366 



DISCOVERY REPORTS 







Fig. 54. Embryonic development in certain species of Tetraxonid sponges. 



a~d, Callyspongia flabeUata, sp.n. 



«, 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. 



