472 G. HERBERT FOWLER. 



Monauleas homologous with the pair marked 3, 3 in Fig. A, 

 p. 470, or with the other? Are the two mesenteries opposite 

 to this pair to be regarded as a ^'pair^' of directives, or do 

 they form two halves of separate pairs ? This latter query 

 applies at any point to the Holactinise.^ 



To crown the confusion, G. Y. and A. F. Dixon {' Proc, Roy. 

 Dublin Soc' [u. s.], vi) have described an abnormal Bunodes 

 with three pairs of mesenteries and three siphonoglyphs. 



It seems almost impossible in the present state of our know- 

 ledge to deny that an eight-rayed ancestor is common to the 

 several groups of the Anthozoa : the Alcyonaria and Edwardsiae 

 are permanently eight-rayed ; the Madreporaria, Hexactiniae, 

 and (without expressing an opinion on the points in dispute 

 between Boveriand van Beneden, we may add) the Ceriantheae 

 Jiave all yielded an eight-rayed resting stage in their ontogeny. 

 Nor is it perhaps a wanton use of the evidence to say that this 

 stage is the natural outcome of the earlier four-rayed condi- 

 tion, by further iuterradial specialisation in the first formed 

 four chambers. The evolution of a scyphistomoid ancestor 

 into the Lucernarise in one direction, the Anthozoa in a 

 second, the Scyphomedusse in a third, is very generally 

 accepted. The four mesenteries of the Lucernarise and 

 Scyphomedusse, like the more numerous mesenteries of the 

 Anthozoa, appear to have a threefold function : they carry (a) 

 digestive cells, (b) reproductive cells, (c) muscle cells; and it 

 is easy to conceive that, in a simple hydriform ancestor, a 



* I have cited these two groups merely to call attention to the absence of 

 evidence as to what constitutes homology between mesenteries, not because I 

 can accept them as groups of equal value with the Zoanthese, Cerianthese, 

 Edwardsise, and Hexactinise. In a discussion of these points we may fairly 

 utilise evidence drawn from the Madreporaria, which anatomically agree so 

 closely with the Hexactinise. Is Lophohelia, which is devoid of directives 

 (Fowler, 'Quart. Journ. Micr. Sci.,' xxviii, 1), to be placed with Mussa and 

 Euphyllia (Bourne, 'Quart. Journ. Micr. Sci.,' xxviii, 21) in a group of 

 Monaulic Madreporaria, while Amphihelia (Fowler, ' Quart. Journ. Micr, 

 Sci./ xxviii, 413), the very next genus, of which the corallum, the mode of 

 growth, and budding agree ahnost exactly with those of Lophohelia, remains 

 with the Hexactinic corals ? 



