THE STEUOTUBE OF XENlA HICKSONI. 299 



10. A complete series of developing polyps is described, 

 beginning with very young specimens, in which the tentacles 

 are devoid of pinnules, and ending with the adult polyps with 

 multi-pinnuled tentacles. 



11. A similar series of polyps of Heteroxenia Eliza- 

 bethse is described and compared with the siphouozooids of 

 the same colony. It is concluded that Heteroxenia is un- 

 doubtedly dimorphic, as stated by Kolliker and Bourne. 



12. The origin of the buds of Xenia Hicksoni from the 

 superficial canal system, their subsequent growth, and the 

 appearance in them of the mouth, stomodaeum, siphonoglyph, 

 gland cells in stomodseum, mesenteries, dorsal mesenterial 

 filaments, and flagella of the endoderm cells, are traced. It 

 is remarkable that the sexual cells are already differentiated in 

 a young polyp '95 mm. long. 



Literature. 



1833. QuoY ET Gaimard. — 'Voyage de I'Astiolabe,' tome iv, " Zoologie," 



Paris, 1833. 

 1874. Kolliker, A. — "Heteroxenia," 'Festschrift der Piijsical.-Med. 



Gesellschaft iu Wiirzburg,' p. 13, 1874. 

 187G. MosELEY, H. N. — "On the Structure of a Species of Millepora 



occurring at Tahiti, Society Islands," 'Phil. Trans.,' vol. clxvii, part 



i, 1876. 

 1877. Klunzinger, C. B. — ' Die Korallthiere des Rothen Meeres,' erster 



Theil, "Die Alcyouarien und Maiacodermen," Berlin, 1877. 

 1881. MosELEY, H. N. — ' Challenger Reports,' Zoology, vol. ii, Corals, 



1881 (Heliopora and Sarcophy ton). 

 1883. HiCKsoN, S. J.— "On the Ciliated Groove (Siphonoglyphe) in the 



Stomodseum of the Alcyonariaus," ' Phil. Trans.,' part iii, 1883. 



1883. Wilson, E. B.— "The Development of Renilla," 'Phil. Trans.,' part 



iii, 1883. 



1884. Wilson, E. B.— "The Mesenterial Filaments of the Alcyonaria," 



' Mitt. Zool. Stat. Neapel,' v, 1884. 



1887. Haacke, W. — " Zur Physiologic der Anthozoen," ' Zoologischer 

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