Stritcf'ure of H(tl()()l(t'(i duh/a. 



409 



Fig. 0. — A ]H)rti(>n of tlie oral ni<ir;jin with a ])art of one linih 

 of tho '■ oral oriran." 



LIST OF REFERENCE LETTERS, Etc. 



a, b, c, d. Special rows of cells associated with the "oral organ." 



Al. 1 Main central canal. 



AI. 2 Ahoral canal. 



AI. 3 Canals traversing the "ai)i)ral organ." 



B.l.g. Lip of lateral grove. 



Ct. "Cuticle" of mai-ginal h.ind. 



E. Nuclei of special cells for attachment of "aboral organ. 



Gl. 1 Ribbon-like l)and of cells on walls of central cavity. 



Gl. 2 Flattened ceils on walls of centr-al cavity. 



L.g. Lateral grove. 



N. "Neck" of "oral organ." 



0. B. Part of "oral organ" attached to or-al margin." 



O.M. Margin of oral opening. 



P. Proliferating cells. 



Pr. Solid processes of "abor'al organ. ' 



Pet. Punctated material of mai-ginal liand. 



Spt. Faintly marked septum (?). 



