THE ANTHOZOA 



45 



much reduced, have no filaments and no muscle banners (Fig. 

 XXI. 5). Thus we find that whilst twelve primary mesenteries 

 are present, four of these, namely, those which are absent in 

 Edwardsia, lag behind the others in size and importance. 



We are justified, therefore, in regarding the Edwardsiae as 

 the nearest living representatives of the ancestor of the six-rayed 

 Actinians. 



.IV 



II 



L 



Fio. XXI. 



1. Edn'iii-i^iii i-Ji'iinredii, Pane. (After A. Andres.) 



2. Transverse section through the stomodseal region of Edwardsia, showing the eight mesen- 

 teries, and the arrangement of the muscle banners, s, sulcus ; si, sulculus. 



3. Halcampa endrmnitata, Andr. (After A. Andres.) 



4. Transverse section through the stomodieal region of Halcampa, showing twelve couples of 

 pompli'tf primary mesenteries and six couples of minute incomplete mesenteries in the exocoeles. 

 dm, directive mesenteries. 



5. Transverse section of the same species below the region of the stomodaeum, showing six 

 fertile mesenteries I, I ; n, n ; in, in ; the sterile sulcular directives iv, iv, bearing filaments, 

 and the reduced mesenteries, v, v, and vi, vi, of the first cycle. 



To the group of six-rayed Actinians we must now add the 

 large assemblage of forms, both single and colonial, which have 

 hitherto been classed apart as the Madreporaria or stony corals. 

 Researches made by various authors in recent years have shown 

 that the anatomy of a Madreporarian coral, leaving the skeleton 

 out of the question, is in all essential particulars identical with 

 that of such a form as Actinia equina. H. V. Wilson has further 

 shown (98) that in the coral Manicina areolata the sequence of the 

 development of the first six pairs of mesenteries is identical with 

 that of Rhodactis and Halcampa. Such being the case, it is no 



