THE MYR/APODA. 
413 
which is horny, and supports a pair of sharp hooked fangs re- 
sembling jaws, that move sideways, like the so-called mandibles of 
the spider. These jaws are, however, only modifications of the 
first feet, which are converted into instruments for killing prey, 
instead of moving their possessor from place to place, and each is 
perforated near its sharp termination with a long oval slit, through 
which venom is said to be instilled into the wound inflicted by this 
formidable weapon. 
The texture of the segments of the body of Julus is hard and 
brittle, but the rings of the Scolopcndra are flattened, and covered 
above and below with tough and leathery scales. Each segment, 
as has been stated above, in the Chilognatha, supports two pair of 
legs on each side on its under surface, but the first three segments 
only support a single pair. The last two segments are also 
without legs. The legs are short, feeble, and have several joints. 
In the Scolopcndra , however, the legs are long, strong, and very 
active; they have five joints, and terminate in a claw. Those 
attached to the segments near the head are small, but as they 
approach the hinder part of the body they increase in size 
and strength, the last pair being turned backwards. The number 
of the segments and legs appears to be constant in the adult 
Myriapod , but subject to important and remarkable increase during 
the progress of growth and development. 
A drawing of the alimentary canal of a Myriapod reminds us 
of that of the lepidopterous larvae. The oesophagus or gullet of 
Jidus tcrrcstris is capacious, the stomach is long and straight, and 
ends where the liver tubes enter, and an intestine straight and short 
succeeds. The salivary glands are folded up at the sides of the 
gullet, and the liver tubes pursue a tortuous course, and terminate 
at the end of the stomach. In fact, the resemblance is very 
great indeed. The respiratory organs are also similar as regards 
their arrangement in the two classes. The Myriapoda respire in 
the same manner as insects, by means of lateral spiracles and 
tracheal tubes. The spiracles are as visible on the sides of some 
Scolopendridcc as they are on the flanks of caterpillars, and the 
tracheae pass inwards in both instances, to be distributed over 
and amongst the internal organs. Moreover, the minute struc- 
tures of the tracheae are identical in the two classes, and the spiral 
