LIST OK REFERENCE-LETTERS. 



p.p. proboscis-pore. 



pr. I. primary lamella of coenoecium. 



prob. St. proboscis-stalk. 



pst. peristome. 



//. peritoneum. 



p. V. posterior vessel of stalk. 



p.v^ its termination on the alimentary canal. 



r. rectum. 



R. I — 6. right arms. 



R. a. right arm. 



rec. recess into which oviduct opens. 



J. '/j septum between proboscis and collar. 



s. -/g septum between collar and metasome. 



sec. I. secondary lamella of coenoecium. 



s. 0. sense-organ of embryo. 



sp. mass of spermatozoa. 



St. stalk. 



stom. stomach. 



stom."^ second stomach. 



t. testis. 



tent, tentacles. 



/. /. left testis. 



/. ;-. right testis. 



/. V. vessel of testis. 



u. I. upper lip. 



vac. vacuolated ectoderm of embryo. 



V. inv. ventral invagination of embryo. 



V. III. vitelline membrane. 



V. ines."^ ventral mesentery of collar. 



V. iiies.^ ventral mesentery of metasome. 



V. t. ventral thickening of embryo. 



X. problematical tissue of collar-canal. 



y. thickening of ectoderm near anus. 



yk. yolk. 



yk. a. its anterior subdivision. 



z. zooid. 



