430 EEVIEWS. 



" the paragastric 59 and radial 60 canals may be likened to those lateral 

 " portions of the somatic cavity of Actinia which are not included 

 " between the mesenteries. Lastly, the ctenophoral 61 canals of 

 " Pleurohrachia and the somatic chambers of Actinia appear to be 

 " truly homologous, the chief difference between the two forms being 

 " that, while in the latter the body-chambers are wide and separated 

 " by very thin partitions, they are in Pleurobracliia reduced to the 

 " condition of tubes ; the mesenteries which intervene becoming very 

 " thick and gelatinous, so as to constitute, indeed, the principal bulk 

 " of the body." 62 Between the tentacles of Actinia and Pleurobrachia 

 there exist, as Professor Huxley has stated, no greater differences 

 than those which distinguish the same organs in Diphyes and Hydra : 

 moreover, in some Ctenophora tentacles are absent. 



The oceanic habit of the Ctenophora may be paralleled in certain 

 genera of Zoantharia closely allied to Actinia, while their apical 

 canals are to some extent represented by the posterior somatic open- 

 ing in Peachia and JPhilomedusa, or even by the multiple pores of 

 CoraUium. The prolongation of the somatic cavity into a number of 

 tubes is seen in several Alcyonaria, with which order the Ctenophora 

 further correspond in the numerical proportion of their parts. The 

 Ctenophora may, therefore, fairly be viewed as an ordinal group of 

 Actinozoa, from the other members of which class their curious loco- 

 motive bands, thick gelatinous outer layer, nervous system and organ 

 of sense, readily serve to distinguish them. 



If the view here taken of the systematic position of the Cteno- 

 phora be accepted, all Coelenterate forms admit of being arranged 

 under two classes, of which one is equivalent to the Hydromedusa> 

 of Vogt, together with the Lucernariada?, while in the other may be 

 placed the true Actinoid polypes (Zoantharia and Alcyonaria) and 

 the Ctenophora. Eor the first of these groups, the name Hydrozoa, 

 as suggested by Mr. Huxley, 63 seems preferable in many ways to the 

 terms Hydromedusae or Hydroidea, which some have endeavoured 

 to establish in its stead. For the second class, the parallel designation 

 of Actinozoa, 64 proposed by the same writer, may with equal pro- 

 prietv be adopted. 

 — — 



59 The two canals which, issuing from the funnel, run parallel to the sides of 

 the digestive sac. 



60 The canals which, with their branches, serve to connect the funnel and the 

 ctenophoral vessels, next mentioned. 



61 The eight longitudinal canals whose courses coincide with those of the eight 

 rows of locomotive combs. 



62 Greene, op. s. cit. p. 146. 



63 Lectures, sup. cit. Kymer Jones, in 1847, restricts this term to a sub-class 

 containing only the genus Hydra ; in 1855, he extends it so as to include in one 

 group all the Acalephse of Eschscholtz, together witli the Hydrozoa of Owen. 



64 Bronn, op. s. cit. applies this name to all the Radiata ( Ccelenterata Echino- 

 dermata), following De Blainville, who used the same term in a somewhat similar 

 signification. 



