ON PENNELLA BALAINOPTER. 433 
Fig. 7. Transverse section through the upper part of the head. The oral cleft on the ventral surface, 
the tubercles and the arrangement of the striped muscles are shown. x13. p. 415. 
Fig. 8. Transverse section through the head below the oral cleft, showing the relation of the alimentary 
canal A. to the midventral and dorsal spaces, the pair of cesophageal ganglia, each of which has a cavity in 
the centre, and the striped muscles. Ch. marks a transversely divided column of chitin, lying in relation to 
the dorsal space. x13. pp. 418, 419. 
Fig. 9. Transverse section through the parasite close to the origin of the arms. The relations of the 
alimentary canal with the ventral and dorsal spaces and the large amount of areolated tissue are shown. 
cao. p. 416. 
Fig. 10. An oblique section through the parasite at the origin of an arm, showing the relations of the 
alimentary canal to the dorsal and ventral spaces, and to a mass of areolated tissue. The position of the 
inner column of chitin, Ch., is also shown. x13. p. 418. 
Fig. 11. Transverse section through the arm close to its origin to show the two large areole and those 
of smaller size. x13. p. 416. 
Fig. 12. Transverse section through the arm about its middle. x13. p. 416. 
Fig. 13. Another transverse section through the arm, in which many of the areole were crowded with 
nuclei, x13. p. 416. 
Fig. 14. Transverse section through the body a short distance below the arms, showing the areolated 
tissue which surrounded the alimentary canal and dorsal and ventral spaces. x13. p. 419. 
Puate III. 
Fig. 15. Section through an cesophageal ganglion, showing the nucleated nerve cells. p. 417. 
Fig. 16. Transverse section through the attenuated thoracic region, showing the alimentary canal and 
the dorsal and ventral spaces. x13. p. 419. 
Fig. 17. Transverse section through the body at the junction of the thoracic and genito-abdominal 
segments. The upper end of the pair of ovaries can be seen at the sides of the alimentary canal, the mucous 
lining of which was torn off in making the section. x13. p. 420. 
Fig. 18. Transverse section through the caudate abdominal segment, showing the relation of the 
alimentary canal to the dorsal and ventral spaces and the origin of one of the pennate bristles. x13. p. 423. 
Fig. 19. Transverse section through the intestine at the anal orifice. On each side of the gut is a pair 
of large transversely striped muscles; on the ventral aspect a pair of non-striped muscles which form a 
sphincter arrangement around the intestine. x50. p. 422. 
Fig. 20, Transverse section through the upper part of the genito-abdominal seyment, showing the two 
ovaries placed dorsally, with a cement and an oviduct on each side of the ventral space, separated from each 
other by an interval ; also the alimentary canal with its foldings or diverticula. x15. p. 423. 
Fig. 21. Transverse section through the same region, showing the same parts, but with a less complicated 
alimentary canal, x 13. 
Fig. 22. Transverse section through the upper part of the genito-abdominal segment, showing ovaries 
and cement glands in the same plane, also oviducts and cement ducts. x15. p. 425. 
Fig. 23, Transverse section through the genito-abdominal segment, showing the pair of cement glands 
at the sides of the. dorsal space; the cement ducts and oviducts are near the ventral space: the walls of 
the ducts on each side are connected by an intermediate band. The pigmented lining membrane has shrunk 
away from the wall of chitin. The alimentary canal is reniform in section. x13. p. 425. 
Puate IV. 
Fig. 24. Section through an ovary, showing the contained ova. p. 424. 
Fig. 25. Transverse section through the lower part of genito-abdominal segment, no ovaries or cement 
glands, but the walls of the oviduct and cement duct on each side are in contact: bundles of striped 
muscles, s.m., are also seen. x13. p. 425, 
Fig. 26, A similar transverse section, showing fusion of the oviduct with the cement duct. x 13. 
Fig. 27. A similar transverse section, where the two ducts on each side are blended, and form a 
receptaculum, A loop-like arrangement across the mesial plane connects the two receptacula. x 13. 
TRANS. ROY. SOC. EDIN. VOL. XLI. PART II. (NO. 18). 64 
