12 COMPARATIVE ANATOMY 



former coming into connection with the higher sense-organs, while 

 from the latter are developed the mechanisms for the taking in of 

 nutriment and for respiration. 



The anterior portion of the body, or liead, passes behind into 

 the trunk, either with or without the intermediation of a neck. The 

 coelome is practically restricted to the trunk, in the hinder part of 

 which the intestinal (anal) and urinogenital apertures are situated, 

 and posterior to which again is the tail. Head, trunk, and tail 

 constitute the body-axis, as distinguished from the liTnhs or 

 appendages, which arise from the trunk and of which there are 

 typically two pairs. 



