spongida, spongidæ, spongisæ

pl. [Mod. Lat., formed from spongia (q. v.).] 1. Zool .: A cla of Protozoa. Though not the lowest animals in organization, they were once relegated by some zoologists to the vegetable kingdom, but the botanists repudiated them, and with justice. They are e entially multicellular animals, in which the endodermal layers consist partly or wholly of flagellated collared cells. Most of them have a horny skeleton, composed of fibers, strengthened by siliceous or calcareous spicule (q. v.). The animal is of a gelatinous substance, investing the fibers of the skeleton during life, and traversed by canals connected directly or indirectly with the surface of the skeleton by many minute and a few larger apertures. The gelatinous part consists of an outer superficial layer of sponge particles. The inferior layer is of similar composition. The two are separated by a wide cavity communicating with the exterior by minute holes in the superficial layer; it is filled with water. In the floor of the cavity are many apertures, leading into canals, which ramify in the deep layer, and end in the floors of lofty funnels or craters. At the top of these are large exhalant apertures called oscules, whence currents proceed, while other currents set into the sponge by many minute holes, called pores or inhalant apertures. The pores bring in nutriment, while the oscules carry off excrementitious matter. They may also constitute an incipient breathing apparatus. Two reproductive proce es exist-one asexual, the other sexual. Nearly all sponges are marine. They occur more or le in every sea, and vary in size from a pin's head to four or even six feet high, and the same broad, but are largest and most numerous in the tropics. "They are ma ive, incrusting, ses sile, or stalked, globular, branched, tree-like, with the branches free or united laterally into a network; lamellar, irregularly or fan-shaped; tubular, vasiform, or labyrinthic, many of the forms presenting a close parallelism to corals." ( Sollas .) Orders: Myxos pong iæ, Calcispongie, Silicispongise, and Ceros pong iæ. [SPONGE, SPONGIA.] 2. Palæont.: From the Cam brian (?), or the Silurian (?), onward. Vitreous sponges occur abundantly in the Chalk. spong-i-form, a. [Eng. sponge, and form.] Resembling a sponge; sponge-like; soft and porous, like a sponge.