80 



AETICULATED ANIMALS. 



portioned to the vigorous movements of which the 

 limbs are now capable. The rings of the body, 

 hitherto distinct, become more or less soldered to- 

 gether in those parts where the greatest strength and 

 firmness are necessary ; and scarcely any traces are 

 left to indicate their existence as separate pieces ; 

 so that, instead of exhibiting that succession of 

 similar segments seen in the centipedes, the body 

 becomes divided into three distinct portions ; namely, 

 the head 9 which contains the organs of the senses 

 and the parts of the mouth, the thorax, supporting 

 the limbs, or instruments of progression, and the 

 abdomen, enclosing the viscera subservient to nutrition 

 and reproduction. (Fig. 54.) 



In the fourth division of articulated animals, 

 namely, the Arachnida (scorpions, spiders, $c.) 9 a 



FlG. 55. SCORPION AND CENTIPEDE. 



still further consolidation of the external skeleton is 

 visible, for in these creatures even the separation 

 between the head and the thorax becomes obliterated, 



