REPORT ON CORALS—HELIOPORID. 103 
Metuops EMPLOYED. 
The specimens of Heliopora and of Sarcophyton examined were hardened in absolute 
alcohol, being placed in it in the living condition. Portions of them were subsequently 
decalcified in weak hydrochloric acid, imbedded in wax in the usual manner, and cut into 
sections. The sections were examined partly in glycerine, partly in Canada balsam, after 
being rendered transparent by means of oil of cloves. Some sections were stained with 
carmine. Some portions of Heliopora were placed whilst living in a solution of chromic 
acid, and slowly decalcified whilst in the solution by the addition of a few drops of hydro- 
chloric acid from time to time; these yielded some results which were not obtainable 
from specimens hardened in alcohol and more rapidly decalcified. Sections of small area 
were also forcibly cut from the undecalcified hardened corals in order to show the relations 
of the hard parts to the soft, and separate polyps were removed from their calicles with 
the point of a scalpel and examined whole in glycerine; portions of the tissues of 
Heliopora were also observed in the fresh condition. For examination of the structure 
of the hard calcareous tissues, fine sections were prepared by grinding in the usual 
manner. 
Observations on [Heliopora caerulea in the living condition. 
Heliopora cerulea was found growing in abundance on the reefs fringing the shore 
of the small island of St Cruz Major, which lies opposite the harbour of Samboangan, 
Mindanao, Philippine Islands. The coral grew in about two feet of water at low tide. 
It has a uniform light chocolate-colour when fresh and living. Although I transferred 
portions of the living coral to a glass vessel under water, so that they never came in con- 
tact with the air, I did not succeed in getting the polyps to expand; and I have 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 por- 
tions 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. 
Structure of the Corallum of Heliopora cerulea. 
The genus Heliopora was formed by Blainville (Manuel d’Actin., p. 392). It is thus 
characterised by Milne-Edwards (Hist. Nat. des Corall., t. iti. p. 230) :-—* Corallum massive, 
