182 



body immediately surround tin- mouth, and are so constructed 

 as to form instruments of locomotion, instrument* of pre- 

 hension liy their tree extremities, and of jaws by their base; 

 but, as might be anticipated this very cumulation of func- 

 tions renders them less appropriate for the advantageous 

 performance of any special function. But in animals of the 

 same class with faculties more perfect, these different func- 



Fig. 121. Limulus.* (Molucca Crab.) 



tions are no longer performed by one and the same organ or 

 instrument; each function belongs to a distinct organ, and 

 } f et these organs are still the same limbs or members, of 

 which some are exclusively destined to mastication, others to 

 prehension, and others to locomotion. In the craw-fish (ecre- 

 visse), or lobster, for example (Fig. 122), the limbs sur- 

 rounding the mouth are exclusively arranged for mastication ; 



The animal is represented as seen from below : b, the mouth ; p, feet, 

 whose base performs the office of jaws ; a, abdominal appendages carrying 

 branches; q, caudal stylet. 



