flab 



A. Maxilla of lobster with its flve lobes (1-5) corresponding to the endites of the Phyllopod 

 thoracic limb. 



B. Section through the thorax of Apus. en, 1-6, the six endites; ex, exopodal or respira- 

 tory portion of the limb; c, carapace; ht, heart: m, intestine; ng, ganglion. 



C D 



-lit 



int 



C. Partly diagrammatic section through the thorax of Nebalia. en, the axial-jointed 

 endopodite; ex, exital portion or gill (above irregularly dotted) and flabellum below with rows 

 of dots; c, carapace. 



D. Actual section through the abdomen of Limulus; c, carapace; ht, heart; int, intestine; 

 ng, ganglia (lettering being the same as in C); en, axial- jointed endopodite; ex, exital or 

 respiratory portion bearing the gill-lamellae; the outer division (ex) homologous with the 

 exopodal portion of the phyllopod and phyllocaridan appendage. 



HOMOLOG1ES OF THE CRUSTACEAN AND LIMULUS LIMBS. 



[To face page 270.] 



