ON THE EDWARDSIA-STAGE OF LEBRUNIA. 269 



The Edwardsia-^tdigQ of the Actinian Lebrunia, and the Forma- 

 tion of the Grastro-coelomic Cavity. By J. E. Dueeden", 

 Assoc. Eoy. Coll. Sci. (London), Curator of the Museum of 

 the Institute of Jamaica. (Communicated by Prof. Howes, 

 Sec.Linn.Soc.) 



[Bead 15th June, 1899.] 

 (Plates 18 & 19.) 



Contents. ^ 



Page 



I. Systematic , 269 



II. External Characters 271 



Development of Tentacles 273 



III. Internal Anatomy and Histology , 276 



1. Ectoderm 278 



2. The Archenteron and Formation of the (Esophagus... 281 



3. Larval Ccelomic Spaces and Formation of the Gastro- 



coelomic Cavity 285 



4. Mesenteries 291 



5. Mesenterial Filaments ,,. 292 



IV. Relations of the Tentacles and Mesenteries 297 



V. Conclusions 300 



VI. BibHography' 311 



DTJEIN& the temporary establishment in November, 1898, of a 

 marine biological laboratory at Bluefields *, Jamaica, in connection 

 with the Institute of Jamaica, several specimens of a Lebrunia 

 were found in the act of extruding larvse. An examination of 

 these, while in the living condition and when sectionized, discloses, 

 amongst other characters, some very exceptional features in the 

 development of the tentacles, and in the formation of the gastro- 

 coelomic cavity of the adult. I am also able to add, by way of 

 comparison, a few facts in connection with the freshly-extruded 

 larvse of Aulactinia stelloides, McMurrich. 



I. Systematic. 

 The specific determination of the first-mentioned Actinian 

 calls for a few remarks. It is a small form which occurs in 



* Bluefields is the name given to a property, formerly a sugar estate, on the 

 south-west coast of Jamaica, rendered classic to local naturalists as the residence 

 of Philip Henry Gosse, F.E.S., during his collecting trip of eighteen months, 

 from 1844-46. The principal features of its natural history, and those of 

 Bluefields Bay, are most vividly portrayed in Gosse's work : ' A Naturalist's 

 Sojourn in Jamaica ' (London, 1851). 



LINN. JOUEN. — zoology, YOL. XXVII. 21 



