LITERATURE OF THE SUB-KINGDOM C(ELENTEBATA, 



423 



The arrangements of Eapp, Ehrenberg, Owen and Dana are com- 

 pared in the following table : — 



POLYPI. ZOOPHYTA. 



Bapp, 1S29. Ehrenberg, 1836. Owen, 1843. Dana, 1846. 



Section 1. Class. Class. Order I. 



Exoarii. = Dimorphoea. = Hydrozoa. = Hydroidea. 

 Section 2. Class. Class. Order 2. 



Endoarii. = Anthozoa. = Anthozoa. = Actinoidea. 



Tims diminished in extent, the class Anthozoa has since been 

 adopted by more than one writer, and answers to the group so termed 

 by J. Y. Cams and Kolliker ; 34 to the class Polypi in the systems of 

 Yogt, G-egenbaur, Agassiz and others j and to the recently established 

 class Coralliaria of Milne Edwards. 



The Hydrozoa, on the other hand, have been enriched by the ad- 

 dition of all, or nearly all, the forms included under the Acalephse of 

 Eschscholtz and Cuvier ; the Discophora and Siphonophora of the 

 last mentioned writer being now no longer separable, as members of 

 a distinct class, from the fixed Hydrozoa (CorynidsB and Sertularidse), 

 which in structure they have been proved to resemble. 



The removal of the Discophorous Acalephas to the class Hydrozoa 

 may be viewed as the chief systematic result of the researches of 

 numerous observers on the so-called phenomena of " alternate genera- 

 tion," as occurring among Coelenterate forms. 



Eirst, it has been shown by Sars, Siebold, Steenstrup, Reid, Dal- 

 yell, Desor, Yan Beneden, and others that the ova of Aurelia, 

 Cyanea and Chrysaora, three of the best known and most widely 

 distributed genera of Phanerocarpae, become developed into fixed 

 polype-like organisms, or " Hydra-tubse ;" these, in their turn, by 

 transverse fission, producing a succession of free floating forms 

 similar to those which gave them birth, and which, under the vulgar 

 name of jelly-fishes, are familiar, in outward appearance, to almost 

 every sea-side resident. These investigations, it must be admitted, 

 refer only to the Monostome family of the Phanerocarpae. But 



34 The Coelenterata and Rryozoa are by Kolliker retained in one division, named 

 Radiata Molluscoidea, (as distinguished "from R. Echinodennata), and arranged 

 under six groups, as follows : — 



First group: Hydroidea. — Divided into H. sessilia (= Hydra) and H. nech- 

 alea, (including all the Siphonophora except the Velelliche, which are doubtful). 



Second group: Hydromedusida. — Here are placed the Corynidre, Sertularidae, 

 Yelellidas, (?) and Cryptocarpse. 



Third group: Discophora. — (= Phancrocarpse.) 



Fourth group: Ctenopiiora. 



Fifth group : Anthozoa. 



Sixth group: Bryozoa. 



Vid. p. 77, of Kolliker's "Die Schwimmpolypen oder Siphonophorcn von Mes- 

 sina," 1853. 



VOL. I.— ^. H. B. 3 I 



