26 S CEYLON PEAEL OYSTER REPORT. 



PLATE III. 



Fie. 17. Sclerophytwm gardineri. Transverse section through a ventral mesentery bearing a typical 

 Alcyonarian ovum, x 930. Cam. luc. 



Fig. 18. Sclerophytwm gardineri. Transverse section showing the unusual occurrence of two young ova 

 on a dorsal mesentery, x 930. Cam. Inc. 



Fig. 19. Lobophytwm pauciflorwn. Transverse section through a siphonozooid just below the surface. 

 All the columnar cells lining the stomodseum are ciliated, but those of the siphonoglyph are more closely 

 packed and have very long flagella. The endoderm is greatly distorted owing to the presence of 

 zoochlorellae. x 80. 



Fig. 20. Sclerophytwm damim. Longitudinal section showing stages in development of siphonozooids, 

 Sii, Si 2 , Si 3 , by budding. Sii is the youngest and is formed as a bud from the endodermal canal leading 

 from Si 3 , and by an aggregation of ectodermal cells to form the stomodseum, which in the section consists 

 at this stage of only two cells. A plug of mesoglcea at this stage closes the mouth aperture. Si 2 is an 

 older bud. The development of the stomodseum has advanced, but the mouth aperture is still closed. 

 6"i 3 is a siphonozooid which has attained its normal development in this species. The mouth aperture is 

 present and a very rudimentary mesentery (in.) is seen on the right, x 600. 



Fig. 21. Sclerophytwm densum. Longitudinal section through a developing autozooid. The mesenteries 

 are fairly well developed before the mouth aperture and tentacles are formed. Only one mesentery is 

 indicated in the drawing, x 360. 



Fig. 22. Lobophytwm pauciflorwn. Transverse section showing the ciliated communication between two 

 siphonozooids. The endoderm cells differ from those lining the cculeiiteron in that they are long, columnar, 

 and are provided with fairly long cilia, x 600. 



Fig. 23. Sclerophytmn densum. Drawing showing the formation of an endodermal canal by the splitting 

 of a solid cord of cells, x 700. 



