. Fig. 54. Embryonic development in certain species of Tetraxonid sponges. a~d, Callyspongia flabeUata, «, embryo after first appearance of spicules; b, section of same, showing spicules in a tangential layer; c, spicules migrating inwards; d, latest stage observed, x 200. e-i, Plocamia gaussiana, Hentschel. e, embryo after first appearance of spicules; /, sector of same to show dermal epithelium and large granular cells of inner mass; w, first appearance of acanthostyli; //, sector of an embryo at a slightly later stage, showing columnar external layer; i, latest stage observed. e,g, h
. Fig. 54. Embryonic development in certain species of Tetraxonid sponges. a~d, Callyspongia flabeUata, «, embryo after first appearance of spicules; b, section of same, showing spicules in a tangential layer; c, spicules migrating inwards; d, latest stage observed, x 200. e-i, Plocamia gaussiana, Hentschel. e, embryo after first appearance of spicules; /, sector of same to show dermal epithelium and large granular cells of inner mass; w, first appearance of acanthostyli; //, sector of an embryo at a slightly later stage, showing columnar external layer; i, latest stage observed. e,g, h x 100,/, h x 250. j, Dictyociona discreta (Thiele). The latest stage observed, with dense axial core of plumosely arranged acanthostyli. x 200. k, Ashestospluma calyx, Hentschel. Embryo, x 160.
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Keywords: ., bookcentury1900, booksubjectocean, booksubjectscientificexpediti
