ANTHOZOA, ALCYONARIA AND ZOANTHARIA. 733 



Clavularia, Hickson, P. R. S. xl. 1886, p. 322; von Koch, M. J. vii. 1881. 

 Sarcodictyon, Herdman, Proc. Roy. Phys. Soc. Edinburgh, Session 1883-84. Tubi- 

 pora, Hickson, Q. J. M. xxiii. 1883. Sarcophyton, Moseley, Challenger Reports, ii. 



1 88 1, p. 117 ; Corallium, de Lacaze Duthiers, Histoire Nat. du Corail, Paris, 1864 : 

 cf. Moseley, Q. J. M. xxii. 1882. Isis Neapolitana, von Koch, M. J. iv. 1878; 

 Gorgonia verrucosa, Id. ibid. : various Axifera, Id. Mitth. Zool. Stat. Naples, iii. 



1882. Pennatulidae, Kolliker, Challenger Reports, i. 1880 : Id. Abhandl. Senckenb. 

 Ges. vii. 1879; viii. 1872; Report on the Oban Pennatulidae, A. M. and W. P. 

 Marshall, Birmingham, 1882; Pennatulida dredged by H.M.S. Triton, A. M. 

 Marshall, Trans. Royal Soc. Edinburgh, xxxii. pt. i, Session 1882-83; Umbellula, 

 Kolliker, Festschrift zur Feier des 25-jahrigen Bestehens d. phys. med. Ges. in 

 Wurzburg, 1874; cf. Lindahl, A. N. H. (4), xiii, 1874, and von Willemoes-Suhm, 

 ibid. xv. 1875. Renilla, Wilson, Ph. Tr. 174, 1884. Heliopora, Moseley, Challenger 

 Reports, ii. 1881. 



Skeleton, von Koch, M. J. iv. 1878; Id. M. J. vii. p. 484; Id. Biol. Central- 

 blatt, ii. 1882-83. Development in Gorgonia, Id. Mitth. Zool. Stat. Naples, iii. p. 550. 

 Skeleton in Corallium, &c., Nicholson, A. N. H. (5), xiii. 1884. 



Siphonoglyphe, Hickson, Ph. Tr. 174, 1883. Mesenterial filaments, Wilson, 

 Mitth. Zool. Stat. Naples, v. 1884; ditto of Xenia and Sympodium, Haacke, Z. A. 

 vii. 1884. 



Phosphorescence of Pennatulidae, Panceri, Atti Ac. Napoli, v. 1873 ; cf. Q. J. M. 

 xii. 1872. 



Development of Renilla, Wilson, Ph. Tr. 174, 1883; of Clavularia and Sympo- 

 dium, Kowalewsky and Marion, An. Mus. Nat. Hist. Marseilles, i. 1883. 



Classification, von Koch, M. J. iv. 1878, p. 474; Hickson, Ph. Tr. 174. 

 p. 699, 



SUB-CLASS 2, ZOANTHARIA ( = Hexacoralla). 



Anthozoa which may be simple or colonial, and in the latter case fur- 

 nished as a rule ^vith either an organic or calcareous continuous skeleton 

 derived from the basal ectoderm. The tentacles are usually simple. They are 

 arranged in one or more circles, the members of a circle or of different circles 

 being often dissimilar in size. The mesenteries and the retractor muscles are 

 never disposed as in Alcyonaria : the former are very generally paired, and 

 then tentacles may correspond to the inter- as well as to the intra-septal spaces. 

 The number of both tentacles and mesenteries is very generally, biit not uni- 

 versally, some multiple of six 1 . One or two siphonoglyphes are of ten present. 

 Dimorphism is known only in one instance. 



1 The Zoantharian mesenterial filaments are described on p. 241. It has been suggested by 

 Wilson that the median lobe is of ectodermic, the two lateral lobes of endodermic origin. Histology, 

 as pointed out by Fowler (Q. J. M. xxvii. p. 8), points in the opposite direction. But there is one 

 difficulty in the way of any such derivation, viz. the filaments of incomplete mesenteries are con- 

 structed on the same type as are those of complete. As the former set of mesenteries are never in 

 contact with the stomodaeum, it is not possible for them to acquire a band of ectoderm cells. 

 See on Alcyonarians, p. 730, ante. 



