316 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 
h m 
Fra. 181.—Inner view of the sterna of a single segment of Judws londonensis, much en- 
larged to show the structure and arrangement of the tracheal organs. After Voges. 
The two pairs of tracheae are seen 7 sifu, the posterior pair overlapping the anterior, 
h. The posterior margin of the body ring st. Tubular chamber of tracheae. 
(tergum). t, Fine tracheae given off from it. 
7. Anterior border; between thetwolie ms. Respiratory muscle attached to 
the two terga. tracheal sac. 
m, Wentral body muscle, 
beimg 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 54, inch long, is covered with tufts of hairy scales, 
probably defensive. 
The commonest genus of Diplopoda is ulus; a good 
many species of this genus occur in Britain, the most frequent 
being Julus terrestris, 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 
