

INTRODUCTION. 



The particular differences between the lower animals are generally but little observed. It is, there- 

 fore, well, .is introductory to the study <>f a certain set of animal-, to observe the place thty occupy in the 

 systematic arrangement of Natural History. This draws the attention of the student to their peculiarities, 

 and, at the same time acquaints him with all related and resembling famili* - 



The animal world has been divided into two parts, animals without a backbone (Inrerttbrat,c ) and 

 those vith a backbone ( Vcrtcbrattc) . The first part reaches from the lowest infusoria, hardly distinguish- 

 able from plant life, to the most perfect insect. It is divided into severed classes, of which the most 

 highly developed is that of jointed animals (. -Irtli rop^tia ). The bodies of these are encased in a scries of 

 rings, variously grouped and jointed together, which serve instead of bones to keep the bud}' in foiin. 

 This class consists of three orders, the Myriopoda or Centipedes, with a head and a row of equal rings, 

 many legs and no wings; the Insccta or true insects, with the rings grouped in three parts, head, breast 

 part and body part. All have six legs, a pair of feelers, (antcinuc') in their faces between the eyes, and 

 most of them have wings. 



The order of the .IracliiiiJa, spider-like animals, is placed between the myriopods and insects. They 

 have eight legs, no feelers between their eyes, but often a pair of leg-like feelers frum their mouth parts 

 (palpi] and no wings. The short-legged mites (Acarina) and long-legged harvestmen ( I'Iialan^i<iu} 

 have their head, chest and body part united to an oval-shaped body. The scorpions have a pair of 



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