THE ENTEROPNEUSTA. 679 
Fie. 17. Ptychodera viridis. Section through post-branchial groove. x 12. 
Fic. 18. Pt. flava, var. muscula. Section just anterior to the proboscis pores, shewing the expansion 
of the nuchal skeleton over the racemose organ (7). x 45. 
Fie, 19. Pt. viridis. Section through anterior collar region. x 20. 
Fie, 20. Sp. maldivensis, Section through post-branchial groove. x 45. 
PLATE XLIII. 
All figures on this plate are from P¢. flava, var. parva. 
Fig. 21. Through anterior part of proboscis. x 30. 
Fic. 22. Through anterior portion of central proboscis complex. 30. 
Fic. 23. Through specimen in which the two proboscis pores have a common opening near the 
mid-dorsal line. x 54. 
Fig, 24. Through hinder part of proboscis shortly before the lateral diverticula of the stomochord 
appear. x 54. 
Fie. 25. Through region of the lateral diverticula of the stomochord. x 54. 
Fie. 26. Through the proboscis pores behind the lateral diverticula of the stomochord. x 54. 
Fie. 27. Through anterior cavity containing region of collar. x 30. 
Fic. 
to 
ie) 
Through region of racemose organ, behind the proboscis pores. x 54. 
PLATE XLIV. 
Fie. 29. Pt. flava, var. asymmetrica. Section through collar cord. x 45. 
Fie. 30. Pt. flava, var. parva. Section through same level as Pl. XLIII. fig. 25, but through 
another specimen in which the lumen of the stomochord is obliterated instead of being patent. 
x 45, 
Fie. 31. Pt. flava, var. parva. Section through middle of collar region shewing longitudinal muscles 
arranged in bundles. x 20. 
Fic. 32. Pt. flava, var. parva. Section through proboscis pores, In this specimen the perihaemal 
spaces reach forwards to this level. More usually they commence shortly behind the pores 
(cf. Pl. XIII. figs. 23, 26). . x 45. 
Fie. 33. Pt. flava, var. saxicola. Section just anterior to the proboscis pores shewing great width 
of keel of nuchal skeleton. x 45. 
Fic. 34. Pt. flava, var. saxicola. Section through stomochord in region of lateral diverticula. x 85. 
Fies. 35, 36, 37. Pt. flava, var. saxicola. Sections through the pygochord. The three sections are 
from the same specimen; fig. 35 is nearest to the anus, fig. 37 is furthest from it. x 85. 
Fie. 38. Pt. flava, var. saxicola. Through anterior branchial region, x 12. 
Fic. 39. Pt. flava, var. saxicola. Through posterior branchial region of same specimen as in fig. 38. 
x 12. 
Fic. 40. Pt. flava, var. saxicola. Through level immediately behind the post-branchial groove. Also 
from same specimen as fig. 38. x 12. 
Fie. 41. Pt. flava, var. sawicola. Through region of post-branchial groove. The genital pleurae 
are still almost as large as in the branchial region. «x 12. 
87—2 
