XII] PROTOTKACHEATA 225 



Carboniferous. The carapace is completely absent, the eyes are 

 stalked and movable, the thoracic legs have oval exopodites formed 

 with setae and each leg bears two epipodites which act as gills. 



Class II. ANTENNATA. 

 Sub-class A. PROTOTRACHEATA (Onychophora). 



A short account of these creatures all of which used to be included 

 in the genus Peripatus must be given, as they are of a very primitive 

 nature and in both their adult structure and the mode of its develop- 

 ment throw much light upon the origin and anatomy of Myriapods 

 and Insects and indeed on the Arthropods generally. 



The different species of Peripatus are differently coloured, but 

 they mostly possess a beautiful velvety coat. In shape they 

 resemble caterpillars but carry two large antennae on their heads, 

 and at the base of each antenna is an eye. On the under surface 

 of the head is the mouth and tucked into it on each side is a 

 toothed jaw. This is an appendage which has been modified so as 

 to form a true gnathite. At each side of the mouth is a third pair 

 of appendages, the oral papillae, from the tips of which a sticky 

 slime can be ejected which entangles the insects and spiders on 

 which the animal lives. The other appendages, which vary in 

 number in the different species from seventeen pairs to over forty, 

 have the form of soft cylindrical papillae ending in two claws and 

 function as walking legs (Fig. 92). The anus is posterior, and at 

 the base of each leg is a slit-like pore, the opening of an excretory 

 organ. The genital pore is in front of the anus. 



FIG. 92. Peripatus capensis x very slightly. From Sedgwick. 



The body cavity is a spacious haemocoele divided into three longi- 

 tudinal compartments by two bands of muscles which run from 

 its outer upper angle towards the mid-ventral line. The lateral 

 compartments are continuous with the cavities of the limbs and 

 lodge the excretory organs which are coelomiducts but are usually 

 termed "nephridia," the salivary glands and the nervous system'. 

 The alimentary canal, slime glands and generative organs lie in the 

 middle compartment. 



The mouth leads into a large muscular pharynx, such as is 

 found in many Chaetopods. The salivary glands open near this. They 

 s. & M. 15 



