300 J. H. ASH WORTH. 



1889. Wkigiit, E. P., and Studer, T. H. — ' Challenger Reports,' Zoology, 



vol. xxxi, " Alcyonaria," 1889. 

 1895. Bourne, G. C. — "On the Structure aud Affinities of Heliopora 



coerulea, Pallas, with some Observations on the Structure of Xeuia 



aud Heteroxeuia," 'Phil. Trans.,' 1895. 



1895. HiCKSON, S. J. — "The Anatomy of Alcyonium digitatum," ' Quart. 

 Journ. Micr. Sci.,' vol. xxxvii, part 4, 1895. 



1896. SciiENK, A. — ' Clavulariiden, Xeniiden, uud Alcyoniiden von Teruate,' 

 Prankfurt-a.-M., 1896. 



1898. — AsiiwouTH, J. H. — " The Stomodaeum, Mesenterial Pilameiits, and 

 Eudoderm of Xenia," ' Proc. Roy. Soc,' vol. Ixiii, 1898. 



EXPLANATION OF PLATES 23—27, 



Illustrating Dr. J. H. Ashwortli's paper on "The Structure 

 of Xeuia Hicksoni, uov. sp., with some Observations 

 on Heteroxenia Elizabethsej Kolliker." 



List of Reference Letters. 



A, A 3, A 5. Autozooids of Heteroxenia (the numbers refer to the table 

 on p. 287). Cg. Coagulum in central cavity of sperm sac. Cn.C. Cnido- 

 blast cell. L.M. Dorsal mesentery. D.3I.F. Dorsal mesenterial filament. 

 Ed. Ectoderm. Ed. Ch. Chain or cylinder of ectoderm cells round cylinder 

 of denser mesoglcea. Ed. Sir. Strands of ectoderm cells. End. Endoderm. 

 End. Can. Endodermic canals. F. Plagella of siphonoglyph. G. C. Gland- 

 cells in stomodseum. G.F. Giant flagella of endoderm cells. Gen.C. Genital 

 cells in various stages of development. Lo7ig. Can. Longitudinal endodermic 

 canals. L. M. Lateral mesentery. M. Mesentery. Mg. Mesoglcea. Mg. D. 

 Denser cylinder of mesoglcea around each coelenteron in stem. Mo. Mouth. 

 Muc. C. Mucus cells of ectoderm. M. P. Muscle processes of endoderm 

 cells. N. Nucleus. Nem. Nematocysts. N. C. Nerve cells. N. F. Nerve 

 fibrils. R. 31. Retractor muscles in mesenteries. S. S 7. Siphonozooids of 

 Heteroxenia (the number refers to the table on p. 288). Sec. Secretion of 

 gland-cells of stomodseum. Si. Siphonoglyph. Sp. Spicules. Spz. Sper- 

 matozoa. SL Stomodeeum. Sup. Can. Superficial canal. S. S. Sperm sacs. 

 V. M. Ventral mesentery. Z. Zooxaiithellse. 



PLATE 23. 

 Fig. 1. — Vievp of the colony of Xenia Hicksoni. From one of the stems 

 on the left side all the larger polyps have been removed, so that the umbellate 

 summit of the stem, with the young polyps growing round its edge, may be 



