586 CLASS III. MYRIAPODA. 



segment, but inasmuch as . it may coexist with both pairs of 

 legs (Callipodidae) it is regarded by Silvestri as an organ sui 

 generis. It consists usually of two pairs of leg-like processes 

 and is used for transferring the sperm to the vulva of the female 

 in copulation. In the female this apparatus is absent and the 

 legs of the segment concerned are normally present. The varia- 

 tions presented by the auxiliary copulatory apparatus are of 

 considerable importance in the classification. 



In all Diplopods the genital openings are paired and placed 

 in both male and female, on the ventral surface between the 

 2nd and 3rd pairs of legs either between the 2nd and 3rd seg- 

 ment or on the 3rd segment, or on the coxae of the legs of the 

 2nd pair. In the male there is often a freely-projecting double 

 penis at the end of which the opening is placed. The penis is 

 not apparently used in the sperm transference (except possibly 

 in the Polyxenidae) ; this being effected by the above mentioned 

 copulatory appendages which are actually inserted into the 

 vulva.* 



The alimentary canal consists of a narrow oesophagus 

 (stomodaeum), into which, at the base of the gnathochilarium, 

 open the two salivary glands ; a midgut or intestine (mesenteron) 

 which is a wide tube beset with short liver diverticula and often 

 presents transverse marks which correspond with the segments ; 

 and a hind gut (proctodaeum), which receives at its junction 

 with the midgut two or four malpighian tubes. In Glomeris 

 the intestine is slightly curved. 



In the central nervous system, the nerves to the jaws are 

 given off by the suboesophageal ganglion. The ventral nerve- 

 cord extends the whole length of the body. Its ganglia are 

 more or less approximated ; but each double segment possesses 

 two, and the ganglia of the first three postcephalic segments 

 are more closely united than the others, though there is not the 

 same degree of differentiation into a thoracal and abdominal 

 nervous region that is found in the Chilopoda. 



The special sense organs are represented by the aggregated 

 simple eyes (p. 329), by the olfactory hairs on the antennae and 

 a tuft on the gnathochilarium, and by the organ of Tom 6s vary 



* Fabre (Ann. Sci. Nat. (4), Zool., 3, 1855) states that in Polyxenidae 

 and Julidae copulation takes place in September in captive animals, and 

 that light has a powerful influence in bringing it on. Sinclair has 

 observed it in May in Julidae, and in June in Polydesmidae, 



