144 ACALEPIIS IN GENERAL. Part I. 



When the two highest authorities in the natural history of Corals, Milne- 

 Edwards and Dana, agree in considering the genus Millepora as a member of the 

 class of Polyps, I would not venture to suggest a different view of its affinities, 

 had I not Ijeen able leisurely to examine the animal of that kind of Coral, which 

 had never been observed before, and satisfied myself that it has none of the typical 

 characteristics of the Polyps, neither radiating partitions, nor digestive sac hanging 

 in the mam cavity, while it agrees so closely with the true Hydroids, and especially 

 with the genus Hydractinia, that there can be no doubt left in what direction its 

 natural affinities point. (Compare PI. XV. Figs. 3-13 with PI. XVI., respecting which 

 more will be found in the sequel.) With these tacts before us, Millepora must im- 

 questionably be removed from the class of Polyps and referred to that of the 

 Acalephs, as soon as it is conceded that the Hydroids are Acalephs, and not Polyps. 



RELATIONS ASSIGNED BY MILNE-EDTVARDS TO THE TABULATA AND EUGOSA, ANT) TO 

 SOME OF THE HYDROIDS IN THE CLASS OF POLYPI, 1850-1852. 



1st Sub-class. CORALLAEIA. 



1st Order. Zoanlharia. 



1st Group. Mala codcrmata. Families: Actiuid* ; Actiniiuv, Tlialassianthiua^, Pliyllactina>, 



Zoantliiiuv ; Cerianthid*. ; Miiiyadidie. 

 2d Group. Aporosa. Families: Turbinolida;; Cyathinina;, Turbinolina^ ; Pseudotur binolida; ; 

 OculinidiB ; PseudoculinidiV ; Astrandte ; Eusmilina;, Astr»in:e ; Pseudastreid» ; Fungida; ; 

 Fungina", Lopboserina'. 

 3d Group. Perforata. Families : Madrei)orida\ Euspammida', MadreporiiKP, Turbinaria> ; 



Poritida' ; Poritina^, Alveoporina\ 

 4tli Group. Tabulata. Families: Milloporida- ; Favositidaj : Favositina', Cbanitime, Ilaly- 



sitina^, Pocilloporiiiai : Seriatoporida' ; Thesida\ 

 5tli Group. Tubulosa. Family: Auloporida-. 



Gtli Group. Rugosa. Families : Staurida^ ; Cyatbaxonida^ ; Cyatbopbyllida' : Zapbreutina% 

 Cyatbopbyllida', Axopbyllina^. 

 2d Order. Alcyonaria. Families : Aleyonida^ ; Cornularina-, Telestbiiia", Aleyonina', Tubiporina* ; 



Gorgonidai ; Gorgonina?, Isidina', Coralliina^ ; Peimatulida'. 

 3d Order. Podactinaria. Family : Lueernarida?. 

 2d Sub-class. IIydrakia. Family : Ilydrida'. 



Of these groups I bold that the Zoaniharia, Malacodermata, Aporosa and Perforata, and the Alcy- 

 onaria alone, are genuine Polyps ; and that the Tabulata, Tubulosa, Rugosa, Podactinaria, and Hydraria 

 are Acaleiihs. 



Since, from this time forward, tlie influence of Embryology upon the classifi- 

 cations of Acalephs is more or less distinctly felt, I deem it necessary to introduce 

 here some comparisons between the earlier attempts at a systematic arrangement 

 of these animals and the later systems, in order to render more evident the 

 progress made thus far. 



