96 NATURAL HISTORY OF ARTHROPODS. 



SUB-CLASS I. MALACOPODA. 



To this division of insects (for which the name Protracheata has also been proposed) 

 belongs the single genus Peripatus. In the early part of the present century the Rev. 

 Lansdown Guilding described the first species, from the West Indies, under the name 

 Peripatus iuliformis, the specific name alluding to its general resemblance to the galley 

 worms. Other forms have since been described from South America, New Zealand, 

 and the Cape of Good Hope. Mr. Guilding was under the impression that this form 

 belonged to the molluscs ; but subsequent students assigned it a place among the 

 worms, through its affinities to the insects, and especially to the myriapods, were hinted 

 at. In 1874 Mr. Moseley, one of the naturalists of the " Challenger " expedition, 

 described the anatomy of the species occurring at the Cape of Good Hope, and set at 

 rest all questions regarding the systematic position of Peripatus. 



Peripatus is strikingly like a myriapod in general appearance. It has a long body, 

 which is supported on numerous legs, varying in number from seventeen and nineteen 

 to thirty and thirty-three in the different species. The head bears a pair of ringed 

 antennae, and at their bases are a pair of simple eyes. On the lower surface of the head 

 is the mouth, armed with two pairs of laterally moving jaws, and at each side of the 

 mouth is a small papilla, at the summit of which a slime gland opens. 



FIG. 131. Peripatus, enlarged three times. 



The alimentary canal is nearly straight, and is composed of a narrow oesophagus 

 and intestine, and a broader stomach. A pair of salivary glands are also present. 

 The heart is a simple tube, and is but little specialized. The nervous system has 

 already been referred to. 



The most interesting anatomical feature is the respiratory apparatus. Scattered 

 over the surface of the body are the spiracles, but in certain regions, as between the 

 bases of the legs, they are most numerous. Each spiracle opens into a short tube, 

 from which arises a bunch of fine tracheae. These tracheae but rarely branch, and have 

 the spiral filament very imperfectly developed. The sexes are separate, and the young 

 undergo a large part of their development within the mother. But little is as yet 

 known concerning the embryology of this form, although the subject has been studied 

 by such masters as Balfour, Moseley, and Sedgwick. 



