234 LATERAL APPENDAGES OF CRUSTACEA. 



( 891 898). This comparative study of the teg umentary ske- 

 leton is of great interest as a department of Philosophic Anatomy ; 

 one of whose most important branches has reference to those mo- 

 difications, to which Nature subjects the same organic elements, 

 in order to adapt them to various purposes, and to create different 

 animals from analogous materials ; but the limits we have assign- 

 ed ourselves do not permit us to dwell longer on this subject. 



846. The lateral appendages of the different rings constituting 

 the body, are in general very numerous, and present consider- 

 able differences in their conformation and uses ; both when we 

 consider those in the different parts of the same individual, and 

 when we compare them in distinct species. Those of the first 

 pair are generally subservient to the animal functions, and sup- 

 port the eyes or constitute the antennae ; the next surround the 

 mouth, and serve for the prehension or division of the food ; 

 those of the middle part of the body constitute the legs for loco- 

 motion; and those which are placed behind have various 

 uses, but are generally subservient to respiration or reprodnc- 



pm 



FK;. 567. PRAWN : as, antennae of the first pair ; ai, antennae of the second pair ; 

 I, laminar appendage covering its base ; r, rostrum, or frontal prolongation of the 

 carapace ; y, eyes ; pm, external foot-jaw ; p , first thoracic member ; p", second 

 thoracic member ; fp, false legs, or swimming members, of the abdomen ; n, tail-fin. 



tion ; lastly, this long series ordinarily terminates by one or 

 several pairs of members, which serve as fins. 



847. The head, or rather the cephalic portion of the body, 

 carries the eyes, the antennae, and the appendages of the mouth. 



