176 CEYLON PEARL OYSTER REPORT. 



Fig. 1). View of a section through the supra-oesophageal ganglion of the same showing e., the eye. 

 Highly magnified. 



Fig. 10. Transverse section through the introvert partly retracted, showing the small group of grooved 

 tentacles and the rows of chitinized spines. Highly magnified, r., body-cavity, the 

 isolated portion of this space runs up between the ventral retractors and soon disappears, as 

 the four retractors fuse to form the muscular sheath in. round the head ; n.r. nerve cord, 

 which, owing to the retraction of the introvert, is bent, and thus cut across twice; p., papillae 

 on the lower part of introvert ; s.p., chitinized spines round the base of the head ; 

 /., transverse sections of tentacles. 



Fig. 11. A Hrteropsarninia michelini, Ed. and EL, broken across transversely, showing the head end to the 

 left, and the tail end to the right of an Aspidosiphon corallicola, Shut, x 2. 



Fig. 12. Another specimen of the same, fractured longitudinally. The head end of the Aspidosiphon is 

 above. The coral shows three pores on its side which communicate with the coiled tube in 

 which the Gephyrean lives. 



