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Remarks on the Affinities of Rhabdopleura. By E. 

 Ray Lankester, M.A. (With Woodcuts.) 



The memoir of Mr. G. O. Sars, reproduced from his own 

 Eughsh publication in the preceding pages, is of very great 

 interest, in that it clearly makes known to us the anatomy of 

 the remarkable genus established by Allman in this Journal, 

 with so much shrewdness on the examination of a few spirit 

 specimens. I desire to take this opportunity of pointing out 

 that the supposed relation of Rhabdopleura to the Hydrozoa, 

 supported above by Sars, is not really indicated by the facts 

 he has adduced. There is, I venture to affirm, on the 

 contrary, no important feature in which Rhabdopleura really 

 approximates to the Hydrozoa. It is separated by a huge 

 gulf from the Diploblastica, from the animals devoid of true 

 body cavity, and possessing extensive gastric ramifications. 



The real and great interest of Rhabdopleura seems to me 

 to consist in this, that it tends to upset that classification 

 which has been adopted by such distinguished investigators 

 as Gegenbauer and Haeckel. These authorities remove the 

 Polyzoa from association with the MoUusca, and place them 

 in the central or proliferous ancestral group. Vermes. Huxley 

 and Allman, on the other hand, remain staunch to Milne- 

 Edwards' arrangement of the Polyzoa under the MoUuscan 

 sub-kingdom. 



Though one class of the so-called Molluscoidea, namely, 

 the Tunicata, has to be removed from the MoUuscan family- 

 tree in consequence of recent researches — if our classifications 

 are to have any genealogical signification, and very few 

 persons doubt that they must have such a signification — yet 

 there really has not been a serious attempt to contravert 

 those reasons which have been assigned, especially by Allman, 

 for associating the Polyzoa with the MoUusca. In passing I 

 may say that still less is there reason for removing the 

 Brachiopoda from such association. In Rhabdopleura we 

 have a form which binds the Polyzoa fast to the MoUuscan 

 series, and with the Polyzoa undoubtedly go the Brachiopoda, 

 as the recent observations of Morse on the development of 

 Terebratulina, and my own on Terebratula vitrea, show. 



When it is once admitted, as it may be most fully, that 

 the great family-tree of the MoUusca has developed directly 

 from the Vermes, and more largely than any other of the 

 four great trees springing from Vermian ancestors has re- 

 tained the essential organization of its ancestors in a primitive 



