3i6 



ZOOLOGY 



between the two main subdivisions of the Myriapoda, for 

 although it is a vegetarian, and its generative organs open 

 anteriorly, it resembles the Chilopods in the bases of the legs 



Fig. 181. — Inner view of the sterna of a single segment of lulus londonensis, much en- 

 larged to show the structure and arrangement of the tracheal organs. After Voges. 

 The two pairs of tracheae are seen in situ, the posterior pair overlapping the anterior. 



The posterior margin of the body ring 



(tergum). 

 Anterior border ; between the two lie 



the two terga. 



St. Tubular chamber of tracheae. 

 t. Fine tracheae given off from it. 

 ms. Respiratory muscle attached 



tracheal sac. 

 m. Ventral body muscle. 



to 



being somewhat apart, and in the character of its filiform 

 spermatozoa, which are contained in spermatophores, as is 

 usually the case in the last-named order. Its body, which 

 is about 3^ inch long, is covered with tufts of hairy scales, 

 probably defensive. 



The commonest genus of Diplopoda is lulus; a good 

 many species of this genus occur in Britain, the most frequent 

 being lulvs terresfris, which is sometimes an inch or more 

 long, and is often to be found curled up under bark or stones. 

 In this animal the tergum forms an almost complete ring, 

 interrupted in the ventral line only by two sternal plates, 

 one in front of the other. In all the segments after the 

 fourth post -oral each of these plates bears a pair of legs, so 

 that each segment with its single tergum corresponds with 

 two pairs of legs, and has also two pairs of stigmata, one in 

 front of the base of each leg, two nerve ganglia, and two cardiac 



