200 FLOEENCE BUCHANAN. 



cbaetse. cmp. Notopodial "cirrus." crp- Neuropodial cirrus. (The right 

 side of the section is behind the left.) s. s. m. Muscles going to setal sacs. 

 d. V. m. Dorso-ventral muscles, gl. Gland-cell in epidermis. 7ieph. e. Ex- 

 ternal limb of thoracic nephridium. neph. i. Internal limb of thoracic nephri- 

 dium. vase. r. lutra-vascular ridge in d. v. dorsal vessel, v. v. Ventral vessel. 

 d.v.v. Parts of dorso-ventral vessel, n. c. Nerve-cord. _^./. Giant-iibre. 



Fig. 6. — Transverse section of the same worm through the anterior ab- 

 dominal region. The section is taken just in front of a septum, and therefore 

 the intestine does not occupy so much room in section as it otherwise would. 

 The dorsal vessel {d. s. v.) is separated from the intestinal sinus ; the intra- 

 vascular ridge (vase, r.) is very close to but distinct from the wall of the 

 intestine. Other letters as in Fig. 5. 



Fig. 7. — Transverse section of the same specimen through the posterior 

 abdominal region, where the intestine is not constricted intersegmeutally. 

 sifi. Sinus, complete all round the intestine, mes. Dorsal mesentery. 7>ies'. 

 Ventral mesentery. Other letters as in Fig. 5. 



Fig. 8. — Transverse section through another specimen, in which the gonads 

 are developed (stained with borax-carmine), test. Testes, nep/i. Nephridia, 

 seen opening to the exterior on the left-hand side of the figure in ext. A 

 parasite {par.) is seen in the intestine. The section is taken farther back 

 than that represented in Fig. G, and consequently the sinus shows no trace 

 of the dorsal vessel. From the ventral vessel {v. v.) a branch is seen passing 

 off on the right-hand side. Other letters as in Fig. 5. 



Fig. 9. — Transverse section of cephalic tentacle, epid. Ciliated epidermis. 



c. m. Circular muscle layer. I. m. Longitudinal muscle layer, c. ep. Ccelomic 

 epithelium, ccel. Coelora (containing ccelomic corpuscles in the living), t. v. 

 Vessel of tentacle. 



Fig, 10. — Transverse section of branchia. d. br. v. Branchial vessel in 

 connection with dorsal vessel, v. br. v. Branchial vessel in connection with 

 ventral vessel, ccel. Coelom. Other letters as in Fig. 9. 



Fig. 11. — Dorsal view of the posterior extremity of the body of a speci- 

 men in which the ciliated ridges could be seen in the intestine {int.), just in 

 front of the anus {a.). 



Fig. 12. — Serai-diagrammatic dorsal view of the head to show the probable 

 arrangement of vessels. Pro. Prostomium. iiip^. Notopodial chaittc of 1st 

 segment, nrp^. Neuropodial chfetse of 1st segment (with " cirrus "). d. c. 

 Dorsal collar (notopodial " cirri ") of 2ud segment. d. v. Dorsal vessel. 



d. br. V. Branchial vessel in connection with dorsal vessel, v. br. v. Branchial 

 vessel in connection with ventral vessel, v. v. Ventral vessel, i. v. Vessel 

 of cephalic tentacle, d. v. v. Coiled dorso-ventral vessel. 



F'lG. 13. — Parasite from intestine (Monocystis hekaterobrauchii). 

 vac. Vacuole, n. Nucleus. 



Fig. 11.— Abdominal nephridium. cvi. Its external opening. 



