REPORT ON CORALS — HYDROCORALLIN^E. 15 



sending this chapter (on the Maclreporaria Tabulata) to the press, we learn that Professor 

 Agassiz has studied the mode of the organisation of the soft parts of the Milleporidae, 

 and has proved that these Zoophytes are not corals, but Hydroid Acalephs very nearly 

 related to the Hydractinise. Professor Dana shares the opinion of Professor Agassiz ; 

 and Agassiz believes that the Favositidse, as well as all other species of which the septa 

 are not continued vertically, ought to be considered strangers to the class of corals. But 

 the facts on which he grounds his opinion are not as yet sufficiently ascertained for us 

 to be able to form a critical opinion of their value; and, until more ample information 

 is received, we shall continue to rank the polyps in question according to the method 

 adopted in our former works." 



Professor L. Agassiz, in his Contributions to the Natural History of the United 

 States, 1 figured the animals of Millepora. He placed Millepora, Heliopora, Seriato- 

 pora, Pocillopora, and the whole of the Tabulate and Rugose Corals with the Hydroid 

 Acalephte. The principal distinction between these sections and true polyps relied on 

 by Agassiz, was as follows 2 : — " The pits into which the animals (i.e., of the Milleporidae 

 and their supposed allies) retreat have a horizontal floor extending from wall to wall, 

 and these floors are built successively one above another as the animal rises, the 

 radiating portion never extending vertically through successive floors. Not so with 

 the Actinoid Polyps, in which the radiating partitions extend from the top to the 

 bottom of the pit, while the horizontal floors, if they exist, extend only from one 

 radiating partition to another." Agassiz hoped that deep-sea dredgings would produce 

 additional evidence concerning the affinities of Millepora, and genera connecting more 

 closely the Rugosa and Tabulata with one another, and with the Acalephae, in the 

 shape of branching Heliopores and the like. (A letter concerning deep-sea dredgings 

 addressed to Professor Benjamin Pierce, Superintendent of the United States' Coast 

 Survey, by Louis Agassiz, Cambridge, Mass., Dec. 1871.) He had "not the remotest 

 doubt that the Tabulata were genuine Hydroids." 3 From the time when Agassiz's 

 observations on Millepora were published until the completion of the present paper, 

 no one made any examination of the structure of the soft parts of any of the members 

 of the Tabulata, with the exception of Professor Verrill who examined a Pocillopora, 

 and found it to be a true Zoantharian polyp with twelve septa and twelve tentacles 

 (Ann. and Mag. Nat. Hist., 1872, vol. ix., 4th series, p. 355, from Silliman's American 

 Journal, 1872, vol. iii. pp. 187-194, On the Affinities of Palaeozoic Tabulate Corals with 

 Existing Species). Quoy and Gaimard had, however, long before described the twelve 

 short tentacles of Pocillopora damicomis. 



Professor Verrill, in the paper above quoted, as he had done before, combated the 

 conclusions of Professor Agassiz that the whole of the Tabulata belonged to the Hydroid 



1 Louis Agassiz's Contribution to the Natural History of the United States of America, vol. iii. pi. xv. 



2 Ibid., p. 61. 3 Ibid., p. 121. 



