LITERATURE OF TIIE SUB-KINGDOM CCELEXTEHATA. 429 



Lueernariada?, as distinct from such of the Crypt ocai'im' as mnv here- 

 after seem worthy of being placed in an ordinal group, to which may 

 be applied the title of Medusida?. 



The position of the Lueernariada' faeing thus defined, a few- 

 words may now he said concerning another group »»•' Cu'lrnteratn, 

 as to tlic nearest affinities of which much needless uueertainl v ami 

 difference of opinion still seems to prevail; namely, the Ctenophora. 

 Many years ago, De Blainville, 53 followed by Quoy et Gaiinai-d,-^ 

 auggested that their true place was in the Molluscous sub-kingdom, 

 of which, in 1S51, Yogt 54 constituted them a class, in close proximity 

 to the Tunicata. But this view of their affinities met with little 

 encouragement. Nevertheless, it contained one slight element of 

 truth, in so far as it denied the close relationship of these animals to 

 the Siphonophora and Discophora, with which most zoologists, mis- 

 led by their transparent gelatinous aspect and free oceanic mode of 

 life, have long continued to associate them. Preferable seems the 

 opinion of Leuckart, J. V. Cams, Gegenbaur, and Sars, who elevate the 

 Ctenophora to the rank of a distinct class of Ccelenterata, equivalent 

 to the Polypi and Hydromedusae. For, in truth, the Ctenophora, as 

 Prey and Leuckart 55 plainly hinted in the year 1847, come nearer to 

 the first of these two classes than to the latter. These writers com- 

 pare the structure of Pleurobrackia with that of Actinia, indicating 

 the existence of some fundamental points of similarity between them. 

 But these excellent suggestions were permitted to remain unheeded 

 until, in 1856, they were restated by Huxley, 56 who, clearly perceiving 

 the strong arguments in favour of such a step, united the Ctenophora 

 and Polypes into one class, to which he gave the name of Actinozoa. 

 A brief anatomical comparison of the genera mentioned above, 

 selected as accessible representatives of the two groups thus brought 

 together, may serve to place in its proper light the intimate nature 

 of the systematic relationship subsisting between them. 



Pirst, on comparing the nutrient systems of Actinia and Pleuro- 

 hrachia^ " the digestive sacs of the two organisms are clearly seen 

 " to correspond ; in form, in relative size, and mode of communication 

 " with the somatic cavity. The funnel and apical canals 58 of Pleuro- 

 " brachia, though more distinctly marked out, are the homologues of 

 " those parts of the general cavity which in Actinia are central in 

 " position, and underlie the free end of the digestive sac. So, also, 



52 Manuel, &c. pp. 143 and 641. 



53 Zoologie, Voyage dc 1' Astrolabe, Tom. 4, p. 3G. 

 51 Zoologischc Briefe, Band I. p. 254. 



55 Beitriige, &c. passim. 



56 Lectures, p. 621, June 21, 1856. 



57 Cydippe of Eschscholtz (1829) and of most subsequent -writers ; but the name 

 Plmrobrachia, proposed by Fleming in 1828, has the priority. 



58 The two short canals opening directly from the funnel. 



