REPORT ON CORALS—HYDROCORALLINE, 31 
The hard tissues are transversed in all directions by fine capillary branching canals which 
are provided at intervals with numerous spherical cavities attached to them laterally 
(Pl. XIV. figs. 6, 8). In Millepora alcicornis, from Bermuda, in which the ccenosteum is 
comparatively soft and cancellar, borings of the parasites could only here and there be 
detected. When set free by acids the organisms are seen to consist of ramifying 
mycelial threads, with abundance of fructification. Their structure has been described 
at length by Professor Duncan. It is remarkable that they have a distinctly green colour. 
They are not confined to the calcareous structures, but in Millepora nodosa at least, 
occur also in abundance amongst the soft superficial tissues ; and it appears probable that 
they become included within the calcareous tissue by the calcareous matter being 
deposited around them as the ccenosteum is extended by growth. 
SECTION IL—ON THE STRUCTURE OF THE STYLASTERID. 
WITH A LIST OF ALL THE SPECIES OF THE FAMILY AT PRESENT KNOWN, AND 
DESCRIPTIONS OF SOME NEW SPECIES OBTAINED BY H.M.S, CHALLENGER. 
INTRODUCTION. 
In the Proceedings of the Royal Society, No. 172, 1876, I published a preliminary 
note on the present subject, and gave a short account of the results which I had arrived 
at from a somewhat hurried examination of the material at disposal. After this short 
account had been written, | devoted my time during the remainder of the homeward 
voyage of H.M.S. Challenger to the further study of the structure of the Stylasteridz, and 
the preparation of drawings illustrating it ; I have supplemented this by additional work 
in England, and the results are embodied in the present paper.’ The main part of 
the specimens of Stylasteridxe, from the study of which the anatomical details were 
determined, was obtained at a single haul of the trawl-net taken on February 14th, 1876, 
in lat. 37° 17’ S., long. 53° 52’ W., off the mouth of the Rio de la Plata, in a depth 
of 600 fathoms. The specimens then obtained included six genera of the family 
Stylasteride. They were in most excellent preservation, although they had heen slowly 
raised from the bottom, and in all the genera but one the generative organs were in full 
1The greater part of this present treatise is a reprint of the Croonian Lecture for 1878, On the Structure of the 
Stylasteride (Phil. Trans. Roy. Soc., part 2, 1878, p. 425), which was published in advance in the Philosophical Transac- 
tions by the permission of the Lords Commissioners of the Treasury. 
