12 



DIVISIONS OF ARTICULATA. 



circulatory apparatus is less complete, and in some cases is alto- 

 gether absent. 



10. In a word, we see that articulated animals are chiefly dis- 

 tinguished from the other three branches of the animal kingdom 

 by the arrangement of the nervous system and by the body being 

 surrounded by a series of rings which seem to divide it into so 

 many transverse segments. 



11. This great branch of the animal kingdom is composed of 

 six distinct classes of animals ; namely, insects, my'riapods, 

 arach'nidans, crusta'ceans, cirr'hopods, and anne'lidans. The 

 following table exhibits some of the characters by which they 

 are distinguished from each othe,r. 



Blood white; 

 provided with 



lungs, or 



trachese for 



breathing air. 



Extremities 



articulated. 



CLASSES. 



INSE'CTA. 



MYRI'APODA, 



branchiae for 

 breathing wa- < 

 Uer. 



A distinct head, 

 thorax and abdomen ; 

 three pairs of legs, and 

 generally provided with 

 wings. Tracheae : but 

 no circulatory appara- 

 tus properly so called. 



Head, thorax, and " 

 abdomen, not separated 

 from each other. Legs, 

 twenty-four or more 

 pairs. Tracheae : no 

 circulatory apparatus: 

 without wings. 



Head confounded " 

 with the thorax. Al- 

 ways without wings. 

 Four pairs of legs. 

 Tracheae, or pulmonary 

 sacs. Vascular system 

 tolerably well develop- 

 ed. 



In general, five or' 

 seven pairs of articu- 

 lated legs. A circula- 

 tory apparatus. 



No legs for locomo- i 

 tion. Always live at- > CIRR'HOPODA. 

 tached to other bodies. j 



> ARACH'NIUA 



lied or coloured blood. Unprovided with articulated 

 extremities. Generally having branchiae. 



. , 

 A 



10. How are articulated animals distinguished from the other three 

 Branches of the animal kingdom ? 



11. Into what classes is the Branch of articulated animals divided ? 



