199 



TABLE I 



The Limbs of the Crayfish 



Segment 



Head-< 



I 



2 



5 

 6 



7 

 8 



Thorax-* 



lO 



II 



12 



13 



Abdomen-: 



15 



i6 



i7| 



18 



IQl 



20 



Name 



No appendage 

 Antennule 

 (ist antenna) 



Antenna 

 (2nd antenna) 



Mandible 



Maxillule 



(ist maxilla) 

 Maxilla 



(2nd maxilla) 



ist maxilliped 

 2nd maxilliped 

 3rd maxilliped 



Pincers 



(forceps, 



cheliped) 

 ist walking leg 

 2nd walking leg 



3rd walking leg 



4th walking leg 



Swimmerets 



Swimmerets 



Swimmerets 



Paddles 



Function 



Sensory 



Sensorj' 



Feeding 



Feeding 

 Respiratory 



Respiratory 



and feeding 

 Respiratory 



and feeding 

 Respiratory 



and leeding 

 Fighting, 



holding 



Walking 

 Walking and 



sexual 

 Walking 



Walking and 

 sexual 



Sexual 



Swimming 

 and sexual 



Swimmmg 

 and sexual 



Swimming 



Structure 



Three basal segments. 

 Two branches, probably 

 not homologous with 

 endopodite and exopo- 

 dite. Bears statocyst. 



Long endopodite. 

 Bears opening of green 

 gland. 



Toothed biting base and 

 short 2-segmented endo- 

 podite making the palp. 



Three flat plates. 



Several lobes. The exo- 

 podite forms the scapho- 

 gnathite or baler, which 

 maintains a current of 

 water over the gills. 



Large exopodite and epi- 

 podite. 

 Similar to ist maxilliped. 



Typical structure. 



No exopodite. Very 

 large endopodite with 

 grasping chelate end. 



As last, but much smaller. 



As last. Bears genital 

 opening in female. 



As last, but not chelate. 

 No genital opening. 



As last, but no epipodite. 

 Pears sexual opening in 

 male. 



Form canal for seminal 

 fluid in male ; vestigial in 

 female. 



Modified in male ; flat- 

 tened endopodite and 

 exopodite in female. 



Flattened endopodite and 

 exopodite ; carry eggs in 

 female. 



Large flattened endo- 

 podite and exopodite 

 form, with telson, the 

 tail fan. 



