Elementary text-book of zoology, general part and special part: protozoa to insecta . elementarytextbo00clau Year: 1892 Fig. 160.—Silex bodies from different siliciona Sponj^cs. a, Silex needle from Syiongilla, inside the cell, b, Amphidisc of a gemmule of SpongiUa. c, Anchor from Ancorina. d. Hook from Esperia. c, Star from ChondHlla. f, Anchor from Euplectella aspcrgillum, g, h, needle rays from the same, i, Six-rayed needle from the same, with central canal. structure is commonly known as the coll; collared cells.] P and the cells the Fig. 161.—Portion of the exter- nal layer of Spotigi
Elementary text-book of zoology, general part and special part: protozoa to insecta . elementarytextbo00clau Year: 1892 Fig. 160.—Silex bodies from different siliciona Sponj^cs. a, Silex needle from Syiongilla, inside the cell, b, Amphidisc of a gemmule of SpongiUa. c, Anchor from Ancorina. d. Hook from Esperia. c, Star from ChondHlla. f, Anchor from Euplectella aspcrgillum, g, h, needle rays from the same, i, Six-rayed needle from the same, with central canal. structure is commonly known as the coll; collared cells.] P and the cells the Fig. 161.—Portion of the exter- nal layer of Spotigilla with the pores, P (after Luberkiihn). able to close themselves, The thick layer in \vhich the skeletal spicules are produced consists of a hyaline matiix, in which irregularly branched or spindle-shaped amoeboid cells are embedded, and may be regarded, like the gelatinous substance of the Acalej^ha, as mesoderm, while the external, clearly defined, flat epi- thelium (also in the Asconia, Leucosolenici) is to be considered as ectoderm. The pores or inhalent openings so cha- racteristic of the Sponge body are in reality only intex'cellular spaces, and are vanish and be replaced by new pores, which arise by the separation of one cell from another (fig. 161). * Upon this ground Clark declared the Sponges to be nearly allied to Ihfl Flaqdlata, and regarded them as great colonies of the latter.
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