REPORT ON THE ANTIPATHARIA. 73 



Is 'anthidaj amongst the Actiniaria have a similar axis, which in some cases, too, becomes 

 tubular. In Savaglia the colonies are larger and more important, and apparently the 

 sclerenchymatous sheath may be continued beyond the foreign substance which at first 

 forms its support, but in both cases the growth is at first parasitic. In the Zoanthidas it 

 apparently never ceases to be so. On the other hand the zooid of Savaglia does not 

 appear related to that of the Zoanthidse. R. Hertwig and Erdmann regard the alterna- 

 tion of macro- and microsepta as the most prominent feature of the latter group, and this 

 condition does not obtain in Savaglia. I have not been able to make sections of this 

 species, and am unable to add anything to the researches of Lacaze Duthiers. 

 Temporarily I have retained it amongst the Antipatharia, but it must be regarded as a 

 genus quite apart, and one which may ultimately be included in the Actiniaria. 



With the exception of Savaglia the most constant feature of the Antipatharia is the 

 presence of spines on the axial horny sclerenchyma. This is a feature which, so far as I 

 know, is only shared, and then in a modified manner, by one other genus of Anthozoa, 

 viz., Acanthoisis, Wright and Studer. In this genus, the only one amongst the Gorgonidse 

 which appears to approach the Antipatharia in this respect, the axis consists of alternating 

 calcareous nodes and horny internodes ; the internodes have the surface raised in ridges, 

 which are dentate. 1 Next in importance, and with the additional exception of the 

 Dendrobrachiidaa (also at present limited to one species), we may consider the simple 

 nature of the tentacles and the absence of a sphincter muscle, as a necessary result of 

 which the tentacles cannot be covered by the upper portion of the body-wall. The 

 former feature was until recently supposed to separate sharply the Zoantharia from the 

 Alcyonaria. We now know, however, that certain families of Actiniaria (Sarcophianthidse 

 and Thalassianthidse) have the tentacles branching or bushy, and thus approach the 

 Alcyonarian type. Dendrobrachia, too, amongst the Antipatharia has pinnate tentacles. 

 The presence of a sphincter muscle, though frequent in the Actiniaria, is not a constant 

 feature. The group includes all grades of differentiation in this respect. Further, and 

 again with the exception of Savaglia, the arrangement of mesenteries in the Anti- 

 patharia is constant, and in all genera yet described (? Dendrobrachia) they may be 

 reduced to one type. 



The characters which I have considered of generic value refer chiefly to the form of 

 zooid and the number and relations of the mesenteries. The latter have been found to 

 vary from twelve to six in the Antipathidse. The following is the arrangement at 

 present proposed : — 



1 Wright and Studer, Challenger Alcyonaria, Zool. ('hall. Exp., pt. lxiv. (vol. xxxi.) p. 45, pi. viii. tigs. 1, In, 16. 



(ZOOL. CHALL. EXP. PART LXXX. 1889.) Llll 10 



