ANATOMY OF AN AKTHROPOD. 



95 



end of the short small intestine or ileum is marked by the 

 attachment of a number of fine glandular tubes known as MdL- 

 pighian tubules {Mc), which are probably excretory organs. The 

 colon or large intestine (Li) is wide and long, and terminates in 

 a short dilated terminal part, tlie rectum (R). At the anterior 

 end of the mesenteron will be seen seven convuluted club- 

 shaped diverticula called hepatic cceca (H). (Five only are 

 represented in the figure.) 



The Respiratory System consists of a series of tubes containing 



---&. 



~C. 



n 



Pia. 86.-1, Tbaohba, and ii, Side-view of part of Abdomen, showing spiracle (Sp). 

 T, Tergum ; S, sternum ; a, spiral fibre ; 6, inner coat ; c, outer coat 



air. This can be easily demonstrated by plunging the opened 

 cockroach under water, when the tubes will be shown as silvery 

 threads, due to the contained air in them. These air-tubes or 

 trachecB (fig. 35, i.) commence at the spiracles and run to all 

 parts of the body. "When minutely examined the tracheae will 

 be seen to be circumscribed by a dark spiral band (a). Ee- 

 spiration takes place by these tubes, carrying the air to all parts 

 of the body and its organs, hence blood-vessels are not so neces- 

 sary as when one definite area only is for respiratory func- 



