hidden in tiny crevices in damp rot- 
ting logs, under stones, under the bark of dead stumps, 
and probably in the soil. The late Dr. R. J. Tillyard 
was of the opinion that they kept just above the water- 
table, rising and burrowing in the soil with the rise and 
fall of the water. Their food probably consists of 
amphipods, isopods, collembola, mites, small diplopoda, 
and insect larvae which abound in their normal habitat. 
Specimens have been kept alive for several weeks on 
such a diet. No actual observations have so far been 
night. AYhen disturbed they have a habit of shooting 
out with considerable force a sticky slime which comes 
