180 PERIPATUS, MYRIAPODS, AND INSECTS. 



cate, indeed, that they seem to be able to perceive the nature of 

 objects without actual contact. 



Chapter II treats of the class Myriapoda, a class of animals 

 which are widely distributed, and are represented in almost every 

 part of the world. Heat and cold alike seem to offer favourable 

 conditions for their existence, and they flourish both in the most 

 fertile and the most barren countries. 



One of the most important characteristics which distinguish 

 Myriapods from other Arthropods is the fact that they possess, on 

 the posterior segments of the body, true legs which are jointed 

 and take part in locomotion. The head is in all cases quite dis- 

 tinct from the body, and may be regarded as a number of seg- 

 ments fused together into one mass. Their heads are always 

 provided with a single pair of antennse and mouth appendages, 

 consisting of an upper lip, a pair of mandibles or jaws, and one 

 or two pairs of maxillae. 



Their internal structure has a great likeness to that of insects. 

 The general position of the internal organs may be seen from Fig. 

 II, which shows a Lithobius dissected so as to exhibit the digestive 

 and nervous system : — 



The digestive canal, which is a straight tube, extends through- 

 out the whole length of the body, and terminates in the last 

 segment of the body. 



The heart has the form of a long, pulsating, dorsal vessel, 

 which extends throughout the whole length of the animal. It is 

 divided into a number of chambers which are attached to the 

 dorsal wall of the body, and are furnished with muscles of a wing- 

 like shape, which are known as the alary muscles and which 

 govern the pulsations. The chambers are furnished with valves 

 and arteries for the exit of blood, and slits known as ostia for the 

 return of blood to the heart. 



The remaining chapters of the book treat of the following 

 Orders of Insects, viz. : — Aptera, Orthoptera, Neuroptera, 

 and a portion of Hymenoptera, 



Insects form by far the larger part of the land animals of the 

 world. They outnumber in species all the other terrestrial ani- 

 mals together, while, compared with the Vertebrates, their numbers 

 are simply enormous. Yet they attract but little attention from 



