REPORT ON CORALS — HYDROCORALLIN^E. 17 



Professor Glaus' Grundziige der Zoologie, 3 te Auflage, 1874, p. 226, rightly placed the 

 Milleporidse with the Hydroids. 



General Nelson's figures (published by Professor Martin Duncan 1 ) of the animals 

 of Millepora alcicornis do not seem to be of very much value. They appear to represent 

 imperfect conceptions of the dactylozooids. In September 1878 Mr William North 

 Rice published a short account of his observations of the living polyps of Millepora 

 alcicornis at Bermuda. He saw apparently only the dactylozooids, of which he gives 

 outline figures. The tentacles are not disposed in them in whorls of four as figured by 

 General Nelson, but more as in Millepora nodosa as described by me. His results go to 

 confirm my own in several points of importance. 2 



Methods Employed. 



Sections of the corallum were prepared in the usual manner by grinding. Portions 

 of the living coral were placed in various solutions for subsequent examination, viz., in 

 absolute alcohol, chromic acid, and glycerine. Portions were further treated with osmic 

 acid, and then transferred to glycerine or absolute alcohol. Fragments of the hardened 

 coral were subsequently decalcified with hydrochloric acid, and the residual soft struc- 

 tures were either mounted entire for examination, or cut in the usual manner into fine 

 vertical and horizontal sections. The sections were stained with carmine or magenta. 

 The specimens hardened in osmic acid, and decalcified after subsequent immersion in 

 absolute alcohol, yielded the best histological results. Those which had been hardened 

 in absolute alcohol alone gave the best results as to the coarser anatomy. The specimens 

 preserved directly in glycerine preserved most perfectly the forms of the several histo- 

 logical elements, and especially yielded good preparations of the thread-cells, preparations 

 of which are best procured by grinding up between two glass slides a zooid and its 

 immediately surrounding calcareous bed, removed with the point of a scalpel. A view of 

 the structure unacted upon by acids is thus obtained. The specimens placed in chromic 

 acid were of little service for sections, owing to a thick crystalline deposit of sulphate of 

 lime which formed upon them in the solution ; but they showed best, on the under 

 surface of the decalcified superficial film, the ramifications of the soft parts of the 

 hydrophyton. Dr G. von Koch's 3 method of cutting sections of corals in which both the 

 hard and soft parts are displayed in the same preparation will no doubt yield excellent 

 results in the case of the Hydrocorallinse. 



1 Ann. and Mag. Nat. Hist., vol. xvii. p. 354. 



2 Win. North Rice On the Animal of Millepora alcicornis, American Jonrn. of Science aud Art, vol. xvi., Sept. 

 1878, p. 180. 



3 For an account of the method, see Zool. Anzeiger, Bd. i. 



(ZOOL. CHA1L. EXP. — PAET VII. — 1880.) G 3 



