438 COMPARATIVE ANATOMY CHAP. 



CLASS II. Antennata. 



Systematic Review. 



Sub-Class I. Myriapoda. Millipedes. 



Trunk homonomously segmented, segments usually numerous, of nearly equal 

 size, and, except the last, provided with feet. "Without compound eyes. With 

 numerous ocelli. 



Order 1. Symphyla. 



With not more than 12 leg-bearing trunk segments. One pair of branched 

 tracheae, whose stigmata lie in the head. Unpaired genital aperture in the 4th 

 segment. Scolopendrella (Fig. 301, p. 444). 



Order 2. Chilopoda. 



Body more or less flattened dorso-ventrally. Each body ring carries only one 

 pair of limbs and answers to a segment. The two pairs of maxillae are separate. 

 The first pair of trunk feet moved on to the head as maxillipedes with poison glands 

 emerging on the terminal claw. Unpaired genital aperture on the penultimate 

 segment. Fam. Scutigeridce : with compound eyes. Trunk consists of 15 leg-bearing 

 segments. Scutigera. Fam. LithoUidce : trunk consists of 15 leg-bearing segments. 

 No compound eyes, but ocelli. LithoUus (Fig. 323, p. 464), Henicops. Fam. 

 Scolopendridce : with 21 or 23 leg-bearing trunk segments (the maxillipedal segment 

 not included). Body elongated. Scolopendra, Cryptops. Fam. Geophilidce : body 

 very long, with 31-173 leg-bearing trunk segments. GeopMlus, Himantarium. 



Order 3. Diplopoda (Chilognatha). 



Body mostly arched. From the 5th segment onwards each ring has 2 pairs of 

 legs and thus corresponds \vith a double segment. The two pairs of maxillae are 

 fused to form the so-called gnathochilarium. Without maxillipedes. Paired genital 

 apertures between the 2d and 3d pairs of legs. The legs of the 7th ring in the male 

 are changed into copulatory organs. Fam. Polyxenidce : 15 pairs of feet. Gnatho- 

 chilarium rudimentary. Copulatory feet wanting. Polyxenus. Fam. Glomeridce : 

 11-14 rings. Glomeris. Fam. Polydesmidce : without eyes. 19-20 trunk rings, 29- 

 31 pairs of feet. Polydesmus, Brachydesmus. Fam. Chordeumidce : 30 trunk rings, 

 45-50 pairs of feet. Atractosotna, Craspcdosoma, Chordeuma. Fam. Lysiopetalidce : 

 number of rings large, indefinite. Lysiopetalum. Fam. lulidce : 30-70 or more 

 rings. lulus. Fam. Polyzonidce : gnathochilarium reduced. Number of the rings 

 inconstant, 30-100 or more. Polyzonium. 



Order 4. Pauropoda. 



Feeler with several flagella. Only one pair of weakly developed maxillae. 10 

 trunk segments. 9 pairs of legs. Tracheae as yet not discovered. Genital apertures 

 at the base of the second pair of legs. Pauropus. 



Sub-Class II. Hexapoda. Insecta. 



Trunk heteronomously segmented ; the almost constant number of segments of 

 unequal size, the body is divided into head, thorax of 3 segments, and hind body of 

 10 segments. Each of the 3 thoracic segments has a pair of legs. Abdomen limbless. 

 Compound eyes as well as ocelli almost always present. Apertures of the sexual 

 organs always at the end of the hind body. 



