NEW ENGLISH GENUS OF AQUATIO OLIGOOH^TA. 177 



Fig. 7- — Longitudinal section through three Somites, XT, xii, xiii, in order 

 to show the perienteric blood-sinus. Only structures occurring in the middle 

 line are shown, and no detail is intended. The figure is sufficiently explained 

 on the plate. 



Fig. 8. — A diagrammatic transverse section in the posterior region of the 

 body. On the left side a septum is represented, on the right the coelom is 

 almost filled by the nephridiura. apert. Apertures in the septum for the 

 passage of the tegumentary vessels, which originate from the median trunks 

 immediately in front of the septum, and pass through the septum to be dis- 

 tributed to the somite behind. B. ves. Dorsal trunk. Dors. teg. v. The 

 dorsal tegumentary vessel : that part lying in front of the septum is trans- 

 versely shaded. Int. Intestine, with its perienteric blood-sinus. I. ch. Lateral 

 chaetae. Neph. Nephridium. ne. d. Wide tube of the nephridium perforating 

 the body-wall. ne. p. Nephridiopore. ne. v. The branch from the tegumen- 

 tary vessel to the nephridium. Vent. teg. v. Ventral tegumentary vessel : its 

 portion lying in front of the septum is outlined by dots. V. v. Ventral 

 vessel. 



Fig. 9. — Diagrammatic transverse section through one of the anterior 

 somites. The figure is sufficiently explained on the plate. On the left side, 

 the dorsal and ventral longitudinal tegumentary vessels are shown simply cut 

 across; on the right side, the branches from them to the body-wall are 

 indicated. As in other figures, that connected with this ventral vessel is 

 merely outlined, the other being solid. 



Fig. 10. — A diagrammatic view of four posterior somites : the worm has 

 been opened along the left side, the body-wall on this side being depressed ; 

 the arrow points to the anterior end of the preparation. The tegumentary 

 vessels are here represented in their true relation to the septa, which they 

 perforate. One nephridium {neph.) is outlined, and its funnel {ne.f.) indicated. 

 ne. V. is a cut nephridial vessel. 



Fig. 11. — A general view of the generative organs. To some extent it is 

 diagrammatic, in that the chsetse and the sperm -duct are shown as if the 

 body-wall were transparent. In the last three somites, too, the nephri- 

 diopores are shown {ne. p.). oil. ros. The two pairs of ciliated rosettes, clitell. 

 The extent of the clitellum. Epid. The post-septal coiled part of the sperm- 

 duct, the epididymis, lat. ch. Lateral chsetse. ov. Ovary, ov. d. Oviduct, 

 the funnel of which is shown bending into the ovisac, sp. sac. Sperm-sac. 

 sp. d. Sperm-duct, which lies in the body -wall (see Fig. 19). sp.p. Spermi- 

 ducal pore. spth. Spermatheca. t. Testis, vent. ch. Ventral chsetse. 



Fig. 12. — A longitudinal median section through the anterior end of a 

 specimen in which the buccal region is withdrawn, with the exception of a 

 small portion {a — a!) of the upper lip. cer.g. Cerebral ganglion. N. c. 

 Nerve-cord, prost. Prostomium. Pit. Prostomial pit. sac. Dorsal sac of 



