RELATIONS OF INSECTS TO OTHER ARTHROPOD A 23 



median pieces of the gnathochilarium of Diplopoda. Hypopharynx? 

 Epipharynx ? 



Trunk with from fifteen to sixteen dorsal, more or less free subequal 

 scutes, the first the smallest. Pedigerous segments twelve; also twelve 

 pairs of 5-jointed legs, which are of nearly equal length, the first pair 4; 

 the others 5-jointed, all ending in two claws, as in Synaptera and winged 

 insects. A pair of 1 -jointed anal cerci homologous with those of Thy- 

 sanura and Orthoptera, into each of which opens a large abdominal 

 silk-gland. Abdominal segments with movable styles or "pseudopods" 

 (" Parapodia " of Latzel and of Schmidt), like those of Campodea and 

 Machilis, and situated on the base of the coxal joint in front of the ven- 

 tral sac. Within the body near the base of each abdominal style is an 

 eversible coxal sac or blood-gill (Fig. 15, eg). The single genital opening 

 is on the fourth trunk-segment in both sexes (Fig. 15, indicated by the 

 arrow]. The malpighian tubes (ur. t) are two in number, opening into 

 the digestive canal at the anterior end of the hind intestine; they extend 

 in front to the third or second segment from the head. They are broad 

 and straight at their origin, becoming toivards the end very slender and 

 convoluted. 



The three divisions of the digestive track are as in insects, the epithe- 

 lium of the mid-gat being historically as in Campodea and Japyx; 

 rectal glands are present. A pair of very large salivary glands are 

 situated in the first to the fourth trunk-segments, consisting of a glandu- 

 lar portion with its duct, which unite into a, common duct opening on 

 the under side of the head, probably in the labium. 



But a single pair of stigmata is present, and these are situated in the 

 front of the head, beneath the insertion of the antennas and ivithin the 

 stipes of the mandibles; the tracheae are very fine, tvithout spiral threads 

 (taznidia), and mostly contained within the head, two fine branches 

 extending on each side into the second trunk-segment. 



After birth the body increases in length by the addition of new seg- 

 ments at the growing point. 



In respect to the nervous system, there are no diagnostic charac- 

 ters ; there are, however, not as many as two pairs of ganglia, to a 

 segment. The brain is well developed, sending a pair of slender 

 nerves to the small eyes. The ganglia of the segment bearing the 

 first pair of legs is fused with the suboesophageal ganglion. Grass! 

 was unable to detect a true sympathetic system, but he suspects the 

 existence of a very small frontal. ganglion. 



The slender dorsal vessel, provided with ostia and valvules, pul- 

 sates along the entire length of the trunk; an aorta passes into the 

 head. 



