SECT. Ill 



THE A P P E N D AC E S 



37 



cirrus forming the cxopoditc. As the larva grows, 

 the cndopoditc gradual ly degenerates, leaving the 

 sensor}- cirrus to form the distal end of the limb 

 which is thus a sensor}' organ (compare also Figs. 

 34 and 35). 



III. The Alamliblcs- -These are the first limbs which 

 admit of undoubted comparison with parapodia. We 

 find, however, that while the dorsal branch has entirely 



v 



FIG. 8. A, diagram of mandible; s, shell-fold. At d the dorsal parapodium has 

 disappeared, but is indicated by the musculature. ?', ventral parapodium form- 

 ing the mandible itself, the musculature coming from the sternal plate (./). />', 

 diagram of ist maxilla. At </, a larger rudiment of the dorsal parapodium is 

 retained than in the mandible. 



disappeared, the ventral has grown enormously in all 

 directions to form the powerful masticatory limbs 

 which are such a striking feature in the Apodidae. 

 That these mandibles arc homologous with the gnatho- 

 bases of the trunk limbs, and therefore, according to 

 our view, with the ventral parapodia of the Annelida, 

 may be seen at once by comparing their muscles with 



