2 THE VOYAGE OF H.M.S. CHALLENGER. 



author was acquainted only with the short preliminary notice of my researches published 

 in the Jena Proceedings,' not with the Eeport itself ; a fact easily understood when one 

 considers how long before the date of publication a monograph constructed on such a 

 plan must be completed. In his comprehensive revision of the Actiniae, and re-definition 

 of families and genera, he has been prevented from referring to my contemporaneous 

 attempt at revision, since this first appeared in the detailed Report. As it is most 

 desirable that two systems, appearing within a short time of one another, should be 

 brought into such relation as to avoid future discordance and mistake, I accept with 

 pleasure the opportunity of a critical utterance on their mutual relations. 



As against the six chief divisions into which I divide the Actinise (Hexactinise, 

 Paractinise, Monaulei^, Edwardsise, Cerianthese, Zoanthese), Andres erects seven, viz. 

 Edwardsinfe, Actinium, Stichodactylinse, Thalassiauthinse, Zoanthinse, Cerianthinai, 

 Minyadin£B. With regard to three chief groups we afl^in complete accord (Edwardsia3, 

 Cerian these, Zoanthese), except for the fact that Andres, in my opinion, relies on too 

 inconstant arid unimj^ortant external characters ; while, as I have shown, these groups, 

 at least, admit of anatomical characterisation by the arrangement of their mesenteries, 

 and thus can be far more clearly and sharply circumscribed. If the reader compare in 

 this connection the definitions of the Zoanthese furnished by myself and by Andres, it 

 will be readil)' admitted that none of the characteristics of the latter author, such as 

 colony-formation or incrustation, are constant within the group ; that, on the other 

 hand, all the forms follow one and the same law of mesenterial arrangement, first 

 recognised by G. von Koch. 



If we carry the comparison further, we find that Andres places beside the Actininse, 

 as separate groups, the Thalassianthinae, the Stichodactylinaj, and the Minyadiuse ; 

 though with a certain caution, as having himself studied no representative of them. 

 I believe that he has here exceeded the systematic value which can be safely assigned 

 to the form of the tentacles and their distribution on the mesenterial chambers. 1 have 

 studied certain Stichodactylinaj {Corallimorijhits rigidv^, CoraUmiorphus profundus, 

 and Heterodactyla hempricJiii), and of the Thalassianthinse, ThaJassiantJms aster, 

 and can assert, as the result of a thorough examination of their structure, that in all 

 im^jortant points they agree with the hexamerous Actinise ; nor have I any doubt that 

 these forms, even if united into separate families, must be ranged among the Hexactinise. 

 Finally, the group of Minyadinse has for many reasons, which I entirely recognise, 

 undergone at the hands of Andres so sharp a criticism, that one can hardly see why he 

 retains it, or why at least he does not allow it to rank merely as a subdivision of 

 Hexactinise, until the necessity of its removal from that group is rendered apparent by 

 anatomical investigation. 



From the point of view explained, I am of opinion that all the forms referred to 



1 Jenaiscke Zeilschr., Bd. xv. p. 10, 1881. 



