ME. J. E. DUEEDEN ON STICHODACTTLIlSr^. 635 



On the Eelations of certain Stichodactylince to the Madreporaria. 

 By J. E. DuERDEx, A.E.C.Sc. (Lond.). (Communicated by- 

 Prof. Gr. B. Howes, F.E.S., Sec.L.S.) 



[Eead 16th June, 1898.] 



That a close relationsiiip exists between the Zoantharian polyps 

 with only a soft body — Actiniaria — and the Zoantharian polyps 

 which form a calcareous skeleton — Madreporaria — has long been 

 recognized. The grounds of resemblance are the general simi- 

 larity in the number, arrangement, and order of development of 

 the tentacles and mesenteries, and the plan of the mesenterial 

 musculature, all features of fundamental importance in Actinozoan 

 morphology. 



Up to the present, however, no more than these general 

 relationships have been established, and systematists have sepa- 

 rated the anemones from the coral-forming polyps, though, as 

 researches have been extended, with more and more of a note of 

 warning that they may ultimately be shown to constitute but a 

 single group. 



Thus Prof. P.. Hertwig (1882, p. 20) , referring to his definition 

 of the Actiniaria or Malacodermata in the ' Challenger ' Peport, 

 observes : " I have included the want of a skeleton in the diag- 

 nosis, and therefore separated the Actiniae from the Corals, for 

 practical reasons ; the division is not a natural one." And 

 further : " Most corals will doubtless be placed later on with the 

 SexactinicB ; perhaps a natural division into forms having a 

 skeleton and forms without skeleton may not be possible, as even 

 the closer limitation of the SexactinicB given here does not 

 exclude the possibility of many of their families having more 

 affinity to single families of corals than to other Hexactinice." 



Commenting upon the same subject, nearly ten years later, 

 Prof. McMurrich (1891, p. 155), in his " Phylogeny of the 

 Actinozoa," remarks : — " I believe that one will not err very much 

 in regard to the relationships of the Madreporaria in accepting 

 the statement of P. Hertwig. . . . The observations which have 

 been recorded since the publication of Hertwig's paper only tend 

 to confirm his opinion. The arrangement of the mesenteries, 

 and their order of appearance, demonstrate conclusively that the 



