148 Royal Society: — 



and that of a Stylasteracean dredged off the Meaugis Islands in 

 500 fathoms. 



Literature of the Subject. — Few original works relating to the 

 subjects treated of in this paper were available for reference on 

 board the ' Challenger.' A review of what has been able to be 

 gathered of the recent literatiu-e relating to the Tabulate and 

 Eugose Corals and the Alcyonarians is given, and also a history 

 of the various systematic arrangements to which the Tabulata and 

 Eugosa have been subjected. 



Professor Agassiz published his opinion as to the hydroid 

 affinities of the IMilleporidte in 1859 ("Les Animaux des Mille- 

 pores sont des Acalepheset non des Polvpes," Bibl.Univ.de Greneve, 

 Arch, des Sci., Mai 1859), and figured the animals of the Millepora 

 alcicornis in his ' Contributions to the Natural History of the 

 United states,' -vol. iii. plate 15. Pourtales observed the animals in 

 company with Agassiz. He says that one which he saw was 

 " shorter than they are represented to be in the figure, and had 

 five tentacular masses rather than tentacles." M. -Edwards con- 

 sidered Professor Agassiz's evidence as to the hydroid nature of 

 Millepora insufficient, as does also Professor Allman. 



Professors Claus. Pourtales, Verrill, and many other authors 

 accept Agassiz's conclusion with regard to the Milleporidse, but do 

 not accept his views with regard to the Eugosa. 



Professor Yerrill (f5illiman's American Journal, 1872, vol. iii. 

 pp. 187, 194) found that Pocillopora, a genus with extremely well- 

 marked tabulae, was a true Hexactinian, and showed that the pre- 

 sence of tabulae, the character relied on by Professor Agassiz, was 

 of little importance. Pourtales and L. Ludwig have come to 

 the conclusion that the tetrameral arrangement in the Eugosa 

 is merely apparent, and that the original arrangement in the 

 young coral was hexameral. Professor Martin Duncan arrived 

 at similar conclusions from the examination of Guynia annulata. 

 Kunth, however, still adheres to the tetrameral primary division. 

 Lindstrom, the first discoverer of the opercular apparatus of cer- 

 tain Eugosa, compares these structures with skeletal structures 

 of Primnoa. The latest paper on the classification of Corals is 

 by M. Dollfus (Comptes Eendus de I'Acad. des Sciences, t. Ixxx. 

 no. 10, 8 Mars 1875, pp. 681-683). M. Dollfus connects together 

 the genera Udiolites and Propora with Heliopora and Seriatopora 

 by means of Pocillojjora, considering all these to be Hydroids. 

 Favosites, with many other genera of Palaeozoic Corals, he considers 

 to be a Bryozoou. 



Methods employed. — The corals examined were hardened in 

 alcohol or chromic acid, decalcified, and cut into fine vertical and 

 horizontal sections. Sections of the hard parts were rubbed 

 down in the usual manner. Portions of Heliopora ccerulea were 

 also examined in the fresh state. 



On the. Structure of Heliopora caerulea. — Heliopora ccerulea Mas 

 found growing in abundance on reefs near Zamboangan at low- 

 tide. The polyps were never seen expanded, though pieces of the 



