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R, C. PUNNETT. 
37. Pt. flava, var. muscula, A nearly ripe ¢ gonad breaking through to the ectoderm. 
x 180. (sp=spermatocytes.) From an iron haematoxylin preparation. 
38. Pt. flava, var. laceadivensis. From young specimen. a—e represent stages in the formation 
of the giant nutritive cells. All x 520. 
39. Pt. flava, var. laccadivensis. Young gonad, shewing cavity formed inside, and outer coat 
of nutritive cells forming a kind of follicle. The membrane surrounding the gonad derived 
from the lateral septum is still intact. x 410. 
40. Pt. flava, var. laccadivensis. Young gonad, slightly older than in preceding figure. The 
membrane surrounding the gonad tends to break down in places. «x 410. 
41. Pt. flava, var. saxicola. Section through young gonad with ectodermal connection. At the 
base of the gonad the membrane is deficient permitting the invasion of nutritive cells. x 180. 
42. Pt, flava, var. saxicola. Gonads somewhat older than in preceding figure. x 110. 
PLATE XLI. 
1. Balanoglossus parvulus. Section through branchial region. x 45. 
2. B. parvulus. Through region of post-branchial groove. x 45. 
3. B. parvulus. Through nuchal skeleton in anterior region of collar. x 45, 
4. B. parvulus. Through post-branchial genital region. x 45, 
5 
Spengelia porosa, Through hepatic region. On the right the section has gone through 
the middle of a hepatic caecum. x 12. 
6. Sp. maldivensis, Section through nuchal skeleton in the region of the keel (nk.). The 
perihaemal cavity (ph.) of the right side is seen at this level. That of the left side does 
not reach so far forwards. x 45. 
7. Sp. porosa. Section through the intestinal region behind the hepatic caeca. x 12. 
8. Sp. maldivensis. Schematic longitudinal sagittal section reconstructed from transverse 
sections. x 10. 
9. Willeyia bisuleata. Section through proboscis pore. x 45. 
10. W. biswleata. Schematic reconstruction as in fig. 8. x 10. 
PLATE XLII. 
ll. Spengelia porosa. Section through posterior part of proboscis. x 12. 
12. Willeyia bisuleata. Section through anterior part of proboscis. x 30. 
13. W. bisuleata. Section through branchial region. x 22. 
14. W. bisuleata. Section through genital region. x 22. 
15. Wz. bisulcata. Section through hinder part of anterior neuropore. ~ 45. 
16. W. bisuleata. Through anterior part of anterior neuropore, shewing. the cesophageal nerve 
coming off on the left side of the figure. x 45. 
