STRUCTURE AND RELATIONS OE CERTAIN CORALS. 
93 
Professor Verrill, in the paper above quoted, as he has done before, combats the con- 
clusions of Prof. Agassiz, that the whole of the Tabulata belonged to the hydroid polyps. 
This fact, he says, has only been proved for the Millepores : the remaining Tabulata 
should be joined with the true polyps, with which their relations are very near and 
intimate. The transverse partition-walls, the presence of which was held by Milne- 
Edwards and Haime as a characteristic distinction, are structures of a very low order, 
that occur in widely different forms , and are only brought about by the simultaneous 
emptying of the generative products from the radial chambers. Where the emptying 
is not thus periodically simultaneous, a separate transverse septum is formed in each of 
the chambers shutting off the space thus become vacant. True tabulae are found not 
only in Millepora and Pocillopora, but in Coelastrcea, Alveopora, and Aster ops dmmia r 
Columnctria is, apparently, closely allied to Coelastrcea , Favosites to Alveopora, Porites , &c» 
Ileliopora being shown to be an Alcyonarian, tabulae are proved to be present in forms 
still more widely different than is shown to be the case by Prof. Yerrill. The relation 
of Favosites and Columnaria appears now in a different light. 
The opinions expressed concerning Professor Agassiz’s relegation of the Tabulate and 
Rugose Corals to the Hydroids have been various. 
Professor Allman, in his ‘ Monograph of the Gymnoblastic or Tubularian Hydroids ’ 
(London, published for the Ray Society by Robert Hardwicke, 192 Piccadilly, 1871, 
page 3), refers to Professor Agassiz’s opinion on the subject as published in his ‘ Contri 
butions to the Natural History of the United States.’ He considers that since we are 
entirely ignorant of the generative system of the Milleporidse, it is much safer to wait 
for such verification as may be expected from further researches. He hesitates to 
include amongst the Hydrozoal orders the Tabulate and Rugose corals. Professor 
Allman (Quart. Journal Micr. Science, vol. lxii. pp. 394, 395) considers Edwardsia to 
occupy an intermediate position between Zoantharian and Alcyonarian polyps, and to 
be comparable with the extinct Rugosa, to which it corresponds in the numerical law of 
its body-segments. 
Count Pourtales (Illustrated Catalogue of the Museum of Comparative Anatomy 
at Harvard College, Cambridge, Mass. : No. iv. Deep-sea Corals, p. 56) places the 
Milleporidse with the Hydroids. He remarks, “ No observations have been made on 
Millepora since Professor Agassiz’s first announcement of the affinities of the Millepores 
with the Hydroid polyps twenty years ago. The polyps of Millepora are very difficult 
to observe, both because of their small size, and because they are killed by the shortest 
contact with air ; when obtained expanded, they contract on the slightest shake of the 
vessel containing them. I have succeeded but once in having a good view of one of 
the larger polyps of Millepora alcicornis in company with Professor Agassiz. It 
differed from the figure in the 4 Contributions to the Natural History of the United 
States,’ vol. iii. plate 15. fig. 1, in being comparatively shorter and having larger 
tentacles, or rather tentacular masses studded with lasso cells five in number instead of 
o 2 
