76 CEYLON PEARL OYSTER REPORT. 



Fig. 8. Transverse section through the left mantle lobe and both ctenidia, to show their relations and 



the extent of the median (M.c.j.) and lateral (L.C.j.) ciliated junctions. x 15. 

 9. The median ciliated junction between the inner lamella? of the inner gills; org., slight organic 



connection. x 400. 

 ,, 10. The lateral ciliated junction between the outer lamella of the outer gill (;/./.) and the mantle 



lobe (Fall.) x 400. 

 ,, 11. ' Longitudinal section along the gill filaments, to show the ciliated discs (c.d.). x 50. 

 12. Horizontal section across the two ctenidia (four "gills," o.g. and i.g.), to show the plication, the 



interlamellar junctions (i.l.j.), and the principal filaments (/>./.). x 50. 

 ,, 13. Small part of such a horizontal section more highly magnified, to show a principal filament 



(p.f.), several ordinary filaments (;/./.), and an interlamellar junction ('.//.). x 400. 

 14. An ordinary gill filament in transverse section, to show cilia, &c. x 500. 

 ,, 15. Transverse section of a filament at the level of a ciliated disc (c.d.). x 500. 

 ,, 16. Section showing filaments joined by organic union at the level of the ciliated discs, a is an 



ordinary filament free ; b is a filament with a ciliated junction ; c, d, e show ciliated and 



organic junctions together ; / shows a ciliated junction alone. x 400. 

 17. Another group of two filaments showing organic union, x 400. 



PLATE IX. 



Fig. 1. Section through visceral mass, to show stomach (St.), caeca and ducts of digestive gland (D.gl.), 



gonad (Go.), &c. P. shows an encysted Cestode larva, x 20. 



,, 2. Another section of the stomach and digestive gland more highly magnified, x 50. 



3. Duct of digestive gland terminating in caeca, x 50. 



4. Transverse section of caecum of digestive gland. x 400. 



5. Transverse section of pallial muscle bundle enclosing branch of pallial nerve (..). x 400. 



6. Transverse section of rectal ridge (B.r.), showing rectum (Int.Z), posterior aorta (Ao.p.), and 



loose connective-tissue. x 50. 



7. Section across another part of rectal ridge further back. x 50. 



,, 8. Part of transverse section of rectum more highly magnified, to show epithelium. x 400. 



,, 9. Part of wall of stomach highly magnified, to show epithelium. x 400. 



,, 10. Transverse section of intestine near the loop, to show irregular typhlosole. x 50. 



11. Section across labial palps. x 50. 



12. Part of wall of heart, to show striped muscle fibres of the ventricle, x 400. 



13. Part of wall of auricle, to show gland cells. x 400. 



,, 14. Section through ventral end of pericardium, to show pericardial glands. x 50. A, a part moro 



highly magnified, x 400. 



,, 15. Section from glandular part of nephridium, to show renal cells. x 400. 



,, 16. Transverse section of pedal ganglionic mass. x 50. 



., 16a. Another section showing junction of cerebro-pedal connectives. x 50. 



,, 17. Pallial sense-organ. x 50. A, the apex more highly magnified, x 400. 



18. Section showing parieto-splanchnic ganglion and osphradium. x 50. 



,, 19. Sensory papilla on pallial tentacle. x 500. 



20. Tip of velar papilla. x 500. 



,, 21. Section through female gonad, to show developing ova. x 400. 



,, 22. Section through male gonad, to show tubules filled with developing spermatozoa. x 100. 



A, part of a ca?cum more highly magnified. x 400. 



