. The development of Renilla. Sea pansies; Ctenophora; Cnidaria; Corals. 778 DR. E. B. WILSON ON THE DEVELOPMENT OF RENILLA. College, for examination with the polariscope. He kindly undertook to examine them, and the following statement of his results is quoted verbatim:— " I find the smaller spicules to polarise perfectly and very brightly, and if the spicules are a carbonate, it is probably aragonite rather than calcite, because of the bright colour it affords. " Each spicule is made up of a core of crystalline material surrounded by a thin layer of non-polarising matter, and this
. The development of Renilla. Sea pansies; Ctenophora; Cnidaria; Corals. 778 DR. E. B. WILSON ON THE DEVELOPMENT OF RENILLA. College, for examination with the polariscope. He kindly undertook to examine them, and the following statement of his results is quoted verbatim:— " I find the smaller spicules to polarise perfectly and very brightly, and if the spicules are a carbonate, it is probably aragonite rather than calcite, because of the bright colour it affords. " Each spicule is made up of a core of crystalline material surrounded by a thin layer of non-polarising matter, and this by an outer layer, slightly thicker, and also of equal thickness, which polarises as does the " The crystalline axes uniformly run parallel to the long and short diagonals, as in the sketch, so that the core is a crystal probably of the rhombic system, and the outer layer is controlled in its position by this core and has parallel axes with it. " The larger spicules I can best explain by saying that for a moment, on examining the slides, I supposed the small ones to be cross sections of the former (larger) ones. They are like bones filled with niarrow under the microscope, the bone and the marrow representing the core and the outer layer of the small ones, and these being separated by an amorphous (in one case there were two amorphous layers) layer. In tliis case, the long axis of the spicule is a crystallographic axis. And bone and marrow are orientirt ; From this, the very interesting fact appears that the spicules are formed by a true process of crystallisation, though the form and structure of the crystals are modified, probably by reason of their deposition in an organic viscous medium. This point, as noted below, is one of much theoretical interest. In Leptogorgia the characteristic spicules appear in the ectoderm soon after the attachment of the larva. They are quite irregularly distributed, and extend up into the bases of the tentacles. No
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Keywords: ., bookcentury1800, bookdecade1880, bookpublisherlondo, bookyear1882
