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



The more recent naturalists who have given systematic surveys of the Actinias, and 

 among them Fischer, Jourdan, Klunzinger (Korallthiere des rothen Meeres, Heft, i.), 

 and above all Verrill (Proc. Elliot Soc, vi., Comm., p. 69), sometimes follow Milne- 

 Edwards more closely, sometimes Gosse ; none of them have brought forward new or 

 comprehensive points of view. 



Although the existing systems of the Actinias undeniably recpiire a complete re- 

 modelling on a new foundation, I have refrained from this at present, as the material 

 investigated by me was insufficient. I only considered it absolutely needful to form some 

 larger divisions anew, in order to express in some measure the conditions of relation- 

 ship among the forms. I have taken the structure and arrangement of the septa as 

 the fundamental principle, and distinguish six tribes of Actiniaria : (1) Hexactiniae, 

 (2)Paractinia3, (3) Monauleae, (4) Edwardsiae, (5) Zoantheae, (6) Cerianthese. 



I have followed Gosse as far as possible in fixing the limits of the families, but my 

 great endeavour has been to define more sharply the meaningless characteristics hitherto 

 in use, by bringing more emphatically forward the anatomical characteristics predomin- 

 antly developed in the sej)arate families, such, for example, as the nature of the septa and 

 of the circular muscle, the presence of secondary tentacles and acontia (the latter may 

 appropriately replace the cinclides), and the distribution of the reproductive organs. 

 Thus, I have characterised the family of the Sagartidee afresh, as I have laid down 

 as essential that they should possess acontia and a mesodermal circular muscle, and 

 that the six pairs of principal septa should be distinguished from the rest by being 

 alone perfect, and not bearing reproductive organs. I found these conditions in a 

 whole series of forms belonging to the Sagartice, and if other species hitherto placed 

 among them do not agree in these respects, it is impossible that they should remain in 

 one and the same family. 



As regards the definition of the species, I found myself in a difficult position. All the 

 specimens of the Challenger material before me were in a strongly contracted condition, 

 so that I could only form a very imperfect idea of their natural shape. Many of them 

 were, moreover, injured in being detached from the underlying substance or by the 

 dredging apparatus. The colour had gone entirely, almost without exception, and the 

 only information on this point was that given by Moseley about the few forms described 

 by him in the Transactions of the Linnean Society. Thus, nearly all the characteristics 

 on which former authors based their diagnoses of species were wanting. Verrill, who 

 has a most comprehensive systematic knowledge of Actiniae, declares that in such a 

 case all specimens only knowm in a preserved condition are scientifically of no use ; he 

 has therefore laid down as a fundamental principle, that only living forms, or those from 

 which drawings have been taken in a living condition, can be utilised for accurate 

 systematic description. 



From this point of view, the Challenger material would have been, on the whole, of 



