EXPLANATION OF LETTERS USED IN THE TEXT-FIGURES. 



b. 



Dorsal bristles. 



V. 



Ventral bristles. 



bd. 



Dorsal division foot. 



bv. 



Ventral division foot. 



c. and so. 



Segmental organ. 



CO. 



Ciliated organ (ccelomostome). 



d. 



Alimentary canal. 



d'. 



Cseca of canal. 



do. 



Dorsal cirrus. 



dm. 



Dorsal longitudinal muscles. 



dv. 



Dorsal blood-vessel. 



hp. 



Hypoderm. 



iso. 



Internal end of nephridium with solenocytes. 



nc. 



Nerve-cords. 



np. 



Nephridiopore. 



npc. 



Nephridial canal. 



om. 



Oblique muscle. 



ov. 



Ova. 



sp. 



Spine. 



sol. 



Solenocytes. 



vc. 



Ventral cirrus. 



vm. 



Ventral longitudinal muscles. 



vv. 



Ventral blood-vessel. 



