. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. 356 Mr. W. J. SoUas on the Genus Catagma. The longitudinal sections of the spicules generally exhibit a number of opaque dots, usually irregularly dispersed ; so that one of them occurring in a transverse section would simiilate an axial canal cut through. This makes one less sure that axial canals really exist in these spicules ; but since the dots sometimes take a linear arrangement in the longitudinal sec- tions (PI. XIV. fig. 16), they may, after all, indicate axial canals
. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. 356 Mr. W. J. SoUas on the Genus Catagma. The longitudinal sections of the spicules generally exhibit a number of opaque dots, usually irregularly dispersed ; so that one of them occurring in a transverse section would simiilate an axial canal cut through. This makes one less sure that axial canals really exist in these spicules ; but since the dots sometimes take a linear arrangement in the longitudinal sec- tions (PI. XIV. fig. 16), they may, after all, indicate axial canals which have been partially filled up. Relative Position in the Fibre of the two kinds of Spicules. The filiform spicules chiefly occur in the outer part of the fibre, often forming the exterior third on each side, though sometimes less and sometimes, on the other hand, more of it, in some cases apparently occupying nearly the whole of the fibre almost to the exclusion of the other kind of spicules. Fig. Section (partly diagrammatic) across fibres near the external surface of Catagma macroporics. ( X 70.) a, uniaxial spicules; b, transverse section of a multiradiate; c, echinating multiradiate spicules; d, interspace of a mesh, lined with granular material and filled up with calcitic crystallization. The multiradiate spicules are usually axial in position, forming a core which is about one third the diameter of the whole fibre, though sometimes wider. This core looks, at first sight, like a congeries of irregular calcite crystals ; but upon very careful analysis by the microscope it is seen to consist of circular and. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original London, Taylor and Francis, Ltd
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