N'OV 4 1899 



THE STRUCTURE OF XENIA HICKSONl. 245 



The Structure of Xenia Hicksoni, nov. sp., 

 with some Observations on Heteroxenia 

 Elizabethae, Kolliker. 



By 



J. H. Asliwoitli, D.Sc.(L,oiid.)i 



Demonstrator in Zoology, Owens College, Manchester. 



With Plates 23—27. 



Contents. 



PAGE 



Introduction ........ 246 



External Characters of the Colony : Polyps, Tentacles, Pinnules . 246 



Diagnosis of the Species Xenia Hicksoni .... 249 

 General Anatomy : Stomodseum and Mesenterial Filaments ; Coelentera 



of Polyps ; Mesogloea, its Canals and Cells . . . 251 



Ectoderm: Neraatocysts, Spicules ..... 257 



Mesenteries : Mesenieiial Filaments, Cells in Mesoglcea of Mesenteries 262 

 Endoderm : Giant Flagella . . . . . .264 



Mesoglcea; Superficial and Internal Canal Systems; Cells in Mesoglcea 267 



Spermatogenesis ....... 274 



Nervous System ....... 277 



History of our Knowledge of the Buds of the Xeuiidse . . 278 



External Characters of the Buds of Xenia Hicksoni . , . 282 

 External Characters of Heteroxenia Elizabethte: of its young 



Polyps and of its Siphonozooids ..... 284 



Internal Anatomy of Heteroxenia, Autozooids, Siphonozooids, Stem 289 



Origin and Internal Structure of the Buds of Xenia Hicksoni . 291 



General Summary ....... 297 



Literature ........ 299 



VOL. 42, PART 3. NEW SERIES. E 



