244 EDWIN S. GOODRICH. 



EXPLANATION OF PLATES 15 & 16, 



Illustrating Mr. Edwin S. Goodrich's paper "Notes on the 



Anatonay of Sternaspis/' 



List of Reference Letters. 



a. Anus. ll.v. Blood-vessel. br. Branchiae. ch. Cheetse. cil. Cilia. 

 cil. epith. Ciliated epithelium. cil. fun. Ciliated funnel. cil. mb. Ciliated 

 membrane, cil. ri. Ciliated ridge, coel. epith. Ccelomic epithelium, d. a. 

 Dorsal area. d. rect. m. Dorsal rectal muscles, d. retr. Dorsal retractors. 

 exir. Extremity of the nephridium attached to the body-wall. gen. d. Genital 

 duct. gen. p. Genital papilla, gr. Granule, int. gr. Intersegmental groove. 

 kit. retr. Lateral retractors, lat. m. Lateral muscle, lat. par. Lateral para- 

 podium. /«^. v. Lateral vessel. ^. ^e«. 5. Lobes of the genital sac. long.m. 

 Longitudinal muscles, lu. can. Lumen of the canal leading from the body- 

 cavity to the cavity of the genital sac. m. Mouth, n. Nucleus, n.c. Nerve- 

 cord. 7ieph. Nephridium. o. cut. Outer layer of cuticle, op. Opening lead- 

 ing into the genital sac. ov. Ovum. ph. Pharynx. post. ch. Posterior 

 chsetae. prost. Prostomium. protr. protractors, rect. Rectum, retr. Re- 

 tractors, retr. lat. ch. Retractors of lateral chaetse. sit. p. Siliceous particles. 

 sph. Transparent sphere, st. Stalk of nephridium. v. a. Ventral area. 

 V. rect. m. Ventral rectal muscles, v. retr. Ventral retractors, v. v. Ventral 

 vessel, w. gen. d. Wall of genital duct. w. gen. s. Wall of genital sac. 



PLATE 15. 



Fig. 1. — Somewhat diagrammatic enlarged view of the genital sac and 

 ducts of Sternaspis dissected out, and viewed from the ventral surface, 

 showing the openings leading from the body-cavity into the genital sac. 

 On the right side the blood-vessel which accompanies the duct is not 

 represented. 



Figs. 2 — 8. — Series of transverse sections through the base of the genital 

 sac and origin of the ducts, showing the communication with the coelom by 

 means of the narrow canal formed by the folding of the ciliated membrane, 

 X 400, cam. 



Fig. 9. — Inner surface of a piece of the ciliated epithelium lining of the 

 genital sac, drawn from the fresh and stained tissue, x about 400. 



Fig. 10. — Outer surface of a piece of the wall of the genital sac, stained 

 with silver nitrate and carmine. The ccelomic epithelium has been partially 

 torn off, exposing the inner ciliated epithelium, x about 400. 



Fig. 11. — General enlarged dorsal view of the nephridia, showing the 

 slender stalk inserted into the body-wall and the small ciliated funnel. 



