224 



COLLEGE ZOOLOGY 



present in only a few of the many available 

 habitats. This seems to indicate that this 

 group once had a continuous distribution 

 but that it has disappeared throughout most 

 of its range and is on the road to extinction. 

 Peripatus lives in crevices of rock, under 

 bark and stones, and in other dark moist 

 places and is active only at night. When 

 irritated, it throws a jet of slime, sometimes 

 to a distance of almost a foot, from a pair of 

 glands which open on the oral papillae. 



This slime sticks to everything but the body 

 of the animal itself; it is used principally to 

 capture flies, wood lice, termites, and other 

 small animals; and, in addition, is a weapon 

 of defense. A pair of modified appendages 

 serve as jaws and tear the food to pieces. 



Most of the 70 known species are vivipa- 

 rous, and a single large female may produce 

 30 or 40 young in a year. These young resem- 

 ble the adult when born, differing mainly 

 in size and color. 







f^^o;^ oS^.o oo ^ooq .0° S(?.o:p ° 0. 



.6^£p .0. 9 oP° qO o?°ei^?n ° 





Teeth Antenna 

 Oral papilla 



Figure 125. Peripatus. Left, ventral view, the legs are stubby and unlike those of typical 

 arthropods, but the claws are arthropodlike. In each jaw are embedded two backward-pointing, 

 clawlike teeth. Right, lateral view, the "head" bears two extensible antennae, near the base of 

 which is a pair of simple eyes. The numerous papillae which cover the whole body give it a 

 velvety texture. 



The internal anatomy is a combination 

 of annelidlike and arthropodlike structures. 

 The chief systems of organs are arranged as 

 in annelids; the nephridia are paired and 

 segmental in distribution, and the reproduc- 

 tive organs are supplied with cilia. Cilia do 

 not occur in arthropods. The arthropod 

 characteristics include jaws derived from ap- 

 pendages, a body cavity that is a hemocoel, 



tracheae, and the almost complete absence 

 of a coelom around the digestive tract. 

 Peripatus differs from both annelids and 

 other arthropods in the possession of a single 

 pair of jaws, in scant metamerism, in the 

 arrangement of the tracheal openings, in 

 the texture of the skin, and in the separate 

 nerve cords with no well-developed ganglia. 

 Hence, the onychophorans do not fit the 



