98 MYKIAPODA. 



like those of the Annelidans, composed of a dense, 

 semi-calcareous, or else of a firm, horny substance, 

 and to every segment is appended one or two pairs 

 of articulated legs, generally terminated by simple 

 points. 



The anterior segment, or head, besides the organs 

 belonging to the mouth, contains the instruments of 

 sense, consisting of simple or compound eyes, and of 

 two long and jointed organs, called antennae, gene- 

 rally regarded as ministering to the sense of touch, 

 but which are probably connected with other per- 

 ceptions unintelligible to us. 



The air required for respiration is taken into the 

 body through a series of minute pores, or spiracles, 

 placed on each side along the entire length of the 

 animal, and is distributed by innumerable ramifying 

 tubes or tracheae, to all parts of the system. The 

 number of segments, and consequently of feet, in- 

 creases progressively with age ; a circumstance which 

 remarkably distinguishes the myriapoda from insects 

 properly so called. There are two families belong- 

 ing to this class the millepedes or Julidae, which 

 feed on vegetable substances, and the Scolopendridae,' 

 or centipedes, which are carnivorous and rapacious. 



The Millepedes* (Julus\ are distinguished by their 

 nearly cylindrical form (Fig. 67), their slow gliding 



motion produced by 

 the alternate action of 

 their very numerous 

 little feet, sometimes 

 more than a hundred 



in number, and their habit of rolling themselves into a 

 close spiral, when touched. They resort to damp and 

 dark places, lurk under stones and moss, and are still 

 more commonly found beneath the bark and in the wood 

 of decaying trees. They are perfectly harmless, and feed 

 entirely on decomposing vegetable materials. For this 

 purpose their mouth is furnished with a pair of stout 

 horny jaws, which move horizontally, and are provided at 

 their cutting edges with sharp denticulations, so as to 

 * Mille, a thousand ; pes, a foot. 



