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Show 1880.] MR. H. N. MOSELEY ON SOME CORALS. 25 Jena1; but it is only lately that he has succeeded in preparing sections of corals so perfect as those exhibited. " The method is as follows :-The corals with all their soft parts in situ having been hardened in absolute alcohol, are placed in a solution of Canada balsam in ether, or in gum-sandarach in alcohol, or, better still, of copal in chloroform. After they have become thoroughly permeated by the resinous solutions, they are taken out and dried slowly until the masses become perfectly hard. The hard masses can now be cut into sections with a fine saw, and then rubbed down in the usual manner on a whetstone. The sections can be stained with carmine after being thus prepared, even without the removal of the resin ; but usually the tissues are stained in mass before being placed in the resinous solutions. All the soft parts thus become deeply tinged, and stand out in well-marked relief. The sections can then be mounted in fresh Canada balsam2. The sections received from Dr. von Koch certainly show a good deal which could not have been exhibited before ; and they are interesting, not only as illustrating a new point in the anatomy of corals, but because the method by which they are prepared seems to me to be likely to yield valuable results in the case of many other questions of microscopic investigation. It will be quite easy, for instance, by this means to prepare microscopic sections of injected bone in which the injected capillaries will be shown in their relations to the Haversian systems. Sections also could thus be prepared of the internal ear in which the hard and soft tissues will be preserved together, and the latter would not have been subjected to the deleterious action of the acids which are usually employed to decalcify the cochlea before it can be sliced with a razor. Sections through the undecalcified arms of starfish or crinoids prepared by this method could not but yield most interesting results, and similarly in the case of those Bryozoa which have a calcareous and opaque skeleton. I have sent specimens of Millepora and other hydroid corals to Dr. von Koch, and await with great interest the sections which he has promised to cut from these. It is even possible that by this means instructive sections for museum purposes of whole starfish or other animals might be cut and mounted on glass. " It has hitherto been supposed that the wall of all Madreporarian coralla is developed within the mesodermal layer of the wall of soft tissue of the animal. If this were the case, it would be expected that a simple layer of mesoderm and ectoderm would be found lying externally to the wall of hard tissue in transverse sections of a complete simple coral. Dr. von Koch, however, in his sections finds that this is not the case, but that there exist externally to the calcareous wall what he believes to be the continuation of the mesenteries, and also a series of cavities which are the continuation of the interme-senterial spaces. He thus comes to the conclusion that the wall of the coral-cup is not developed, as supposed, by calcification of the middle 1 Anatornie der Orgel-Koralle (Tubipora hemprichii). Dissertationzur Erlan-gung der venia docendi. Von Dr. Gc. von Koch. Jena, 1874. 5 2 For a detailed account of Dr. von Koch's process see the ' Zoologischer Anzeiger,' Jahrg. 1, p. 36. |