Homology 577 



Fig. 307. — Crayfish appendages (Cambarus sp.) to show homology. Appendages 

 are numbered from I to XIX j removed from the left side and drawn to scale. 

 Appendages XIV and XV are drawn from both male and female crayfishes. 1, 

 Protopodite; 2, endopodite; 3, exopodite; 4, epipodite; 5, epipodite with gill fila- 

 ments; 6, gill with gill filaments; 7, chitinous threads. Appendage I is the anten- 

 nule (first antenna) ; II, the antenna; III, mandible for chewing; IV- V, first and 

 second maxillae; VI-VIII, first, second, and third maxillipeds; IX-XIII, walking 

 legs; XIV-XVIII, swimmerets; XIX, uropod (sixth swimmeret). (See Fig. 128.) 



