No. i.] MORPHOLOGY OF THE ACTINOZOA. 159 



Finally, as regards the Antipatharia, it must be confessed 

 that, notwithstanding the excellent Monograph by Brook ('89), 

 we are still far from able to estimate with any certainty their 

 past history. We know that they possess six principal mesen- 

 teries, and a corresponding number of tentacles. In some few 

 forms no additional mesenteries are developed, but in the major- 

 ity there are in addition four other mesenteries, which attain only 

 a slight development, and in Leiopathes these secondary mesen- 

 teries are six in number, making in all twelvemesenteries. 



It is possible to regard Leiopathes as representing the most 

 primitive arrangement in the group, upon which hypothesis 

 affinities with the Hexactiniae are suggested. Von Koch ('78), 

 on the strength of his investigation of the Actinian GepJiyra 

 Dohrnii, believed that he had found evidence of the manner in 

 which the Antipatharia had been derived from the Hexactiniae, 

 GepJiyra being one of those Actinians which locate themselves 

 on a relatively narrow cylindrical support (stems of Gorgonias, 

 etc.), which they surround by the base, secreting, as many other 

 forms do, a chitinous layer covering the support. Several 

 Actinians are now known, however, belonging apparently to 

 different families, which have this same habit, and the peculi- 

 arity should be regarded, as Andres ('84) endeavored to show, 

 as physiological and not phylogenetic. 



If the Hexactinian ancestry be maintained, it must be sup- 

 posed, as Von Koch has done, that a decided degradation has 

 taken place, for which there seems to be no evidence ; and, 

 furthermore, it must be shown that there is a paired arrange- 

 ment of the mesenteries. This it has so far been impossible to 

 do, since, owing to the very slight development of the longitu- 

 dinal muscles, no orientation of the mesenteries has been possi- 

 ble. Brook endeavors, however, to make out a case for this side 

 of the question by drawing a comparison between the degree of 

 development of the mesenteries of Leiopathes, and the manner 

 of development of the mesenteries of the Hexactiniae, as de- 

 scribed by Lacaze-Duthiers. I have already shown that the 

 order of succession of the mesenteries of the Bunodes studied 

 by Lacaze-Duthiers must be regarded as secondary, and it seems 

 improbable that the Antipatharia should follow this method, 

 instead of the more primitive one. 



Instead of this manner of regarding the question, it may be 



