188 



ANIMALS WITH JOINTED LEGS— THE ARTHROPODS 



ences. They are all very efficient systems indicating the advanced de- 

 velopment of the arthropods. 



Digestive System. The crayfish is somewhat of a scavenger, eating 

 bits of dead animals that it may find, but also catching and eating live 

 water animals that get within reach of its powerful pinchers. After ob- 

 taining the food, the crayfish uses the pinchers, the maxillipeds, and the 

 maxillae as we use a knife and fork to cut up and carry the bits of food 

 to the mouth. The food is crushed into finer pieces by the mandibles 

 and passed through the short esophagus into the stomach. The an- 

 terior, or cardiac portion, of the stomach is for storage and is followed 



GILL 

 SEPARATOR 



ANTENNA 



NEPHRIDIOPORE 



1ST MAXlLLlPED 



GILL 



2ND MAXlLLlPED 



GILL 



3RD MAXILLIPED 



cf 1ST ABDOMINAL APPENDAGE* 



2ND ABDOMINAL APPENDAGE 



0*EN0 ABDOMINAL APPENDAOt 



SWIMMERCT 



UROPOD 



PROTOPOOITE ENDOPOOITE EPIPODITE EXOPODITF 



Biology, the Science of Life, McDougall and Hegner, The McGraw-Hill Book Co., Inc. 



Fig. 13.15. Some of the appendages of the crayfish dissected from the body to show 

 their structure better. Note how they have become modified to accomplish their 



particular purposes. 



