

AGASSIZ. NATURAL HISTORY OF THE UNITED STATES. 139 



present Monograph, it is not necessary Hint we should stay to notice 

 them. Turning to the Acaleplue, we lind. first, an order Ctennphora? 

 equivalent to the group so termed by E srlisclmltz. The second order, 

 Discophoras corresponding to the Plianerorarpa' ol' t lie same writer, 

 has been adopted, as such, from Kolliker. The third order, Ilydroida-, 

 includes not only the forms so termed by .Johnston, bu1 likewise the 

 Cn ptorarpa* and Siphonophora of Eschscholtz, together with the 

 genus Lucernaria. The sub-divisions oRhc class Polypi require here 

 no comment. 



In regarding the Ctenophora? as a group of equal import ancc to 

 the Diseophora?, Professor Agassiz expresses his dissent from the 

 views of Milne Edwards, one of the most eminent among original 

 investigators of this group, which, nevertheless, in his recent arrange- 

 ment of the Acalephs, occupies a somewhat subordinate position. 

 So that the opinion of Professor Agassiz on the systematic value of 

 the Ctenophora? may be viewed as intermediate between that of the 

 French, naturalist, and those who, like Leuckart, Gregenbaur, and 

 Sars, would consider these animals as a distinct class of Ccelenterata. 

 In the Section on ' Gradation among Acalephs' it is added that " the 

 Ctenophora?, as the highest order in the class of Acalephs, correspond 

 to the Echinoderms, and especially to the Holothurioids, the 

 highest order of the highest class among Radiates." In a previous 

 Section, Professor Agassiz contends against the recommendation of 

 Quoy and Vogt, to remove these organisms to the sub-kingdom 

 Mollusca. But the close affinity of the Ctenophora? to the true 

 Polypes, as suggested in 1847 by Erey and Leuckart, is not thought 

 worthy of detailed discussion. 



The recognition of the Phanerocarpa? as a separate order cannot 

 but be received with satisfaction by those who, like ourselves, have 

 sought duly to estimate the essential nature of the characters which 

 distinguish these forms from the Cryptocarpa?. Such characters, 

 for the most part purely morphological, would hold equally good 

 even if those singular genetic phenomena, which unite together many 

 of the Cryptocarpa? and the Hydroids, yet remained to be discovered. 



"With pleasure, also, we find Professor Agassiz supporting the 

 opinion that Lucernaria is not a true polype, but rather, allied to 

 the Acalepha?. He places the genus in his third order, Hydroida\ 

 But its nearer relationship to the Phanerocarpa? does not altogether 

 escape his notice, for he expressly adds that "their resemblance to 

 the young Medusa? is very great, especially during the incipient stage 

 of their Strobila state of development." 



The last order of Acalepha? in the system (^ Professor Agassiz 

 forms a group of very considerable extent, in our opinion of more 

 than ordinal value. In addition to the genus Hydra, the fixed 

 Hydrozoa, the Siphonophora, the Cryptocarpa?, and Lucernaria, it 

 includes the Tabulate, Tubulose, and Rugose Corals, which Milne 

 Edwards and most other zoologists have hitherto associated with the 

 Polypi. "With reference to the systematic position of the Eugosa 

 vol. I. — x. H. r. 3 L 



