REPORT ON CORALS— HELIOPORID.E. 103 



Methods 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 ccerulea in the living condition. 



Heliopora ccerulea 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 lierht 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 nasitta, 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 ccerulea. 



The genus Heliopora was formed by Blainville (Manuel d'Actin., p. 392). It is thus 

 characterised by Milne-Edwards (Hist. Nat. des Corall., t. iii. p. 230) : — " Corallum massive, 



