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SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 97 



the vertical axis of its base, and this is the usual motion of the 

 appendage; but the latter can also be lifted and depressed, and the 

 up-and-down motion evidently results from an antagonistic action 



Fig. 1 6. — Development, structure, and innervation of the polychaete appendages. 



A, section through larval rudiment of persistent dorsal tentacle (tlR) of 

 trochophore of Lopadorhyuchus (from E. Meyer, 1901). B, transverse sec- 

 tion of larva of Lopadorhyuchus through rudiments of a pair of chaetal sacs 

 (chS) and associated cirri (from Meyer, 1901). C, parapodium of adult Lopa- 

 dorhynchiis. D, structure of the armature of a parapodium of Myzostomutn 

 asteriae Marinzeller, diagrammatic (from Stummer-Traunfels, 1903). E, a 

 myzostomid, ventral view, showing parapodia. F, diagrammatic section of an 

 amphinomid, Hcnnodice canmcnlata Pallas, showing widely separated notopodia 

 (dPd) and neuropodia (vPd) and their innervation (from Storch, 1913). G, 

 section of Nereis virens Sars, showing innervation of parapodia (from Hamaker, 

 1898). 



a, lateral nerve from podial ganglion; Acic, acicula; acmcls, acicular muscles; 

 h, notopodial ganglion; Brn, branchia; c, neuropodial ganglion; Cli, chaeta or 

 chaetae ; chS, chaetal sac ; Coel, coelom ; dCir, dorsal cirrus ; dcR, dorsal cirrus 

 rudiment; dPd, notopodium ; Ecd, ectoderm; Gng, ventral ganglion; m, pri- 

 mary muscle cell ; n, primary neural cell ; NCls, nerve cells ; A''^', nerve ; Papd, 

 parapodium ; PdGng, podial ganglion ; tlR, rudiment of tentacle ; vCir, ventral 

 cirrus ; vcR, ventral cirrus rudiment ; VNC, ventral nerve cord ; vPd, neuro- 

 podium ; 3, dorsal muscles ; 4, ventral muscles. 



between the dorsal and ventral muscles. The intrinsic muscles of the 

 parapodium include protractors and retractors of the chaetal sacs. The 

 principal protractors (B, C, 12, 16) converge from the parapodial 

 walls upon the inner ends of the acicular processes of the sacs (B, 



