TRACHEA TA 317 



chambers ; these facts, together with others derived from em- 

 bryology, show that each tergum corresponds with two primitive 

 somites. The legs have five joints and a terminal claw. 



Segments and Appendages of lulus. 



1. Antennae. ,. 5. One pair of legs. 



2. Mandibles. I „ „i, .1 ■ 6. This segment bears no legs. 



3. Maxillae, fused across the f '7. One pair of legs. 



middle line. -' 8. The succeeding segments bear two 



4. Leg-like appendages, modified in male. pairs of legs. 



The cephalic appendages comprise a pair of antennae, a pair 

 of mandibles with broad crushing surfaces, and a pair of 

 maxillae which have fused across the middle line and which 

 form a bilobed plate. The appendages are borne on the head ; 

 the first post-cephalic segment has a broad tergum, and bears 

 ventrally a pair of leg-like appendages, which are turned 

 forward, and probably assist in the act of feeding ; the same 

 appendage is in some species modified in the male, and forms 

 a blunt hook -like process. The second post-cephalic segment 

 bears a normal pair of legs, the third has none, and the 

 fourth one pair, the succeeding segments have two. The 

 generative orifice in both sexes is on the third segment, just 

 behind the bases of the second pair of legs. In the male 

 the seventh post-oral segment bears only one pair of legs 

 and a complex copulatory apparatus not connected with the 

 internal organs. This apparatus is of great systematic value. 

 The female luluSj like that of GeapJiilus, watches over its 



eggs. 



Some genera of the Polyzonidae, e.g. Siphonophora (Kg. 

 182), have the anterior part of the head and the mouth- 

 parts prolonged into a sucking or piercing snout. Most of 

 the Diplopoda possess a series of glands which open to the 

 exterior by a row of lateral foramina repugnatoria, one on 

 each segment ; these emit an offensive fluid ; in one species, 

 Fontaria, this fluid breaks up into prussic acid and benzal- 

 dehyde (oil of latter almonds). 



Except in Glomeris, where the tracheae are branched as 

 in the Chilopods, the respiratory organs resemble those of 

 Peripatus. The stigma opens into a tracheal sac, from which 

 a number of short unbranched tracheae arise. There are four 

 of these on each segment. The Glomeridae have shortened. 



