viii PREFACE. 



iharia, a large number may be referred, with greater or less 

 certainty, to the order of the Alcyonaria — a few forms being of 

 quite uncertain affinities. I have not, however, been induced 

 to think that the so-called " Tabulate Corals " are, to any 

 extent, referable to the Polyzoa ; ^ and I do not think that any 

 but the aberrant MilleporidcB can be at present regarded as 

 possessing Hydrozoan affinities. On many minor points I 

 have been led to form conclusions different from those that are 

 ordinarily held, and I have no right to expect that these will 

 be in all cases immediately or generally accepted ; while I 

 have the certainty that many of the results which I have 



^ Since this work has passed through the press, Professor Busk has published a 

 description and figures of the recent species of Heteropora referred to on p. 256, 

 giving to it the name of H. Neozelanica (Journ. Linn. Soc, vol. xiv., p. 724). Two 

 other living species have also been described by Mr W. Waters (Journ. Roy. Mic 

 Soc, June 1879). Mr Busk has shown that the walls of the zooecia and interstitial 

 tubes (" cancelli ") of H. Neozelanica are perforated by minute pores, a phenomenon 

 not unknown in species of the genus now extinct. In the comparatively limited 

 investigation of//'. Neozelanica made by me, these pores escaped notice. The con- 

 necting-pores just alluded to certainly admit of a comparison with the "mural 

 pores" of the Favositidce, but the comparison is not much closer in their case than 

 in the instance of the pores in the walls of species of Lepralia or Alecto. Nor does 

 their similar appearance and position prove these apertures to be absolutely homo- 

 logous. At any rate the likeness between the pores of Heteropora and the mural 

 pores of the FavositidcE is, to say the very least, no closer than the resemblance 

 between the latter and the apertures in the walls of such undoubted Actinozoa as 

 Porites and Alveopora. Giving due weight to this last consideration, and combining 

 this with the fact that the true zooecia oi Heteropora do not appear to be "tabulate," 

 while the typical " Tabulata" exhibit so many and such important points of affinity 

 with unquestionable living corals, both Alcyonarians and Zoantharians, I do not at 

 present feel inclined to alter the opinion which I have formed as to the Ccelenterate 

 nature of the FavositidcB, the ChstetidcE, and the Monticidiporidce. At the same 

 time, it is undeniable that there is a remarkably close resemblance between some of 

 these forms (and especially the Monticuliporoids) and Heteropora. This resemblance 

 is enhanced by the fact that one of the species of Heteropora described by Mr 

 Waters exhibits the usually chitinous surface-pellicle in a calcified and thickened 

 condition, thus reminding us forcibly of the state of parts in some of the species of 

 Favosites, and in various of the Monticuliporidcc. These resemblances, as above 

 pointed out, are counterbalanced by weighty points of dissimilarity; but they are 

 more than sufficient to make us await with the greatest interest any observations 

 upon the ajii/nal of Heteropora. 



