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Show 574 DR. R. VON LENDENFELD ON THE SYSTEMATIC [Dec. 21, 1. Ordo CALCISPONGLE, Blainville. The only Order, with the characters of the Subclassis. II. Subclassis SILICEA, Lendenfeld. Spongiae with a skeleton composed of siliceous spicules and their descendants with horny aspiculous skeleton and askeletous forms. 2. Ordo HEXACTINELLIDA, O. Schmidt. Silicea with soft mesogloea. Supporting skeleton often strengthened with siliceous cement. Spicules triaxon. 3. Ordo CHONDROSPONGLE, Lendenfeld. Silicea in which the toughness is achieved by the mesogloea or mesodermal ground-substance becoming cartilaginous, whilst the spicules remain isolated. Spicules tetraxon, monaxon (tylostylus), or absent; generally corticate. 4. Ordo CORNACUSPONGIAE, Vosmaer. Silicea "with soft mesogloea or mesodermal ground-substance; the supporting skeleton, composed of bundles of monaxonid not tylostyle spicules, is strengthened by spongin, which cements the spicules. These may disappear altogether, and the skeleton is then composed of spongin with or without foreign bodies. The skeleton rarely disappears altogether. Having thus divided the Class Spongiae into four Orders, we may proceed to the further division of tbe Orders into Families. I. Ordo CALCISPONGLE, Blainville. This Order has been divided by Haekel (627-629) into the well-known three families Ascones, Leucones, and Sycones, with seven genera in each. Polejaeff (1179) has divided tbe group into two Suborders and replaced HackeFs genera by the older and wider genera of Grant and others. I (888) have tried to combine Hackel's and Polejaeff's classifications, and have added three new families to the existing ones. I have retained Polejaeff's terms for the two Suborders, but have altered their meaning. In some Calcareous Sponges the whole of the entoderm consists of collar-cells. There are no entodermal pavement-cells in these forms. These constitute m y first Suborder Homocoela. In others the collar-cells are found in the ciliated chambers only, while the central gastral cavity is clothed with entodermal pavement-cells. I combine these forms in the Suborder Heteroccela. To the Homocoela belong besides Hackel's Asconidae, m y families Homodermidae and Leucopsidae. I acknowledge Eiickel's seven genera of the Asconidae. In the Heteroccela, Hackel's families Leuconidae and Syconidae together with Carter's Teichonidae and my family Sylleibidae are placed. |
