INVERTEBRATE ZOOLOGY. 37 



Sub-class I. Onychophora This includes one genus of wideh' sepa- 

 rated species, intermediate between An- 

 nelids and Myriapods. The body is worm- 

 like. each segment bearing a pair of 

 limbs with indistinct articulations, thus 

 resembling parapodia. Paired nephridia 

 of Annelid type, opening at the base of 

 the feet. A richly branched tracheal 

 system, opening by irregularly dispersed 

 stigmata, -jf Peripatus. 



Sub-class II. Myriapoda Head with antennae, mandibles, and two 



pairs of maxillae. No differentiation of 

 thorax. Each segment bears a pair of 

 legs, alike in shape and size. 



Order 1. Chilopoda Mainly depressed in form. One pair of 



legs to each segment. Mandibles well 

 developed, fitted for predaceous life. 

 First pair of legs transformed to a pair 

 of jaws furnished with ])oison glands. 

 Reprodiictive opening at posterior end of 

 body. -^ Lithohiiis, Scolopendrxi. 



Order '3. Diplopoda A double pair of legs to each segment. 



Maxillae united to form a complex under- 

 lip, the gnathochilarium. Reproductive 

 opening at base of .second pair of legs. 

 ■^ lulus. 



Sub-class. Hexapoda (Insecta) Body divided into three distinct regions, 



or segment-complexes, head, thorax and 

 abdomen. Mouth parts typically of three 

 component parts, the mandibles, and the 

 first and second maxillae, which may be- 

 come strongly modified in adaptation to 

 very varied life habits. Thorax of three 

 segments, each one with a pair of legs. 

 The last two segments in higher insects 

 bear each a jiair of wings formed by an 

 integumental duplicature and directly de- 

 rivable from " tracheal gills," a modifica- 



