480 Scientific Proceedings, Royal Dublin Society. 



Edwardsise, and Alcyonaria exhibit three different ways in which 

 the eight mesenteries may be disposed. They regarded the mesen- 

 teries as symmetrical — i.e. four dorsal and four ventral in the 

 Actinidse, as six dorsal and two ventral in the Edwardsise, while 

 in the Alcyonaria all the eight mesenteries are dorsal. 



Although my observations are incomplete, I have thought it 

 desirable to place them on record, as it may be some time before I 

 am able to discuss the question at greater length. For the present, 

 we may assert that, although the adult Halcampa closely re- 

 sembles the ordinary Actiniae in the ratio of its tentacles, and the 

 disposition of its mesenteries, the larval form is undoubtedly more 

 nearly related to the Edwardsise. 



EXPLANATION OF PLATE XI. 



(Figs. 6-14 are purely diagrammatic.) 



Fig. 1. — Thaumantias globosa, Forbes (Phialidium variable, Haeckel), 

 with parasitic Halcampa ; nat. size. 



2. — The same ; magnified 4 diameters. 



3, — Parasitic larva of Halcampa chrysantliellum, older than that 

 of fig. 1 ; magnified 5 diameters. 



4. — Oral disc of a still older larva, with eight tentacles, but 

 twelve mesenteries, and showing the siphonoglyphe. 



5. — Oral aspect of larva with extended mesenteries ; about 5 

 diameters. 



6. — Transverse section of larval Halcampa through the middle of 

 the oesophagus (stomodaaum). 



7. — Transverse section of .larval Halcampa through the lower 

 portion of the oesophagus (stomodseum). 



8. — Transverse section of larval Halcampa immediately below 

 oesophagus (stomodseum). 



