TUBULARIA. 399 



Elircnberg's reform consisted in a (lisnicinliernicut of the genus Tiihiilaria as tlien accepted 

 into two groups, one of wliicli included the simple and the other the branched forms. Tiie 

 former he retained under the old name of Tubularia, while for the latter he constituted a new 

 genus under the name of EuJcndri/im. 



Though Ehrenberg did not strike upon the true grounds of n philosophic revision when 

 he selected as the fundamental character of his proposed groups the simple or branched condition 

 of the hydrocaulus, neglecting the far more important characters found in the form of the 

 hydranth, and the presence of two circlets of tentacles in Tubularia, while there is only a single 

 one in Eudendrium, his establishment of the genus Eudendrium as distinct from Tubularia, never- 

 theless led the way to more accurate definitions of the two groups, and tiius became a most 

 important step in the systematic zoology of the Hydroida. 



There is no one to whom we are so much indebted as to Agassiz for a knowledge of this 

 beautiful genus. He has made some of the North American representatives of it the subject of 

 laborious and conscientious study, and has illustrated his researches by the very finest hydroid 

 iconography in existence. I am unable, however, to accept in all points the systematic dismem- 

 berment of the genus Tubularia, as proposed by the celebrated zoologist who has adopted America 

 as his coimtry. 



The genus Tubularia of modern systematists has been broken up by Agassiz^ into four 

 separate genera, for one of which he retains the name of Tubularia, while for the three others he 

 proposes respectively the designations of Parypha, Tkamnocnidia, and Eclopleura. Agassiz gives 

 no technical diagnosis of any of those genera, and it is by no means easy to discover the 

 characters upon which he would chiefly rely as the grounds of his division ; but from my own 

 knowledge of the European species, which he separates from Tubularia, as well as from the very 

 detailed descriptions and beautiful figures of the American species, which he now for the first 

 time records, and refers to his new genera, I can find only in one of these forms, namely, the 

 Tubularia Dumortieri, of Van Beneden, characters which would, in my opinion, justify the 

 proposed dismemberment. Eor Tubularia Dumortieri Agassiz constitutes a new genus, under 

 the name of Eclopleura, and relying on Van Beneden's account of this hydroid, I willingly follow 

 Agassiz in regarding it as the representative of a separate genus ; but the only common character 

 of importance by which Pari/jjha and Tkamnocnidia are separated from Tubularia, would seem to 

 be the non-development of distinct gastro-vascular canals in the sporosacs of the species referred 

 by Agassiz to these genera, while they are present in the sporosacs of those species to which 

 he would restrict the name of Tubularia. 



Now, I cannot admit that the apparent absence of these canals, if unaccompanied by any 

 other ditference of importance, ought to be regarded as affording a character which would justify 

 the construction of a separate generic group ; for besides the practical objection that it is fre- 

 quently very difficult to detect them even when present, it should be borne in mind that though 

 they may exist in the younger sporosac, they may entirely disappear before the contents of 

 the gonophore are discharged, a fact which Agassiz himself notices in the case of his Tubularia 

 Contiioni/i. 



Again, between Panjpha and Thavinocnidia, the only diff'erence alleged is in the structure 

 of the tentacula-like processes, which occiu- upon the distal end of the sporosac. I believe, how- 



' ' Contr. Nat. Hist. U.S./ vol. iv. 



