STRUCTURE AND RELATIONS OE CERTAIN CORALS. 
9T 
not seen them in that condition, although directly the coral was left at rest a swarm of 
a species of Leucodora, closely resembling Leucodora nasuta, which infests the coral 
and perforates it all over, expanded themselves at once. Most unfortunately I hardened 
in spirits portions of Heliopora taken from only one colony, as I did not suspect 
that the animal would prove to form unisexual colonies. This colony proved to be 
female ; and hence I have not seen the male generative organs of Heliopora. The only 
reference to the structure of the soft parts of Heliopora which I have found is a state- 
ment of Quenstedt ( l . c. p. 795), that Quoy says that the animals of Heliopora have 
more than twelve rays. 
Structure of the Corallum of Heliopora caerulea*. 
The genus Heliopora was formed by Blainville (Manuel d’Actin. p. 392). It is thus 
characterized by Milne-Edwards, l. c. p. 230 : — “ Corallum massive, lobulate, and rising 
in a tuft. Ccenenchym very abundant, and presenting at its surface a great number 
of rounded pores, disposed with regularity and separated by projecting papilliform 
grains. These grains are formed by the upper extremities of an equal number of 
cylindrical and vertical beams, which shut in tubuliform spaces, open above, and 
divided from space to space by cross partitions. Calicles circular. Septa very little 
developed, but distinct and 12 in number. Horizontal floors present and well developed. 
The genus is remarkable for its alveolar appearance and the tubular structure of the 
parenchym.” 
The coral is figured by M.-Ed wards, l. c. pi. 1. figs. 3 a, 3 b, 3 c. A drawing of the growing 
tip of a frond, much enlarged, will be found on Plate 9. figs. 16 and 17 of this paper. 
The following points require to be remarked concerning the structure of the corallum. 
The papilliform eminences described by M.-Edwards as covering the surface of the 
corallum spring from the points of apposition of the walls of several of the ccenenchymal 
tubes, very usually from the point of meeting of the mouths of four tubes (Plate 9. fig. 
17) ; here the hard tissue consists of a thickened vertical beam of calcareous matter, from 
which thin lamellar-like processes are given off, which form the walls between two con- 
tiguous tubes by crossing to join similar processes from the thickened beams situate at 
the point of apposition of these two tubes with the pair next succeeding them in the 
same direction. The narrow summits of the thin laminae forming the sides of the tubes 
fall short in their centres, by a considerable distance, of the level of the thickened 
masses from which they spring, but are rather excavated or hollowed out at these spots ; 
and it is across these excavations in the laminae that the deep system of canals passes in 
the fresh condition of the animals, by means of which the cavities of the tubes and 
polyps communicate freely with one another. The structure of the ccenenchym of the 
coral might be better described by saying that it consists of a series of tubes of circular 
* I regret extremely that I am unalble to refer to MM. Mils e-Edwards and Haihe’s papers, “Recherches 
sur les Polypiers,” Ann. Sc. Nat. iii., ix., xvi. 
