. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. 8 Mr. W. J. Sollas on Stauronema, a new In the centre of the node is a small and very definite circle, 4-To to -3-^-3 inch in diameter (figs. 1, 2, 3, c), which is produced by the section crossing at right angles a cylindrical tube, originally hollow, but now generally tilled with carbonate of lime; and from this radiate four similar cylindrical canals, one in the axis of each arm of the cross ; these, of course, are seen sideways and not end on, and ordinarily they are contin
. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. 8 Mr. W. J. Sollas on Stauronema, a new In the centre of the node is a small and very definite circle, 4-To to -3-^-3 inch in diameter (figs. 1, 2, 3, c), which is produced by the section crossing at right angles a cylindrical tube, originally hollow, but now generally tilled with carbonate of lime; and from this radiate four similar cylindrical canals, one in the axis of each arm of the cross ; these, of course, are seen sideways and not end on, and ordinarily they are continuous from one node to another, like the fibre in which they are excavated. As these appearances are to be seen equally in each of three sections taken at right angles to each other (figs. 1, 2, 3), it is^clear that our quadrilateral cross of fibre is really a sexradiate one (fig. 4), with its arms arranged about three Fie:. -6 Diagram of the network oi Stauronema, Scale 60 :1. a, sexradiate canal; b, sexradiate fibre. axes at right angles to each other, and that corresponding with the axes interiorly is a similar sexradiate hollow canal. Now this structure is exactly that which characterizes the rete of the Vitreohexactinellidge, and may be seen to perfection, with differences merely as to detail, in deciduous skeletons of Farrea and A'pTirocallistes. In these genera, as in the Vitreo- hexactinellidee generally, the skeleton is produced by a growth of siliceous matter over sexradiate spicules ; and in Farrea occa each node of the resulting network is a rectangular sexradiate cross of fibre, which has formed about a sexradiate spicule, which thus comes to occupy the centre of the fibre. In many vitreous hexactinellids the fundamental spicule is preserved imbedded in the siliceous fibre, which is thus originally solid; and which, as it is composed of the same material all through, without any difference of refractive index, cannot be distin-. Please note that these images are
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