CRUSTACEA CONSIDERED AS A CLASS. 

 FIG. 477. 



351 



First pair of tho- 

 racic leet.. . . 



Auditory tubercle. 



Mouth inclosed by 

 mandibles or 

 mandible-feet. . 



Fifth pair of tho- 

 raciclocoruotive 

 organs 



J ...1JS._. Eyes. 



Antennae, first pair. 

 Anteunse, second 



pair. 



Abdominal locomo- 

 tive appendages. 



Vent. 

 \, Caudal fin. 



A Crustacean Craw-fish as seen from below. 



although they are modified so as to perform very many 

 and various functions, as those of antennae, eyes, 

 jaws, claws, feet, paddles, and tail that is, these appar- 

 ently very different organs are only modified locomotive 

 appendages ! 



The mouth is situated underneath and somewhat 

 back from the anterior border of the head. The 

 gullet is short, the stomach large, and the intestines 

 slender. 



The blood is colorless, or nearly so, and is kept in 

 motion by a heart situated just under the top of the back, 



